- Email: [email protected]
Temperatures and ages of boxed beef packed and distributed in Canada
Meat Science 60 (2002) 401–410 www.elsevier.com/locate/meatsci
Temperatures and ages of boxed beef packed and distributed in Canada C.O. Gilla,*, T. Jonesa, K. Rahnb, S. Campbellb, D.I. LeBlancc, R.A. Holleyd, R. Starke a
Agriculture and Agri-Food Canada Lacombe Research Centre, 6000 C&E Trail, Lacombe, Alberta, Canada T4L 1W1 b Health Canada Laboratory, 110 Stone Road West, Guelph, Ontario, Canada N1G 3W4 c Agriculture and Agri-Food Canada Food Research Centre, Pavillion Jacqueline-Bouchard, University of Moncton, Moncton, New Brunswick, Canada E1A 3E9 d Department of Food Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2 e Agriculture and Agri-Food Canada Kentville Research Centre, 32 Main Street, Kentville, Nova Scotia, Canada B4N 1J5 Received 26 March 2001; received in revised form 18 June 2001; accepted 18 June 2001
Abstract Boxes of beef were examined when product was packed and when boxes were loaded out of five packing plants, when boxes were loaded into and loaded out of seven refrigerated warehouses, and when boxes were received and opened at 21 retail stores. At each stage of handling at each facility, the boxes to be examined were selected at random. For each selected box, the temperature of product at the centre of the box was measured, and the date of packing and the plant of origin were noted. When cuts were packed, the minimum, median and maximum temperatures were about 2, 6 and 18 C, respectively. Temperatures were successively lower when boxes were loaded out of packing plants, into warehouses and out of warehouses. When loaded out of warehouses, the minimum, median and maximum temperatures were about 2, 1 and 8 C, respectively. The ranges of temperatures were similar, but the median temperatures were about 2 or 1.5 C, respectively, when boxes were received at or were opened at retail stores. At packing plants and warehouses, the temperatures of manufacturing and ground beef were lower than those of cuts, but at the retail store the temperatures of all types of product were similar. When boxes were opened at retail stores, the minimum, median and maximum ages of cuts were about 2, 20 and 130 days, respectively; and the corresponding ages for manufacturing and ground beef were 2, 7 and 56 days, respectively. The data indicate that boxed beef is generally cooled to and maintained at temperatures within the range sought by the meat industry. However, cooling to chiller temperatures of product that is packed while warm can take several days; and some product is held for times that are excessive in view of the temperatures of boxed beef. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Beef; Temperatures; Ages; Distribution
1. Introduction In North America, most beef that will be offered for retail sale is dispatched from packing plants as a chilled, vacuum packed, boxed product. The boxed product is fabricated to retail forms by cutting or grinding, and is packed in retail trays in meat-cutting facilities at retail stores or, increasingly, at central cutting facilities from which it is distributed to retail stores (Farris, Deitrich, & Ward, 1991). Whether the meat is prepared for retail sale in store or centrally, it is likely to be displayed * Corresponding author. Tel.: +1-403-782-8113; fax: +1-403-7826120. E-mail address: [email protected] (C.O. Gill).
within a short time of being fabricated from boxed product (Gill, 1996). Thus, the microbiological condition, appearance and tenderness of the product offered for sale may all be substantially affected by the temperatures experienced by the boxed product and the times for which such product remains in the distribution system (Pearson, 1994). The time for which boxed beef is held, and the temperatures it experiences during distribution can greatly affect the quality of the product. Despite that published data on the temperatures and ages of boxed beef are relatively few, and derive from studies which mostly involved investigations of limited, well defined, distribution systems (Bøgh-Sørensen & Olsson, 1990; Gill & Jones, 1992). No reported survey of the temperatures
0309-1740/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(01)00151-6
402
C.O. Gill et al. / Meat Science 60 (2002) 401–410
and ages of boxed beef identifies the condition of product that is distributed through commercial systems which are sometimes complex. Therefore, to obtain better understanding of the temperatures and ages of boxed beef that is moving through commercial distribution systems, a survey was conducted of the temperatures and ages of boxed beef at production, storage and retail facilities across Canada.
2. Materials and methods 2.1. Ages and temperatures of product The temperatures of product in boxes of beef were determined at various stages of the distribution process. Each selected box of product was opened, and the probe of a thermistor thermometer (TraceableTM; Control Co., Friendswood, TX) was placed between packs of product at the approximate centre of the box. After allowing 2 min for equilibration of the probe, the temperature, to the nearest 0.1 C, was recorded. In addition to the type of product, the date when product was packed and the packing plant number were identified from the information on each box and were recorded. 2.2. Types of product Data were collected from nine types of vacuum packaged primal cuts, which were outside rounds, inside rounds, eyes of rounds, striploins, lip-on ribs, top butts, short cut clods, bone-in blades, and boneless blades. The names given to some of the cuts differed at different packing plants; and similar cuts were prepared in various forms, to conform with customers’ requirements. Differences in names and the exact forms of cuts were disregarded when selecting product for examination. In addition, data were collected from boxes of vacuum packaged trimmings or coarsely ground beef, depending on which of those types of product were available at each facility. 2.3. Collection of data Data were collected during the period June to November 1999, from product at five beef packing plants, seven refrigerated warehouses and 21 retail stores. At beef packing plants, data were collected from product being packed into boxes at the ends of the carcass breaking processes, and from boxes of product being loaded to refrigerated trailers. At refrigerated warehouses, data were collected from product being loaded from trailers into warehouses and from product being loaded into trailers for dispatch from the warehouses. At retail stores, data were collected from product at the times of its delivery to stores and at the times
of boxes being opened for the product to be fabricated to retail-ready items. At each stage of handling at each packing plant or warehouse, data were collected from boxes of product selected at random from those containing product of the selected types, but with no more than 10 boxes of product of one type being selected on any day, and with the examination of a total of no more than 100 boxes of product of one type. At each stage of handling at each retail store, data were collected from boxes of product, selected at random if the number of the available boxes of a type of product exceeded five, with no more than five boxes of product of one type being examined on any day, and with the examination of a total of no more than 25 boxes of product of one type. 2.4. Analysis of data Descriptive statistics for data sets were obtained using Microsoft Excel, version 4, statistical functions (Microsoft Corp, Redmond, WA, USA). Sets of data were tested for normal distribution using the Wilk–Shapiro test (Shapiro, 1990) in the UNIVARIATE procedure of SAS, version 6 (SAS Institute Inc., Cary, NC, USA). Median values for sets of data for product from individual packing plants at the times of boxes being opened at retail stores were separated using the Kruskal–Wallis test (Conover, 1971) in the NPAR1WAY procedure of SAS, version 6 (SAS Institute).
3. Results Most data sets were not normally distributed (P < 0.05), and for most sets the mean was greater than the median. At each stage of the distribution process, for sets of temperatures and ages for each of the nine types of primal cut, seven or more of the median values for temperatures differed by 40.7 C, and seven or more of the median values for ages differed by 43 days (Table 1). The types of cuts that gave values outside those ranges differed at each stage of the distribution process. The variations in mean temperatures and ages were similar, except for the stage of product packing when, at most, only four mean values for the temperatures of cuts of different types differed by 40.7 C. As the data for temperatures and ages of cuts of all types were similar, the data for all cuts were considered together in further analyses. The median and mean temperatures for boxes of primal cuts were lower at each successive stage of distribution from boxing at packing plants to exiting warehouses (Table 1). The median and mean temperatures were higher for primal cuts entering retail stores than for primal cuts exiting warehouses, but the median
403
C.O. Gill et al. / Meat Science 60 (2002) 401–410
Table 1 Ranges of the median, mean, minimum and maximum temperatures and ages of boxes of each of nine types of primal cut at six stages of the distribution of beef from packing plants to retail stores Stages of distribution
No. of boxes of each cut type
Total boxes
Temperature ( C) Median
Mean
Age (days) Min
Max
Median
Mean
Min
Max
0
0
0
0
Boxing
386117
4083
6.60.6
7.2 1.2
2.2 0.5
15.4 3.2
Exit packing plants
31888
3291
2.70.5
3.1 0.7
1.3 1.0
9.6 3.0
2 2
3.92.7
0
2413
Enter warehouses
554104
5115
1.60.5
1.9 0.3
1.8 0.4
10.1 2.5
7 1
7.30.8
0
3922
Exit warehouses
46950
4430
0.80.2
1.1 0.3
1.7 0.3
6.2 1.8
14 2
13.41.9
0 or 1
5131
Enter retail stores
15978
1278
1.50.8
1.6 0.6
1.4 0.4
4.7 1.0
13 3
15.44.0
54
7848
Exit store chillers
395128
1745
1.10.5
1.1 0.4
1.4 0.6
5.0 0.5
21 4
22.16.3
53
8050
and mean temperatures for primal cuts exiting the storage chillers at retail stores were similar to those for primal cuts exiting warehouses. The minimum temperatures for boxes of primal cuts were progressively lower at the successive stages of distribution of boxing, exiting packing plants and entering warehouses, but at later stages the minimum temperatures were similar to those for cuts entering warehouses. The maximum temperatures for boxes of primal cuts were lower for cuts exiting packing plants than for cuts at the times of boxing. The maximum temperatures of primal cuts entering warehouses were similar to the maximum temperatures for cuts exiting packing plants, but maximum temperatures of cuts were progressively lower at the subsequent, successive stages of exiting warehouses and entering retail stores. The maximum temperatures of cuts exiting chillers at retail stores were similar to the maximum temperatures of cuts entering retail stores. At successive stages of the distribution process, the median, mean and maximum ages of boxes of primal cuts increased, and the ranges of the median and mean ages of the different cuts widened (Table 1). At all stages of distribution the oldest cuts were striploins. The minimum age for cuts of all types for the stages of distribution up to and including entering warehouses was 0 days. The minimum age for cuts exiting warehouses was 1 day, except for bone-in blade cuts, for which the minimum age was 0 days. The minimum ages for cuts of different types entering retail stores or exiting retail chillers were mostly between 2 and 6 days. For manufacturing and ground beef, at each stage of the distribution process before delivery to retail stores, the median and mean temperatures were lower than the corresponding temperatures for any type of cut at the same stage of distribution. At all stages of distribution the median and mean ages of manufacturing/ground beef were less than the corresponding ages for any type of cut at the same stage of distribution.
At the times manufacturing or ground beef were placed in boxes, the temperatures of the former product were generally >2 C, while the temperatures of the latter product were < 2 C. The median and mean temperatures for manufacturing/ground beef were lower for product exiting packing plants than for product at the times of boxing (Table 2). Median temperatures were similar for manufacturing/ground beef exiting packing plants, entering warehouses or exiting warehouses, but mean temperatures for product entering or exiting warehouses were less than the mean temperatures for product exiting packing plants. Median and mean temperatures were higher for product entering retail stores than for product exiting warehouses, but median and mean temperatures were less for product exiting chillers at retail stores than for product entering retail stores. The minimum temperature of manufacturing/ ground beef was lowest for product at the times of boxing and highest for product exiting chillers at retail stores. The maximum temperatures for product at the times of boxing and exiting packing plants were similar. The maximum temperatures at the latter stages of distribution were lower than the maximum for manufacturing/ground beef exiting packing plants, and were similar. The median and mean ages of manufacturing/ground beef generally increased progressively at the successive stages of distribution, to about 7 and 8 days, respectively, at the times product exited chillers at retail stores (Table 2). The minimum age of product was 2 days or less at all stages of distribution. The maximum ages of manufacturing/ground beef were 18 days or more for product at all stages of distribution except boxing and entering warehouses. At packing plants, 75% of primal cuts were loaded to road trailers within 4 days of the product being boxed (Table 3). The median and maximum temperatures for product in the age range 0–4 days, inclusive, were 3 and
404
C.O. Gill et al. / Meat Science 60 (2002) 401–410
Table 2 The temperatures and ages of boxes of manufacturing/ground beef at six stages of the distribution of beef from packing plants to retail stores Stage of distribution
No. of boxes
Temperature ( C) Median
Mean
Age (days) Min
Max
Median
Mean
Min
Max
Boxing
305
2.3
2.3
2.0
7.2
0
0
0
0
Exit packing plants
300
0.1
1.2
1.8
7.3
1
1.8
0
18
Enter warehouses
492
0.3
0.7
1.7
4.8
2
3.1
0
9
Exit warehouses
437
0.2
0.7
1.4
4.7
6
7.8
1
22
Exit store chillers
293
1.0
1.1
1.1
4.4
7
8.1
2
56
>12 C, respectively. For subsequent, sequential age ranges of 5 days, the median temperatures for cuts stored at packing plants were mostly about 2 C. For boxes of cuts entering warehouses, only 36% were 44 days’ old, while median temperatures for cuts were >1 and < 1 C for product 49 days’ old and 510 days’ old, respectively. For boxes of cuts exiting warehouses, 74% were of ages in the range 5–19 days, inclusive; while the median temperatures for sequential age ranges of 5 days tended to be lower with increasing product age, from 2.1 to 1.2 C. For boxes of cuts entering retail stores, 76% were of ages in the range 5–24 days, inclusive; while median temperatures were >1 and < 1 C for product 414 and 515 days’ old, respectively. For boxes of cuts exiting chillers at retail stores, 70% were of ages in the range 10–24 days, inclusive; while for sequential age ranges of 5 days, median temperatures were mostly >1 C. At packing plants, >90% of boxes of manufacturing/ ground beef were loaded to road trailers within 4 days of the product being boxed (Table 3). For product in the age range 0–4 days, the median temperature was < 0 C, but for the older product loaded from packing plants the median temperature was about 2 C. All boxes of manufacturing/ground beef entering warehouses were < 10 days’ old, with median temperatures < 1 C. For boxes of manufacturing/ground beef exiting warehouses, >70% were 49 days’ old, with median temperatures of 1.5 and 0.3 C for product aged 0–4 and 5– 9 days, respectively. The median temperatures for older product exiting warehouses were < 0 C. For boxes of manufacturing/ground beef entering retail stores, >80% were 49 days’ old, with median temperatures about 2 C. Median temperatures were lower for older product entering retail stores. For boxes of manufacturing/ground beef exiting chillers at retail stores, >70% were 49 days’ old, and < 8% were >14 days’ old. Median temperatures were about 2, about 1 and about 0 C for product aged 0–4, 5–14 and >14 days, respectively.
For boxes of cuts at all stages of distribution except exit from retail store chillers, the median age of product tended to decrease with increasing temperature for sequential, 2 C temperature ranges (Table 4). At all stages of distribution, boxes of cuts of temperatures >6 C were of median ages 0 or 1 day. The fraction of boxes of cuts with temperatures >6 C declined at successive stages of distribution, from about 9% at the times of exiting packing plants, to 0.1% at the times of exiting warehouses. The temperatures of cuts entering retail stores or exiting retail store chillers were all 46 C and of ages 511 days. For boxes of cuts exiting chillers at retail stores, the median age of product increased with increasing temperature for sequential, 2 C temperature ranges. With boxes of manufacturing/ground beef, at each stage of distribution, the median ages of product for sequential, 2 C temperature ranges were generally similar (Table 4). About 3% of boxes of manufacturing/ ground beef exiting packing plants were at temperatures 56 C, but at all other stages of distribution the temperatures of that product were < 6 C. The fractions of product of temperature 40 C were >40% at the times of exiting packing plants and entering or exiting warehouses, but were about 20% at the times of entering retail stores or exiting retail store chillers. At the times of exiting retail store chillers, the temperatures of boxes of manufacturing/ground beef or cuts were similar. For the combined data for all types of product at all stages of distribution, maximum temperatures tended to fall for 10–12 days after product was boxed, but changed little at later times (Fig. 1). Median temperatures fell relatively rapidly for 6–8 days after product was boxed. The median temperatures of product at different packing plants ranged from 5.7–10.7 C, and the maximum temperatures ranged from 9.2 to 18.6 C (Table 5). Minimum temperatures were about or < 0 C at plants which prepared boxed ground beef, but were 52 C at plants which boxed manufacturing but not ground beef. At the times product exited packing plants,
405
C.O. Gill et al. / Meat Science 60 (2002) 401–410
Table 3 The fractions and median temperature of boxes of beef of different age ranges at the time of their being loaded out of packing plants, into or out of refrigerated warehouses, into retail stores, or out of retail store chillers Facilities
Entry or exit
Age range (days)
Cuts Fraction of boxes (%)
Manufacturing/ground Median temperature ( C)
Fraction of boxes (%)
Median temperature ( C)
Packing plants
Exit
0–4 5–9 10–14 15–19 >19
75.6 13.2 7.2 2.4 1.6
3.0 2.1 2.1 0.9 1.9
92.3 2.3 3.3 2.1a
0.1 2.2 1.7 1.9
Warehouses
Entry
0–4 5–9 10–14 15–19 >19
36.2 31.2 23.9 6.9 1.8
2.8 1.5 0.6 0.8 0.7
73.0 27.0
0.4 0.2
Warehouses
Exit
0–4 5–9 10–14 15–19 20–24 25–29 >29
10.0 22.5 26.4 25.0 10.6 3.4 2.1
2.1 1.2 1.3 0.7 0.3 1.0 1.2
31.6 40.0 14.9 6.9 6.6
1.5 0.3 0.5 0.9 0.7
Retail stores
Entry
0–4 5–9 10–14 15–19 20–24 25–29 30–34 >34
6.3 19.2 27.4 19.5 10.6 8.9 3.2 4.9
3.1 1.3 1.3 0.7 0.8 0.6 0.6 0.5
23.9 60.8 9.2 6.1a
7.0 1.8 1.0 0.6
Retail chillers
Exit store
0–4 5–9 10–14 15–19 20–24 25–29 30–34 35–39 40–44 45–49 >49
0.3 6.4 21.5 29.5 19.4 7.2 5.4 2.9 3.4 1.8 2.1
1.4 1.0 0.6 0.9 1.5 1.2 1.2 1.4 1.6 1.0 0.8
12.3 63.8 16.4 7.5a
1.8 0.8 1.1 0.1
a
The fraction includes <1% of product older than 19 days.
the median temperatures of product at all plants were < 4 C. At those times, the median age of product at three plants was 1 day, but at a fourth plant the median age of product was 6 days. At the times product entered warehouses, the median temperatures of product at different warehouses were < 3 C (Table 5). At those times, the median ages of product ranged from 1 to 14 days, but at four of the seven warehouses the median ages of product were 6 or 8 days. At the times product exited warehouses, the median temperatures of product at six warehouses were 42 C and at a seventh warehouse the median temperature was < 3 C. At those times, the median ages of
product were 6 or 8 days at three warehouses, and 510 days at four warehouses. At the times product entered retail stores, the median temperatures of product at different stores ranged from 0 to 4 C, with the median temperatures being < 1 C at nine and >3 C at three of 21 stores (Table 5). At those times the median ages of product were < 10 days at three and >15 days at seven of the stores. At the times product exited the chillers at retail stores, the median temperatures were < 1 C at only three and were >3 C at only one of 21 stores. At those times, the median ages of product were < 10 days at two, 10 or 11 days at three, >15 < 20 days at seven, and 520 days at nine of the stores.
406
C.O. Gill et al. / Meat Science 60 (2002) 401–410
Table 4 The fractions and median ages of boxes of beef of different temperature ranges at the times of their being loaded out of packing plants, into or out of refrigerated warehouses, into retail stores, or out of retail store chillers Facilities
Entry or exit
Temperature range (0 C)
Cuts
Manufacturing/ground
Fraction of boxes (%)
Median age (days)
Fraction of boxes (%)
Median age (days)
Packing plants
Exit
40 0.1–2.0 2.1–4.0 4.1–6.0 6.1–8.0 >8.0
3.4 29.3 43.1 15.5 6.7 2.0
4 3 1 1 0 0
50.0 14.7 18.7 13.3 3.3
1 4 1 1 1
Warehouses
Entry
40 0.1–2.0 2.1–4.0 4.1–6.0 6.1–8.0 >8.0
17.5 38.0 33.9 7.6 1.8 1.2
10 8 3 1 0 1
43.3 38.2 17.7 0.8
2 2 3 3
Warehouses
Exit
40 0.1–2.0 2.1–4.0 4.1–6.0 6.1–8.0
24.2 53.5 20.6 1.6 0.1
16 13 12 2 1
45.8 31.8 21.0 1.4
9 5 5 10
Retail stores
Entry
40 0.1–2.0 2.1–4.0 4.1–6.0
16.5 51.1 26.6 5.8
18 14 13 11
19.2 40.0 30.0 10.8
8 6 5 6
Retail store chillers
Exit
40 0.1–2.0 2.1–4.0 4.1–6.0
20.4 57.3 20.9 1.4
16 18 20 22
20.1 58.0 20.5 1.4
8 7 6 7
About 10% of the product examined at retail stores was branded cuts of median ages 27 or 34 days for product entering stores or exiting store chillers, respectively. For other product at the times of exiting store chillers, about 6% of the product was aged >30 days, and about 2% of the product was aged >40 days. During distribution of boxes of product from one packing plant (P1), the median temperature for product at sequential, 5-day age intervals declined as the age of product increased, to 40 C after 19 days (Table 6). However, for product from a second plant (P2), the median temperatures were < 1 C for the age intervals 5–9 and 10–14 days, but were >1 C at later times; while for product from a third plant (P3), the median temperatures generally remained >1 C. The median temperatures and ages for boxes of beef at the times of their being opened at retail stores were significantly different (P < 0.05) for product from the three packing plants (Table 7). The median temperatures of product were in the order P1 < P2 < P3. Despite that, the warmest product was from plant P1 while the oldest product was from plant P2.
4. Discussion The factors that affect the temperatures of beef during its distribution were not certain when the study was initiated, so the study could not be structured to quantify the effects of factors of known importance. Nor was it possible to examine meat in all distribution processes, or to select product for examination at the later stages of distribution by reference to the packing plants from which it originated. Therefore, the study was designed to obtain only a general description of product temperatures and ages during distribution, with identification of areas where control over product temperature or age might be weak in some processes. When designing the study, it was considered that control over product temperatures might differ substantially between summer and winter months, given the large seasonal changes in temperature in much of Canada. As resources would not allow the replication of the study in winter and summer, data collection was arranged for the summer months on the assumption that product temperatures would then, if they were dif-
407
C.O. Gill et al. / Meat Science 60 (2002) 401–410
Fig. 1. Median temperatures of all (*), the coldest 2% (&) or the warmest 2% (&) of all the product examined in sequential, 2-day age ranges.
Table 5 Ranges of the median, mean, minimum and maximum temperatures and ages of boxed beef at each of several different packing plants, refrigerated warehouses, and retail stores Type of plant
Stage of distribution
No. of plants
No. of boxes at each plant
Total boxes
Temperature (0 C) Median
Mean
Age (days) Min
Max
Median
Mean
Min
Max
Packing plant
Boxing Exit
5 4
88080 900100
4388 3590
8.22.5 2.60.9
8.2 2.5 2.6 1.0
1.23.1 1.21.4
13.9 4.7 8.7 1.6
0 1 or 6
0 4.53.0
0 0 or 1
0 27 10
Warehouse
Entry Exit
7 7
676324 635365
5625 5501
1.81.8 1.01.7
1.9 1.2 1.0 1.6
1.50.6 1.10.9
9.6 3.0 5.9 2.1
76 115
7.15.5 13.26.0
22 33
3824 5329
Retail store
Entry Exit chiller
21 21
130114 9877
1538 2038
2.02.0 1.52.0
1.8 1.8 1.6 1.9
0.41.2 0.22.2
3.9 1.8 4.1 1.6
147 175
13.76.5 20.26.2
54 76
7056 7258
ferent, be higher than at other times. It was further considered that different types of product might have substantially different temperatures or be of different ages, because of both differences in the sizes of product units and differences in the handling and use of various products. However, the data indicated that differences in the temperatures and ages of cuts of different types were small. Although the ages of manufacturing and ground beef were less than those of cuts, the temperatures of manufacturing beef and cuts were generally similar, except that the temperatures of manufacturing beef at packing plants did not range to the higher temperatures of some cuts. The only type of product which
at some times obviously differed in temperature from other products was ground beef. That was to be expected, as meat is commonly cooled during grinding, to temperatures around 0 C, by the addition of carbon dioxide snow to the product in the hoppers that feed grinders (Gill, Rahn, Sloan, & McMullen, 1997). Also, cooling of vacuum packs of ground beef with a cryogen or brine before the product is boxed is becoming a common practice. The temperatures of product from different packing plants were evidently affected by differences in the initial temperatures of product and by differences in the systems through which the product from each plant was
408
C.O. Gill et al. / Meat Science 60 (2002) 401–410
distributed. Despite that, the temperatures and ages of product from all packing plants were similar at the times boxes were opened at retail stores. Therefore, a general description of boxed beef temperatures during distribution of the product in Canada can be made. When beef is packed into boxes at packing plants, its temperature will generally be in the range 2–10 C. Some cuts at most plants will be at temperatures above 10 C, because in carcass cooling processes some carcasses are screened from flows of cold air and so are not cooled effectively (Gill & Bryant, 1997). Although the fractions of warm product will differ between plants, depending on the designs and refrigerative capacities of the carcass cooling facilities, the fraction of warm carcasses cut at most plants seems to be small. However, Canadian regulations require that carcasses be no warmer than 10 C when they are cut (CFIA, 1998a). Moreover, the time required for the warmest product to cool to 7 C, which is the minimum temperature for growth of Escherichia coli, suggest that substantial growth of mesophilic pathogens on the warmest product would be possible (Reichel, Phillips, Jones, & Gill, 1991). There seems to be a need, therefore, for beef packing plants to routinely identify warm carcasses before they are broken, so that such carcasses can be further cooled to temperatures of 10 C or lower. Much of the product prepared at packing plants is loaded to refrigerated road trailers on the day after it is boxed, but some is loaded out of the plant on the day it Table 6 The temperatures, during distribution of product from three packing plants to retail outlets, of boxes of beef of different age ranges Plant
Age (days)
No. of boxes
Temperature (0 C) Median
Mean
Min
Max
P1
0–4 5–9 10–14 15–19 20–24 25–29 >29
2887 1748 1849 1499 526 226 181
2.8 1.3 0.8 0.4 0.0 0.8 0.3
3.3 1.5 0.9 0.5 0.3 0.3 0.1
1.8 2.2 2.1 1.8 1.8 2.0 2.0
9.2 8.6 7.0 4.3 5.5 3.7 5.6
P2
0–4 5–9 10–14 15–19 20–24 25–29 >29
3306 738 850 614 379 95 45
3.3 0.4 0.7 1.3 1.1 1.8 0.7
3.8 0.8 0.9 1.4 1.3 1.7 1.0
2.0 1.8 1.8 1.2 1.7 1.1 1.0
15.9 10.0 5.3 5.0 5.3 4.4 4.1
0–4 5–9 10–14 15–19 20–24 25–29 >29
216 769 364 186 99 19 44
2.7 1.9 1.6 1.0 1.4 0.8 1.1
2.4 1.9 1.6 1.0 1.5 1.2 1.3
1.7 1.6 1.9 1.4 1.6 0.2 1.5
5.0 5.5 5.0 5.7 3.8 3.4 4.0
P3
is boxed. The product may be transported to and unloaded into a refrigerated warehouse within a few hours, or it may remain in a trailer for several days. Wherever the product is located in the days immediately after it is boxed, warm product will apparently cool relatively rapidly, at first. That is to be expected as the few, warmer items will be packed in boxes with cooler product; and boxes containing warm product will be surrounded by boxes of cooler product or be exposed to some flow of cold air. Consequently, by the fourth day after product is boxed, it will mostly be of a temperature < 6 C, irrespective of its temperature at the time of boxing, provided that the box of product is not grossly mishandled. Thus, the practice of storing boxed beef in trailers apparently does not result in warming of the product or even slower cooling than in packing plant or warehouse chillers. However, the similarity of cooling in all three types of facility reflects their common incapacities for rapidly reducing product temperatures, rather than the suitability of refrigerated trailers for receiving product of temperatures that are higher than those desired for storage of the product. Between the 4th and 8th days after packing, the temperatures of some product will apparently decrease. After 8 days, any further, overall declines in the temperatures of product stored at packing plants and warehouses and in transit between such facilities are apparently small. The median temperatures of product are then about 1 C, with temperatures mostly in the range 1–5 C. After product is dispatched from warehouses, the minimum and median temperatures tend to rise to about 0 and 2 C, respectively. However, maximum temperatures are maintained at about 5 C. Those data indicate that the trailers used for transporting beef from warehouses to retail stores, and chillers at retail stores, are generally operated at higher temperatures than both refrigerated warehouses and the trailers used for transporting beef between packing plants and warehouses. The higher temperatures for retail delivery and storage probably reflect the simultaneous carriage and storage at those times of meat and other foods, some of which Table 7 The temperatures and ages of product from three packing plants at the times of boxes of beef being opened at retail storesa Plant No. of Temperature (0 C) Age (days) boxes Median Mean Min Max Median Mean Min Max P1
880
0.7a
0.8
2.0 5.6
16a
16.8
4
56
P2
368
1.6b
1.8
1.0 5.3
19b
18.4
2
44
P3
470
1.0c
1.0
1.9 4.4
12c
15.5
3
131
a
Median values in the same column with different letters are significantly different (P <0.05).
C.O. Gill et al. / Meat Science 60 (2002) 401–410
may deteriorate if exposed to sub-zero temperatures. Apparently, retail chillers and trailers delivering to retail stores are generally operated with off-coil air temperatures of 0 C or more, while at warehouses and in trailers carrying product to warehouses the refrigeration equipment is mostly operated at off-coil air temperatures of 1 C or less. Despite that, air temperatures in box storage chillers at packing plants are apparently mostly above rather than below 0 C. Canadian regulations require that meat be stored and transported at temperatures 44 C (CFIA, 1998b). Moreover, checking of the temperatures of meat when consignments are received, with the rejection of product if temperatures are above 5 C, is an increasingly common commercial practice (Tolstoy, 1991). From the point of view of retail stores, the latter requirement is usually met, as little beef is apparently delivered to such facilities at temperatures above 5 C. However, some commercial customers have sought for boxed beef to be supplied at temperatures consistently about 0 C, while many have occasionally received warm meat. The general inability of commercial customers to obtain beef of temperatures within a narrow, low range, and the occasional delivery of warm meat is commonly ascribed to the inadequate control of temperatures during the transportation of product (James, 1996). Contrary to that view, the data from this survey indicate that consistently low temperatures for product are not achieved, and some product remains persistently warm, largely because it can cool only slowly from the temperatures at the times of packaging, not only in trailers (Scrine, 1985) but in storage facilities as well (Bailey, 1987). Thus, for lower and narrow ranges of temperature to be attained for boxed beef, it will be necessary for box storage chillers at packing plants to be operated in manners which will assure that all product is reduced to chiller temperatures before it is dispatched. For ground beef, the initial temperature trends are the reverse of those for other products, as temperatures tend to rise rather than fall when product is stored at packing plants or retail outlets, although temperatures are likely to be maintained or somewhat reduced during shipment to and storage at warehouses. Because of warming during transport to and storage at retail outlets, the temperatures of ground beef exiting chillers at retail stores are generally similar to those of other product. At most packing plants, the median age of product being loaded to trailers was 1 day. However, the median age for product arriving at some warehouses was 7 days or more. The times required to transport product within Canada would not usually exceed 4 days (Gill & Jones, 1992; Gill, McGinnis, Rahn, & Houde, 1996). Therefore, the lengthy times that some product remains in trailers that are loaded at packing plants reflects delays in dispatching full trailers from packing plants or
409
unloading trailers at warehouses. The former delays probably predominate, as storage facilities at packing plants can usually hold only about 2 days’ production of boxed beef and so some product must often be loaded to trailers before any destinations are decided. That is, trailers are used as ancillary storage facilities as required to deal with fluctuating demands for product. It then appears that much product spends more time in trailers between packing plants and warehouses than it does in the warehouses designed for storing meat. Much beef is aged for a minimum of 14 days before it is delivered to retail stores, to meet with retailers’ specifications which are aimed at assuring an acceptable level of tenderness for the product. Median ages of about the 14 days which were generally found for product delivered to retail stores could then be expected. However, that median figure would be misleading with respect to manufacturing/ground beef, for which the median age at the time of delivery to retail stores was 6 days; and for branded product for which a minimum age of 21 or 28 days at the time of delivery is apparently stipulated. The ages of product at the times of its removal from retail store chillers would also meet with expectations, as a median residence time in those chillers of about 3 days is indicated for most product, but for manufacturing/ground beef the median residence time is only about 1 day. Although the median ages found for product at retail stores were apparently much as might be expected, some product of ages far greater than the median age were observed at each stage of the distribution process. Whatever the reasons for delays in forwarding some small fractions of product, the outcome is apparently that about 5% of product which is intentionally aged for no more than 14 days, if it is intentionally aged at all, is older than 30 days when it is prepared for retail display. The storage life of vacuum-packaged meat decreases rapidly with small increases in temperature within the chiller temperature range (Gill & Molin, 1991). Consideration of the growth rates of spoilage bacteria indicate that product experiencing the median temperatures observed in this study would have a storage life of only about 4 weeks (Gill & Jones, 1992). Thus, half the product stored for longer than 30 days may well be spoiled at the times that vacuum packs are opened. The prolonged storage of boxed beef at the temperatures which are currently obtained for the product would then seem to be economically undesirable. Some improved control of inventories, with the use or freezing of boxed beef a set time after packing would seem to be needed if current ranges of product temperatures persist. The trading of boxed beef within Canada is an established, extensive and successful activity. Therefore, it must be assumed that most beef is stored and transported under conditions that provide product that is
410
C.O. Gill et al. / Meat Science 60 (2002) 401–410
wholly acceptable to commercial customers. Nonetheless, it is apparent that some considerable fraction of product experiences temperatures which are relatively warm for times which would allow the onset of microbial spoilage or, less often, the substantial growth of enteric pathogens. Therefore, the identification and implementation of procedures that would reduce the variabilities of product temperatures and ages, rather than actions to reduce median temperatures and ages, would seem the appropriate approach to addressing the concerns with regards to product safety and storage stability that arise from the current handling of boxed beef during its distribution within Canada.
Acknowledgements The study of boxed beef temperatures was requested by the Quality Starts Here Committee of the Canadian Cattlemen’s Association. Funding for the study was provided by the Canadian Cattlemen’s Association and the Beef Information Centre, and through the Matching Investment Initiative of Agriculture and Agri-Food Canada. Arrangements with packers, warehouse operators and retailers for the collection of data were facilitated by Gilmour Strategies Inc. and Agri-Food Services Inc. The collection of data was carried out with the cooperation and assistance of the managements and staffs of companies and plants across Canada. However, the companies involved with the study wish to remain anonymous. The contributions of all those parties to the study are gratefully acknowledged.
References Bailey, C. (1987). Fundamental problems in the refrigeration of perishable foodstuffs. In Proceedings 17th International Congress of Refrigeration (pp. 203–212). Paris: International Institute of Refrigeration. Bøgh-Sørensen, L., & Olsson, P. (1990). The chill chain. In T. R. Gormley (Ed.), Chilled foods the state of the art (pp. 245–267). London: Elsevier Applied Science.
CFIA (1998a). Refrigeration and related activities. In Meat hygiene manual of procedures (Section 4.10.1). Ottawa: Canadian Food Inspection Agency. CFIA (1998b). Shipment of meat products from registered establishments. In Meat hygiene manual of procedures (Section 8.6). Ottawa: Canadian Food Inspection Agency. Conover, W. J. (1971). Practical nonparametric statistics. New York: Wiley. Farris, D. E., Dietrich, R. A., & Ward, J. B. (1991). Reducing the cost of marketing beef. Meat Processing, February, 60–62. Gill, C. O. (1996). Extending the storage life of raw chilled meats. Meat Science, 43(Supplementary issue ), S99–S109. Gill, C. O., & Bryant, J. (1997). Assessment of the hygienic performances of two beef carcass cooling processes from product temperature history data or enumeration of bacteria on carcass surfaces. Food Microbiology, 14, 593–602. Gill, C. O., & Jones, S. D. M. (1992). Efficiency of a commercial process for the storage and distribution of vacuum-packaged beef. Journal of Food Protection, 55, 880–887. Gill, C. O., & Molin, G. (1991). Modified atmospheres and vacuum packaging. In N. R. Russell, & G. W. Gould (Eds.), Food preservatives (pp. 105–136). Glasgow: Blackie. Gill, C. O., McGinnis, J. C., Rahn, K., & Houde, A. (1996). Control of product temperatures during the storage and transport of bulk containers of manufacturing beef. Food Research International, 29, 647–651. Gill, C. O., Rahn, K., Sloan, K., & McMullen, L. M. (1997). Assessment of the hygienic performances of hamburger patty production processes. International Journal of Food Microbiology, 36, 171–178. James, S. (1996). The chill chain ‘‘from carcass to consumer’’. Meat Science, 43(Supplementary issue), S203–S216. Pearson, A. M. (1994). Introduction to quality attributes and their measurements in meat, poultry and fish products. In A. M. Pearson, & T. R. Dutson (Eds.), Advances in meat research (Vol. 9) (pp. 1– 17). London: Blackie Academic. Reichel, M. P., Phillips, D. M., Jones, R., & Gill, C. O. (1991). Assessment of the hygienic adequacy of a commercial hot boning process for beef by a temperature function integration technique. International Journal of Food Microbiology, 14, 27– 42. Scrine, G. R. (1985). Refrigerated vehicles—what next? In Long distance refrigerated transport: land and sea. Paris: International Institute of Refrigeration. Shapiro, S. S. (1990). How to test normality and other distributional assumptions. Milwaukee: American Society for Quality Control. Tolstoy, A. (1991). Practical monitoring of the chill chain. International Journal of Food Microbiology, 13, 225–230.
Temperatures and ages of boxed beef packed and distributed in Canada C.O. Gilla,*, T. Jonesa, K. Rahnb, S. Campbellb, D.I. LeBlancc, R.A. Holleyd, R. Starke a
Agriculture and Agri-Food Canada Lacombe Research Centre, 6000 C&E Trail, Lacombe, Alberta, Canada T4L 1W1 b Health Canada Laboratory, 110 Stone Road West, Guelph, Ontario, Canada N1G 3W4 c Agriculture and Agri-Food Canada Food Research Centre, Pavillion Jacqueline-Bouchard, University of Moncton, Moncton, New Brunswick, Canada E1A 3E9 d Department of Food Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2 e Agriculture and Agri-Food Canada Kentville Research Centre, 32 Main Street, Kentville, Nova Scotia, Canada B4N 1J5 Received 26 March 2001; received in revised form 18 June 2001; accepted 18 June 2001
Abstract Boxes of beef were examined when product was packed and when boxes were loaded out of five packing plants, when boxes were loaded into and loaded out of seven refrigerated warehouses, and when boxes were received and opened at 21 retail stores. At each stage of handling at each facility, the boxes to be examined were selected at random. For each selected box, the temperature of product at the centre of the box was measured, and the date of packing and the plant of origin were noted. When cuts were packed, the minimum, median and maximum temperatures were about 2, 6 and 18 C, respectively. Temperatures were successively lower when boxes were loaded out of packing plants, into warehouses and out of warehouses. When loaded out of warehouses, the minimum, median and maximum temperatures were about 2, 1 and 8 C, respectively. The ranges of temperatures were similar, but the median temperatures were about 2 or 1.5 C, respectively, when boxes were received at or were opened at retail stores. At packing plants and warehouses, the temperatures of manufacturing and ground beef were lower than those of cuts, but at the retail store the temperatures of all types of product were similar. When boxes were opened at retail stores, the minimum, median and maximum ages of cuts were about 2, 20 and 130 days, respectively; and the corresponding ages for manufacturing and ground beef were 2, 7 and 56 days, respectively. The data indicate that boxed beef is generally cooled to and maintained at temperatures within the range sought by the meat industry. However, cooling to chiller temperatures of product that is packed while warm can take several days; and some product is held for times that are excessive in view of the temperatures of boxed beef. # 2002 Elsevier Science Ltd. All rights reserved. Keywords: Beef; Temperatures; Ages; Distribution
1. Introduction In North America, most beef that will be offered for retail sale is dispatched from packing plants as a chilled, vacuum packed, boxed product. The boxed product is fabricated to retail forms by cutting or grinding, and is packed in retail trays in meat-cutting facilities at retail stores or, increasingly, at central cutting facilities from which it is distributed to retail stores (Farris, Deitrich, & Ward, 1991). Whether the meat is prepared for retail sale in store or centrally, it is likely to be displayed * Corresponding author. Tel.: +1-403-782-8113; fax: +1-403-7826120. E-mail address: [email protected] (C.O. Gill).
within a short time of being fabricated from boxed product (Gill, 1996). Thus, the microbiological condition, appearance and tenderness of the product offered for sale may all be substantially affected by the temperatures experienced by the boxed product and the times for which such product remains in the distribution system (Pearson, 1994). The time for which boxed beef is held, and the temperatures it experiences during distribution can greatly affect the quality of the product. Despite that published data on the temperatures and ages of boxed beef are relatively few, and derive from studies which mostly involved investigations of limited, well defined, distribution systems (Bøgh-Sørensen & Olsson, 1990; Gill & Jones, 1992). No reported survey of the temperatures
0309-1740/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(01)00151-6
402
C.O. Gill et al. / Meat Science 60 (2002) 401–410
and ages of boxed beef identifies the condition of product that is distributed through commercial systems which are sometimes complex. Therefore, to obtain better understanding of the temperatures and ages of boxed beef that is moving through commercial distribution systems, a survey was conducted of the temperatures and ages of boxed beef at production, storage and retail facilities across Canada.
2. Materials and methods 2.1. Ages and temperatures of product The temperatures of product in boxes of beef were determined at various stages of the distribution process. Each selected box of product was opened, and the probe of a thermistor thermometer (TraceableTM; Control Co., Friendswood, TX) was placed between packs of product at the approximate centre of the box. After allowing 2 min for equilibration of the probe, the temperature, to the nearest 0.1 C, was recorded. In addition to the type of product, the date when product was packed and the packing plant number were identified from the information on each box and were recorded. 2.2. Types of product Data were collected from nine types of vacuum packaged primal cuts, which were outside rounds, inside rounds, eyes of rounds, striploins, lip-on ribs, top butts, short cut clods, bone-in blades, and boneless blades. The names given to some of the cuts differed at different packing plants; and similar cuts were prepared in various forms, to conform with customers’ requirements. Differences in names and the exact forms of cuts were disregarded when selecting product for examination. In addition, data were collected from boxes of vacuum packaged trimmings or coarsely ground beef, depending on which of those types of product were available at each facility. 2.3. Collection of data Data were collected during the period June to November 1999, from product at five beef packing plants, seven refrigerated warehouses and 21 retail stores. At beef packing plants, data were collected from product being packed into boxes at the ends of the carcass breaking processes, and from boxes of product being loaded to refrigerated trailers. At refrigerated warehouses, data were collected from product being loaded from trailers into warehouses and from product being loaded into trailers for dispatch from the warehouses. At retail stores, data were collected from product at the times of its delivery to stores and at the times
of boxes being opened for the product to be fabricated to retail-ready items. At each stage of handling at each packing plant or warehouse, data were collected from boxes of product selected at random from those containing product of the selected types, but with no more than 10 boxes of product of one type being selected on any day, and with the examination of a total of no more than 100 boxes of product of one type. At each stage of handling at each retail store, data were collected from boxes of product, selected at random if the number of the available boxes of a type of product exceeded five, with no more than five boxes of product of one type being examined on any day, and with the examination of a total of no more than 25 boxes of product of one type. 2.4. Analysis of data Descriptive statistics for data sets were obtained using Microsoft Excel, version 4, statistical functions (Microsoft Corp, Redmond, WA, USA). Sets of data were tested for normal distribution using the Wilk–Shapiro test (Shapiro, 1990) in the UNIVARIATE procedure of SAS, version 6 (SAS Institute Inc., Cary, NC, USA). Median values for sets of data for product from individual packing plants at the times of boxes being opened at retail stores were separated using the Kruskal–Wallis test (Conover, 1971) in the NPAR1WAY procedure of SAS, version 6 (SAS Institute).
3. Results Most data sets were not normally distributed (P < 0.05), and for most sets the mean was greater than the median. At each stage of the distribution process, for sets of temperatures and ages for each of the nine types of primal cut, seven or more of the median values for temperatures differed by 40.7 C, and seven or more of the median values for ages differed by 43 days (Table 1). The types of cuts that gave values outside those ranges differed at each stage of the distribution process. The variations in mean temperatures and ages were similar, except for the stage of product packing when, at most, only four mean values for the temperatures of cuts of different types differed by 40.7 C. As the data for temperatures and ages of cuts of all types were similar, the data for all cuts were considered together in further analyses. The median and mean temperatures for boxes of primal cuts were lower at each successive stage of distribution from boxing at packing plants to exiting warehouses (Table 1). The median and mean temperatures were higher for primal cuts entering retail stores than for primal cuts exiting warehouses, but the median
403
C.O. Gill et al. / Meat Science 60 (2002) 401–410
Table 1 Ranges of the median, mean, minimum and maximum temperatures and ages of boxes of each of nine types of primal cut at six stages of the distribution of beef from packing plants to retail stores Stages of distribution
No. of boxes of each cut type
Total boxes
Temperature ( C) Median
Mean
Age (days) Min
Max
Median
Mean
Min
Max
0
0
0
0
Boxing
386117
4083
6.60.6
7.2 1.2
2.2 0.5
15.4 3.2
Exit packing plants
31888
3291
2.70.5
3.1 0.7
1.3 1.0
9.6 3.0
2 2
3.92.7
0
2413
Enter warehouses
554104
5115
1.60.5
1.9 0.3
1.8 0.4
10.1 2.5
7 1
7.30.8
0
3922
Exit warehouses
46950
4430
0.80.2
1.1 0.3
1.7 0.3
6.2 1.8
14 2
13.41.9
0 or 1
5131
Enter retail stores
15978
1278
1.50.8
1.6 0.6
1.4 0.4
4.7 1.0
13 3
15.44.0
54
7848
Exit store chillers
395128
1745
1.10.5
1.1 0.4
1.4 0.6
5.0 0.5
21 4
22.16.3
53
8050
and mean temperatures for primal cuts exiting the storage chillers at retail stores were similar to those for primal cuts exiting warehouses. The minimum temperatures for boxes of primal cuts were progressively lower at the successive stages of distribution of boxing, exiting packing plants and entering warehouses, but at later stages the minimum temperatures were similar to those for cuts entering warehouses. The maximum temperatures for boxes of primal cuts were lower for cuts exiting packing plants than for cuts at the times of boxing. The maximum temperatures of primal cuts entering warehouses were similar to the maximum temperatures for cuts exiting packing plants, but maximum temperatures of cuts were progressively lower at the subsequent, successive stages of exiting warehouses and entering retail stores. The maximum temperatures of cuts exiting chillers at retail stores were similar to the maximum temperatures of cuts entering retail stores. At successive stages of the distribution process, the median, mean and maximum ages of boxes of primal cuts increased, and the ranges of the median and mean ages of the different cuts widened (Table 1). At all stages of distribution the oldest cuts were striploins. The minimum age for cuts of all types for the stages of distribution up to and including entering warehouses was 0 days. The minimum age for cuts exiting warehouses was 1 day, except for bone-in blade cuts, for which the minimum age was 0 days. The minimum ages for cuts of different types entering retail stores or exiting retail chillers were mostly between 2 and 6 days. For manufacturing and ground beef, at each stage of the distribution process before delivery to retail stores, the median and mean temperatures were lower than the corresponding temperatures for any type of cut at the same stage of distribution. At all stages of distribution the median and mean ages of manufacturing/ground beef were less than the corresponding ages for any type of cut at the same stage of distribution.
At the times manufacturing or ground beef were placed in boxes, the temperatures of the former product were generally >2 C, while the temperatures of the latter product were < 2 C. The median and mean temperatures for manufacturing/ground beef were lower for product exiting packing plants than for product at the times of boxing (Table 2). Median temperatures were similar for manufacturing/ground beef exiting packing plants, entering warehouses or exiting warehouses, but mean temperatures for product entering or exiting warehouses were less than the mean temperatures for product exiting packing plants. Median and mean temperatures were higher for product entering retail stores than for product exiting warehouses, but median and mean temperatures were less for product exiting chillers at retail stores than for product entering retail stores. The minimum temperature of manufacturing/ ground beef was lowest for product at the times of boxing and highest for product exiting chillers at retail stores. The maximum temperatures for product at the times of boxing and exiting packing plants were similar. The maximum temperatures at the latter stages of distribution were lower than the maximum for manufacturing/ground beef exiting packing plants, and were similar. The median and mean ages of manufacturing/ground beef generally increased progressively at the successive stages of distribution, to about 7 and 8 days, respectively, at the times product exited chillers at retail stores (Table 2). The minimum age of product was 2 days or less at all stages of distribution. The maximum ages of manufacturing/ground beef were 18 days or more for product at all stages of distribution except boxing and entering warehouses. At packing plants, 75% of primal cuts were loaded to road trailers within 4 days of the product being boxed (Table 3). The median and maximum temperatures for product in the age range 0–4 days, inclusive, were 3 and
404
C.O. Gill et al. / Meat Science 60 (2002) 401–410
Table 2 The temperatures and ages of boxes of manufacturing/ground beef at six stages of the distribution of beef from packing plants to retail stores Stage of distribution
No. of boxes
Temperature ( C) Median
Mean
Age (days) Min
Max
Median
Mean
Min
Max
Boxing
305
2.3
2.3
2.0
7.2
0
0
0
0
Exit packing plants
300
0.1
1.2
1.8
7.3
1
1.8
0
18
Enter warehouses
492
0.3
0.7
1.7
4.8
2
3.1
0
9
Exit warehouses
437
0.2
0.7
1.4
4.7
6
7.8
1
22
Exit store chillers
293
1.0
1.1
1.1
4.4
7
8.1
2
56
>12 C, respectively. For subsequent, sequential age ranges of 5 days, the median temperatures for cuts stored at packing plants were mostly about 2 C. For boxes of cuts entering warehouses, only 36% were 44 days’ old, while median temperatures for cuts were >1 and < 1 C for product 49 days’ old and 510 days’ old, respectively. For boxes of cuts exiting warehouses, 74% were of ages in the range 5–19 days, inclusive; while the median temperatures for sequential age ranges of 5 days tended to be lower with increasing product age, from 2.1 to 1.2 C. For boxes of cuts entering retail stores, 76% were of ages in the range 5–24 days, inclusive; while median temperatures were >1 and < 1 C for product 414 and 515 days’ old, respectively. For boxes of cuts exiting chillers at retail stores, 70% were of ages in the range 10–24 days, inclusive; while for sequential age ranges of 5 days, median temperatures were mostly >1 C. At packing plants, >90% of boxes of manufacturing/ ground beef were loaded to road trailers within 4 days of the product being boxed (Table 3). For product in the age range 0–4 days, the median temperature was < 0 C, but for the older product loaded from packing plants the median temperature was about 2 C. All boxes of manufacturing/ground beef entering warehouses were < 10 days’ old, with median temperatures < 1 C. For boxes of manufacturing/ground beef exiting warehouses, >70% were 49 days’ old, with median temperatures of 1.5 and 0.3 C for product aged 0–4 and 5– 9 days, respectively. The median temperatures for older product exiting warehouses were < 0 C. For boxes of manufacturing/ground beef entering retail stores, >80% were 49 days’ old, with median temperatures about 2 C. Median temperatures were lower for older product entering retail stores. For boxes of manufacturing/ground beef exiting chillers at retail stores, >70% were 49 days’ old, and < 8% were >14 days’ old. Median temperatures were about 2, about 1 and about 0 C for product aged 0–4, 5–14 and >14 days, respectively.
For boxes of cuts at all stages of distribution except exit from retail store chillers, the median age of product tended to decrease with increasing temperature for sequential, 2 C temperature ranges (Table 4). At all stages of distribution, boxes of cuts of temperatures >6 C were of median ages 0 or 1 day. The fraction of boxes of cuts with temperatures >6 C declined at successive stages of distribution, from about 9% at the times of exiting packing plants, to 0.1% at the times of exiting warehouses. The temperatures of cuts entering retail stores or exiting retail store chillers were all 46 C and of ages 511 days. For boxes of cuts exiting chillers at retail stores, the median age of product increased with increasing temperature for sequential, 2 C temperature ranges. With boxes of manufacturing/ground beef, at each stage of distribution, the median ages of product for sequential, 2 C temperature ranges were generally similar (Table 4). About 3% of boxes of manufacturing/ ground beef exiting packing plants were at temperatures 56 C, but at all other stages of distribution the temperatures of that product were < 6 C. The fractions of product of temperature 40 C were >40% at the times of exiting packing plants and entering or exiting warehouses, but were about 20% at the times of entering retail stores or exiting retail store chillers. At the times of exiting retail store chillers, the temperatures of boxes of manufacturing/ground beef or cuts were similar. For the combined data for all types of product at all stages of distribution, maximum temperatures tended to fall for 10–12 days after product was boxed, but changed little at later times (Fig. 1). Median temperatures fell relatively rapidly for 6–8 days after product was boxed. The median temperatures of product at different packing plants ranged from 5.7–10.7 C, and the maximum temperatures ranged from 9.2 to 18.6 C (Table 5). Minimum temperatures were about or < 0 C at plants which prepared boxed ground beef, but were 52 C at plants which boxed manufacturing but not ground beef. At the times product exited packing plants,
405
C.O. Gill et al. / Meat Science 60 (2002) 401–410
Table 3 The fractions and median temperature of boxes of beef of different age ranges at the time of their being loaded out of packing plants, into or out of refrigerated warehouses, into retail stores, or out of retail store chillers Facilities
Entry or exit
Age range (days)
Cuts Fraction of boxes (%)
Manufacturing/ground Median temperature ( C)
Fraction of boxes (%)
Median temperature ( C)
Packing plants
Exit
0–4 5–9 10–14 15–19 >19
75.6 13.2 7.2 2.4 1.6
3.0 2.1 2.1 0.9 1.9
92.3 2.3 3.3 2.1a
0.1 2.2 1.7 1.9
Warehouses
Entry
0–4 5–9 10–14 15–19 >19
36.2 31.2 23.9 6.9 1.8
2.8 1.5 0.6 0.8 0.7
73.0 27.0
0.4 0.2
Warehouses
Exit
0–4 5–9 10–14 15–19 20–24 25–29 >29
10.0 22.5 26.4 25.0 10.6 3.4 2.1
2.1 1.2 1.3 0.7 0.3 1.0 1.2
31.6 40.0 14.9 6.9 6.6
1.5 0.3 0.5 0.9 0.7
Retail stores
Entry
0–4 5–9 10–14 15–19 20–24 25–29 30–34 >34
6.3 19.2 27.4 19.5 10.6 8.9 3.2 4.9
3.1 1.3 1.3 0.7 0.8 0.6 0.6 0.5
23.9 60.8 9.2 6.1a
7.0 1.8 1.0 0.6
Retail chillers
Exit store
0–4 5–9 10–14 15–19 20–24 25–29 30–34 35–39 40–44 45–49 >49
0.3 6.4 21.5 29.5 19.4 7.2 5.4 2.9 3.4 1.8 2.1
1.4 1.0 0.6 0.9 1.5 1.2 1.2 1.4 1.6 1.0 0.8
12.3 63.8 16.4 7.5a
1.8 0.8 1.1 0.1
a
The fraction includes <1% of product older than 19 days.
the median temperatures of product at all plants were < 4 C. At those times, the median age of product at three plants was 1 day, but at a fourth plant the median age of product was 6 days. At the times product entered warehouses, the median temperatures of product at different warehouses were < 3 C (Table 5). At those times, the median ages of product ranged from 1 to 14 days, but at four of the seven warehouses the median ages of product were 6 or 8 days. At the times product exited warehouses, the median temperatures of product at six warehouses were 42 C and at a seventh warehouse the median temperature was < 3 C. At those times, the median ages of
product were 6 or 8 days at three warehouses, and 510 days at four warehouses. At the times product entered retail stores, the median temperatures of product at different stores ranged from 0 to 4 C, with the median temperatures being < 1 C at nine and >3 C at three of 21 stores (Table 5). At those times the median ages of product were < 10 days at three and >15 days at seven of the stores. At the times product exited the chillers at retail stores, the median temperatures were < 1 C at only three and were >3 C at only one of 21 stores. At those times, the median ages of product were < 10 days at two, 10 or 11 days at three, >15 < 20 days at seven, and 520 days at nine of the stores.
406
C.O. Gill et al. / Meat Science 60 (2002) 401–410
Table 4 The fractions and median ages of boxes of beef of different temperature ranges at the times of their being loaded out of packing plants, into or out of refrigerated warehouses, into retail stores, or out of retail store chillers Facilities
Entry or exit
Temperature range (0 C)
Cuts
Manufacturing/ground
Fraction of boxes (%)
Median age (days)
Fraction of boxes (%)
Median age (days)
Packing plants
Exit
40 0.1–2.0 2.1–4.0 4.1–6.0 6.1–8.0 >8.0
3.4 29.3 43.1 15.5 6.7 2.0
4 3 1 1 0 0
50.0 14.7 18.7 13.3 3.3
1 4 1 1 1
Warehouses
Entry
40 0.1–2.0 2.1–4.0 4.1–6.0 6.1–8.0 >8.0
17.5 38.0 33.9 7.6 1.8 1.2
10 8 3 1 0 1
43.3 38.2 17.7 0.8
2 2 3 3
Warehouses
Exit
40 0.1–2.0 2.1–4.0 4.1–6.0 6.1–8.0
24.2 53.5 20.6 1.6 0.1
16 13 12 2 1
45.8 31.8 21.0 1.4
9 5 5 10
Retail stores
Entry
40 0.1–2.0 2.1–4.0 4.1–6.0
16.5 51.1 26.6 5.8
18 14 13 11
19.2 40.0 30.0 10.8
8 6 5 6
Retail store chillers
Exit
40 0.1–2.0 2.1–4.0 4.1–6.0
20.4 57.3 20.9 1.4
16 18 20 22
20.1 58.0 20.5 1.4
8 7 6 7
About 10% of the product examined at retail stores was branded cuts of median ages 27 or 34 days for product entering stores or exiting store chillers, respectively. For other product at the times of exiting store chillers, about 6% of the product was aged >30 days, and about 2% of the product was aged >40 days. During distribution of boxes of product from one packing plant (P1), the median temperature for product at sequential, 5-day age intervals declined as the age of product increased, to 40 C after 19 days (Table 6). However, for product from a second plant (P2), the median temperatures were < 1 C for the age intervals 5–9 and 10–14 days, but were >1 C at later times; while for product from a third plant (P3), the median temperatures generally remained >1 C. The median temperatures and ages for boxes of beef at the times of their being opened at retail stores were significantly different (P < 0.05) for product from the three packing plants (Table 7). The median temperatures of product were in the order P1 < P2 < P3. Despite that, the warmest product was from plant P1 while the oldest product was from plant P2.
4. Discussion The factors that affect the temperatures of beef during its distribution were not certain when the study was initiated, so the study could not be structured to quantify the effects of factors of known importance. Nor was it possible to examine meat in all distribution processes, or to select product for examination at the later stages of distribution by reference to the packing plants from which it originated. Therefore, the study was designed to obtain only a general description of product temperatures and ages during distribution, with identification of areas where control over product temperature or age might be weak in some processes. When designing the study, it was considered that control over product temperatures might differ substantially between summer and winter months, given the large seasonal changes in temperature in much of Canada. As resources would not allow the replication of the study in winter and summer, data collection was arranged for the summer months on the assumption that product temperatures would then, if they were dif-
407
C.O. Gill et al. / Meat Science 60 (2002) 401–410
Fig. 1. Median temperatures of all (*), the coldest 2% (&) or the warmest 2% (&) of all the product examined in sequential, 2-day age ranges.
Table 5 Ranges of the median, mean, minimum and maximum temperatures and ages of boxed beef at each of several different packing plants, refrigerated warehouses, and retail stores Type of plant
Stage of distribution
No. of plants
No. of boxes at each plant
Total boxes
Temperature (0 C) Median
Mean
Age (days) Min
Max
Median
Mean
Min
Max
Packing plant
Boxing Exit
5 4
88080 900100
4388 3590
8.22.5 2.60.9
8.2 2.5 2.6 1.0
1.23.1 1.21.4
13.9 4.7 8.7 1.6
0 1 or 6
0 4.53.0
0 0 or 1
0 27 10
Warehouse
Entry Exit
7 7
676324 635365
5625 5501
1.81.8 1.01.7
1.9 1.2 1.0 1.6
1.50.6 1.10.9
9.6 3.0 5.9 2.1
76 115
7.15.5 13.26.0
22 33
3824 5329
Retail store
Entry Exit chiller
21 21
130114 9877
1538 2038
2.02.0 1.52.0
1.8 1.8 1.6 1.9
0.41.2 0.22.2
3.9 1.8 4.1 1.6
147 175
13.76.5 20.26.2
54 76
7056 7258
ferent, be higher than at other times. It was further considered that different types of product might have substantially different temperatures or be of different ages, because of both differences in the sizes of product units and differences in the handling and use of various products. However, the data indicated that differences in the temperatures and ages of cuts of different types were small. Although the ages of manufacturing and ground beef were less than those of cuts, the temperatures of manufacturing beef and cuts were generally similar, except that the temperatures of manufacturing beef at packing plants did not range to the higher temperatures of some cuts. The only type of product which
at some times obviously differed in temperature from other products was ground beef. That was to be expected, as meat is commonly cooled during grinding, to temperatures around 0 C, by the addition of carbon dioxide snow to the product in the hoppers that feed grinders (Gill, Rahn, Sloan, & McMullen, 1997). Also, cooling of vacuum packs of ground beef with a cryogen or brine before the product is boxed is becoming a common practice. The temperatures of product from different packing plants were evidently affected by differences in the initial temperatures of product and by differences in the systems through which the product from each plant was
408
C.O. Gill et al. / Meat Science 60 (2002) 401–410
distributed. Despite that, the temperatures and ages of product from all packing plants were similar at the times boxes were opened at retail stores. Therefore, a general description of boxed beef temperatures during distribution of the product in Canada can be made. When beef is packed into boxes at packing plants, its temperature will generally be in the range 2–10 C. Some cuts at most plants will be at temperatures above 10 C, because in carcass cooling processes some carcasses are screened from flows of cold air and so are not cooled effectively (Gill & Bryant, 1997). Although the fractions of warm product will differ between plants, depending on the designs and refrigerative capacities of the carcass cooling facilities, the fraction of warm carcasses cut at most plants seems to be small. However, Canadian regulations require that carcasses be no warmer than 10 C when they are cut (CFIA, 1998a). Moreover, the time required for the warmest product to cool to 7 C, which is the minimum temperature for growth of Escherichia coli, suggest that substantial growth of mesophilic pathogens on the warmest product would be possible (Reichel, Phillips, Jones, & Gill, 1991). There seems to be a need, therefore, for beef packing plants to routinely identify warm carcasses before they are broken, so that such carcasses can be further cooled to temperatures of 10 C or lower. Much of the product prepared at packing plants is loaded to refrigerated road trailers on the day after it is boxed, but some is loaded out of the plant on the day it Table 6 The temperatures, during distribution of product from three packing plants to retail outlets, of boxes of beef of different age ranges Plant
Age (days)
No. of boxes
Temperature (0 C) Median
Mean
Min
Max
P1
0–4 5–9 10–14 15–19 20–24 25–29 >29
2887 1748 1849 1499 526 226 181
2.8 1.3 0.8 0.4 0.0 0.8 0.3
3.3 1.5 0.9 0.5 0.3 0.3 0.1
1.8 2.2 2.1 1.8 1.8 2.0 2.0
9.2 8.6 7.0 4.3 5.5 3.7 5.6
P2
0–4 5–9 10–14 15–19 20–24 25–29 >29
3306 738 850 614 379 95 45
3.3 0.4 0.7 1.3 1.1 1.8 0.7
3.8 0.8 0.9 1.4 1.3 1.7 1.0
2.0 1.8 1.8 1.2 1.7 1.1 1.0
15.9 10.0 5.3 5.0 5.3 4.4 4.1
0–4 5–9 10–14 15–19 20–24 25–29 >29
216 769 364 186 99 19 44
2.7 1.9 1.6 1.0 1.4 0.8 1.1
2.4 1.9 1.6 1.0 1.5 1.2 1.3
1.7 1.6 1.9 1.4 1.6 0.2 1.5
5.0 5.5 5.0 5.7 3.8 3.4 4.0
P3
is boxed. The product may be transported to and unloaded into a refrigerated warehouse within a few hours, or it may remain in a trailer for several days. Wherever the product is located in the days immediately after it is boxed, warm product will apparently cool relatively rapidly, at first. That is to be expected as the few, warmer items will be packed in boxes with cooler product; and boxes containing warm product will be surrounded by boxes of cooler product or be exposed to some flow of cold air. Consequently, by the fourth day after product is boxed, it will mostly be of a temperature < 6 C, irrespective of its temperature at the time of boxing, provided that the box of product is not grossly mishandled. Thus, the practice of storing boxed beef in trailers apparently does not result in warming of the product or even slower cooling than in packing plant or warehouse chillers. However, the similarity of cooling in all three types of facility reflects their common incapacities for rapidly reducing product temperatures, rather than the suitability of refrigerated trailers for receiving product of temperatures that are higher than those desired for storage of the product. Between the 4th and 8th days after packing, the temperatures of some product will apparently decrease. After 8 days, any further, overall declines in the temperatures of product stored at packing plants and warehouses and in transit between such facilities are apparently small. The median temperatures of product are then about 1 C, with temperatures mostly in the range 1–5 C. After product is dispatched from warehouses, the minimum and median temperatures tend to rise to about 0 and 2 C, respectively. However, maximum temperatures are maintained at about 5 C. Those data indicate that the trailers used for transporting beef from warehouses to retail stores, and chillers at retail stores, are generally operated at higher temperatures than both refrigerated warehouses and the trailers used for transporting beef between packing plants and warehouses. The higher temperatures for retail delivery and storage probably reflect the simultaneous carriage and storage at those times of meat and other foods, some of which Table 7 The temperatures and ages of product from three packing plants at the times of boxes of beef being opened at retail storesa Plant No. of Temperature (0 C) Age (days) boxes Median Mean Min Max Median Mean Min Max P1
880
0.7a
0.8
2.0 5.6
16a
16.8
4
56
P2
368
1.6b
1.8
1.0 5.3
19b
18.4
2
44
P3
470
1.0c
1.0
1.9 4.4
12c
15.5
3
131
a
Median values in the same column with different letters are significantly different (P <0.05).
C.O. Gill et al. / Meat Science 60 (2002) 401–410
may deteriorate if exposed to sub-zero temperatures. Apparently, retail chillers and trailers delivering to retail stores are generally operated with off-coil air temperatures of 0 C or more, while at warehouses and in trailers carrying product to warehouses the refrigeration equipment is mostly operated at off-coil air temperatures of 1 C or less. Despite that, air temperatures in box storage chillers at packing plants are apparently mostly above rather than below 0 C. Canadian regulations require that meat be stored and transported at temperatures 44 C (CFIA, 1998b). Moreover, checking of the temperatures of meat when consignments are received, with the rejection of product if temperatures are above 5 C, is an increasingly common commercial practice (Tolstoy, 1991). From the point of view of retail stores, the latter requirement is usually met, as little beef is apparently delivered to such facilities at temperatures above 5 C. However, some commercial customers have sought for boxed beef to be supplied at temperatures consistently about 0 C, while many have occasionally received warm meat. The general inability of commercial customers to obtain beef of temperatures within a narrow, low range, and the occasional delivery of warm meat is commonly ascribed to the inadequate control of temperatures during the transportation of product (James, 1996). Contrary to that view, the data from this survey indicate that consistently low temperatures for product are not achieved, and some product remains persistently warm, largely because it can cool only slowly from the temperatures at the times of packaging, not only in trailers (Scrine, 1985) but in storage facilities as well (Bailey, 1987). Thus, for lower and narrow ranges of temperature to be attained for boxed beef, it will be necessary for box storage chillers at packing plants to be operated in manners which will assure that all product is reduced to chiller temperatures before it is dispatched. For ground beef, the initial temperature trends are the reverse of those for other products, as temperatures tend to rise rather than fall when product is stored at packing plants or retail outlets, although temperatures are likely to be maintained or somewhat reduced during shipment to and storage at warehouses. Because of warming during transport to and storage at retail outlets, the temperatures of ground beef exiting chillers at retail stores are generally similar to those of other product. At most packing plants, the median age of product being loaded to trailers was 1 day. However, the median age for product arriving at some warehouses was 7 days or more. The times required to transport product within Canada would not usually exceed 4 days (Gill & Jones, 1992; Gill, McGinnis, Rahn, & Houde, 1996). Therefore, the lengthy times that some product remains in trailers that are loaded at packing plants reflects delays in dispatching full trailers from packing plants or
409
unloading trailers at warehouses. The former delays probably predominate, as storage facilities at packing plants can usually hold only about 2 days’ production of boxed beef and so some product must often be loaded to trailers before any destinations are decided. That is, trailers are used as ancillary storage facilities as required to deal with fluctuating demands for product. It then appears that much product spends more time in trailers between packing plants and warehouses than it does in the warehouses designed for storing meat. Much beef is aged for a minimum of 14 days before it is delivered to retail stores, to meet with retailers’ specifications which are aimed at assuring an acceptable level of tenderness for the product. Median ages of about the 14 days which were generally found for product delivered to retail stores could then be expected. However, that median figure would be misleading with respect to manufacturing/ground beef, for which the median age at the time of delivery to retail stores was 6 days; and for branded product for which a minimum age of 21 or 28 days at the time of delivery is apparently stipulated. The ages of product at the times of its removal from retail store chillers would also meet with expectations, as a median residence time in those chillers of about 3 days is indicated for most product, but for manufacturing/ground beef the median residence time is only about 1 day. Although the median ages found for product at retail stores were apparently much as might be expected, some product of ages far greater than the median age were observed at each stage of the distribution process. Whatever the reasons for delays in forwarding some small fractions of product, the outcome is apparently that about 5% of product which is intentionally aged for no more than 14 days, if it is intentionally aged at all, is older than 30 days when it is prepared for retail display. The storage life of vacuum-packaged meat decreases rapidly with small increases in temperature within the chiller temperature range (Gill & Molin, 1991). Consideration of the growth rates of spoilage bacteria indicate that product experiencing the median temperatures observed in this study would have a storage life of only about 4 weeks (Gill & Jones, 1992). Thus, half the product stored for longer than 30 days may well be spoiled at the times that vacuum packs are opened. The prolonged storage of boxed beef at the temperatures which are currently obtained for the product would then seem to be economically undesirable. Some improved control of inventories, with the use or freezing of boxed beef a set time after packing would seem to be needed if current ranges of product temperatures persist. The trading of boxed beef within Canada is an established, extensive and successful activity. Therefore, it must be assumed that most beef is stored and transported under conditions that provide product that is
410
C.O. Gill et al. / Meat Science 60 (2002) 401–410
wholly acceptable to commercial customers. Nonetheless, it is apparent that some considerable fraction of product experiences temperatures which are relatively warm for times which would allow the onset of microbial spoilage or, less often, the substantial growth of enteric pathogens. Therefore, the identification and implementation of procedures that would reduce the variabilities of product temperatures and ages, rather than actions to reduce median temperatures and ages, would seem the appropriate approach to addressing the concerns with regards to product safety and storage stability that arise from the current handling of boxed beef during its distribution within Canada.
Acknowledgements The study of boxed beef temperatures was requested by the Quality Starts Here Committee of the Canadian Cattlemen’s Association. Funding for the study was provided by the Canadian Cattlemen’s Association and the Beef Information Centre, and through the Matching Investment Initiative of Agriculture and Agri-Food Canada. Arrangements with packers, warehouse operators and retailers for the collection of data were facilitated by Gilmour Strategies Inc. and Agri-Food Services Inc. The collection of data was carried out with the cooperation and assistance of the managements and staffs of companies and plants across Canada. However, the companies involved with the study wish to remain anonymous. The contributions of all those parties to the study are gratefully acknowledged.
References Bailey, C. (1987). Fundamental problems in the refrigeration of perishable foodstuffs. In Proceedings 17th International Congress of Refrigeration (pp. 203–212). Paris: International Institute of Refrigeration. Bøgh-Sørensen, L., & Olsson, P. (1990). The chill chain. In T. R. Gormley (Ed.), Chilled foods the state of the art (pp. 245–267). London: Elsevier Applied Science.
CFIA (1998a). Refrigeration and related activities. In Meat hygiene manual of procedures (Section 4.10.1). Ottawa: Canadian Food Inspection Agency. CFIA (1998b). Shipment of meat products from registered establishments. In Meat hygiene manual of procedures (Section 8.6). Ottawa: Canadian Food Inspection Agency. Conover, W. J. (1971). Practical nonparametric statistics. New York: Wiley. Farris, D. E., Dietrich, R. A., & Ward, J. B. (1991). Reducing the cost of marketing beef. Meat Processing, February, 60–62. Gill, C. O. (1996). Extending the storage life of raw chilled meats. Meat Science, 43(Supplementary issue ), S99–S109. Gill, C. O., & Bryant, J. (1997). Assessment of the hygienic performances of two beef carcass cooling processes from product temperature history data or enumeration of bacteria on carcass surfaces. Food Microbiology, 14, 593–602. Gill, C. O., & Jones, S. D. M. (1992). Efficiency of a commercial process for the storage and distribution of vacuum-packaged beef. Journal of Food Protection, 55, 880–887. Gill, C. O., & Molin, G. (1991). Modified atmospheres and vacuum packaging. In N. R. Russell, & G. W. Gould (Eds.), Food preservatives (pp. 105–136). Glasgow: Blackie. Gill, C. O., McGinnis, J. C., Rahn, K., & Houde, A. (1996). Control of product temperatures during the storage and transport of bulk containers of manufacturing beef. Food Research International, 29, 647–651. Gill, C. O., Rahn, K., Sloan, K., & McMullen, L. M. (1997). Assessment of the hygienic performances of hamburger patty production processes. International Journal of Food Microbiology, 36, 171–178. James, S. (1996). The chill chain ‘‘from carcass to consumer’’. Meat Science, 43(Supplementary issue), S203–S216. Pearson, A. M. (1994). Introduction to quality attributes and their measurements in meat, poultry and fish products. In A. M. Pearson, & T. R. Dutson (Eds.), Advances in meat research (Vol. 9) (pp. 1– 17). London: Blackie Academic. Reichel, M. P., Phillips, D. M., Jones, R., & Gill, C. O. (1991). Assessment of the hygienic adequacy of a commercial hot boning process for beef by a temperature function integration technique. International Journal of Food Microbiology, 14, 27– 42. Scrine, G. R. (1985). Refrigerated vehicles—what next? In Long distance refrigerated transport: land and sea. Paris: International Institute of Refrigeration. Shapiro, S. S. (1990). How to test normality and other distributional assumptions. Milwaukee: American Society for Quality Control. Tolstoy, A. (1991). Practical monitoring of the chill chain. International Journal of Food Microbiology, 13, 225–230.