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Consumer acceptance of display packs of beef stored under N2 or CO2 in master packs
Meat Science 38 (1994) 397-406
© 1994 Elsevier Science Limited Printed in Great Britain. All rights reserved 0309-1740/94/$07.00 ELSEVIER
Consumer Acceptance of Display Packs of Beef Stored under N2 or CO2 in Master Packs C. O. Gill, C. McGinnis & A. K. W. Tong Agriculture Canada Research Station, Bag Service 5000, Lacombe, Alberta, T0C 1S0, Canada (Received 21 June 1993; revised version received 22 October 1993; accepted 26 October 1993)
ABSTRACT Display-packaged samples of beefsteak and of ground beef were delivered to the homes of 120 panelists. Each panelist received a set of samples of each meat. Each set consisted of one sample freshly prepared for retail display from vacuum-packaged product, one retail-packaged and then stored in a master pack under N2 and one retail-packaged and then stored under CO 2. The samples in each set were prepared from the same strip loin or batch of coarsely ground beef and had been stored for between 21 and 23 days ai 2°C. The panelists completed questionnaires on the attributes of the meats while they were packaged, when they were unpackaged for cooking, and when they were eaten. The responses to each question were tabulated, and the probability of the X2 statistics was calculated for each table. There were no significant differences in the general acceptability of the steaks from the three storage treatments. Significant numbers of panelists judged that ground beef prepared from vacuum-packaged product was of better eolour and had less exudate, but was of poorer eating quality than the product from master packs. However, the majority of panelists did not distinguish between ground beef from the three storage treatments. The consumer responses indicate that controlled-atmosphere master packaging of display packs may offer a means of preserving display-ready beef for times that would allow wide distribution of the product through current commercial systems. INTRODUCTION The preparation of retail packs of meat at central facilities can have considerable economic benefits (Farris et al., 1991). However, the distribution of product prepared in current central-cutting operations is severely restricted by the limited 397
398
C. O. Gill, C. McGinnis, A. K. W. Tong
stability of meat packaged in conventional or high-oxygen modified-atmosphere display packs. A recent study of beef distribution, from a N o r t h American packing plant to a relatively close retail outlet, indicated that a storage life approaching 3 weeks is required for beef to be conveniently marketed. Such a lengthy period is needed because product must be stockpiled at both the wholesale and retail levels, to cope effectively with the fluctuating demands of customers (Gill & McGinnis, 1993). Under simulated commercial conditions, display-packaged ground beef and beef steaks achieved a storage life of 3 weeks or longer when they were master-packaged under oxygen-depleted atmospheres of N2 or CO2. After the master packs were opened, the product had a display life similar to that of vacuum-packaged product that was stored for the same time and ground, or cut into steaks, immediately before it was displayed (Gill & Jones, 1994a, b). Master packaging of retail-packaged product under oxygen-depleted atmospheres could then offer a general means o f preserving chilled beef during its distribution from central-cutting facilities. However, some indication of consumer reactions to product from such master packagings is required before commercial application of the technique can be considered. A study was therefore conducted to determine whether consumers were likely to discriminate against beef in retail packs that were stored for 3 weeks under oxygen-depleted atmospheres.
MATERIALS AND METHODS A consumer panel of 120 people was recruited to obtain a panel distributed with regard to sex, age, and family composition in proportions that approximate to those of the population o f Canada (Table 1). Names were selected at random from a local telephone directory. Persons were called in the order of selection of their names. Respondents who indicated a willingness to participate, and whose sex, age, and family circumstances corresponded with a vacant position in the panel, were recruited. Vacuum-packaged strip loins were obtained from a beef plant on the day after each animal was slaughtered. The loins were stored overnight at 2°C. Each loin was then divided into three portions. One portion was vacuum-packaged in a film that has an O2-transmission rate o f 40 cm 3 O2/m2/24h/atm at 25°C and 100% r.h. (Barrier film; Cryovac, Mississauga, ON, Canada). The other two portions TABLE 1 The Composition of the Consumer Panel that Evaluated Beef Samples Group
Men without resident family (19-60) Women without resident family (19-60) Men over 60 ~with or without Women over 60 /resident spouse Families with a child <10 Families with a child/children >10, or no children
Number
10 10 16 20 31 33
Acceptanceof master-packedbeef
399
were each divided into three steaks. Each steak was placed on a solid polystyrene tray with walls 25 mm high. Each filled tray was placed in a pouch of a shrinkable film that has antifogging properties and an O2-transmission rate of 11 000 cm3/ mZ/24h/atm at 25°C and 75% r.h. (RD 106; Cryovac). After being sealed, the pouch was shrunk to the tray by using a hot-air gun. A 3 mm hole made in the film at one corner of the tray allowed the film to form as a flat lid to the tray. The six display packs prepared from each loin were divided into two groups, and each group of three packs was master-packed in a pouch composed of a gas-impermeable aluminum-foil laminate (American National Can Co., Meenak, WI, USA). One pouch was filled with 3 litres of Nz and one with 3 litres of CO2 by using a packaging machine (Captron III; RMF, Grandview, MO, USA) that gives a pack atmosphere of either gas with a residual 02 concentration of <500 ppm. The loin origin of the contained product was identified on each vacuum and master pack. All the vacuum and master packs were stored at 2°C for between 21 and 23 days. Similarly, vacuum packs of beef trimmings were obtained from a beef plant on days in which the trimmings were packaged. Each 10 kg batch of trimmings was coarsely ground and then divided into three equal portions. One portion was vacuum-packaged. The other two portions were finely ground and then distributed into trays. Each tray contained 420 +20 g of ground beef, with the meat surface 5 mm below the top of the tray walls. Each tray was packaged in the film of high oxygen-permeability, and the display packs were master-packaged and stored as for the steaks. When product was to be distributed, the master packs and vacuum packs containing product from the same loin, or from the same batch of ground beef, were withdrawn. The master packs were opened, and the product was held in air at -1.5°C for 2 h to allow the meat to bloom. Display packs of steak or finely ground beef were prepared from the vacuum-packaged product. The samples were then distributed to panelists over a period of between 2 and 5 h. Each panelist received three steaks from the same loin, each steak having been subjected to a different storage treament, and three packs of ground beef from the same batch, each pack having been subjected to a different storage treatment. On delivery of the samples, the accompanying questionnaires (Table 2) were explained to each panelist. The questions on the fat perceived at each stage of each assessment were included as a control on the responses. In addition to answering the questions posed, the panelists were asked to record any comment they thought appropriate at each stage of the assessment. After the explanation of the requirements, the portions of the questionnaires that dealt with the appearance of the display-packaged meats were completed by the panelists. The panelists were asked not to freeze the steaks but to consume them within 3 days. They were also asked to store and prepare the ground meat as they would do for purchased product and to consume the ground meat within 14 days. After that time, the completed questionnaire was recovered from each panelist. The frequencies of the responses to each question were tabulated for each type of storage packaging. The probability of xZ-test statistic was calculated for each table according to the SAS (1990) frequency procedure. Tables for which the probability was <0.05 were considered to show dependence of the response frequency on the storage treatment. Such tables were examined to determine the differences in the response frequencies between the three storage treatments.
400
C. O. Gill, C McGinnis, A. K. IV. Tong
TABLE 2
The Questions and Possible Responses Contained in the Questionnaires on DisplayPackaged Beef Steaks and Ground Beef Product state preparation Packaged
Storage
Unpackaged
Preparation
Cooked
Question
Responses
General acceptability
very good, good, fair, neither poor nor good, poor, very poor
Exudate
too wet, about right, too dry
Colour
much too dark, too dark, just right, too light, much too light
Fat content
much too fatty, too fatty, just right, too lean, much too lean
Frozen or not frozen a
frozen, not frozen
Thawing method (if frozen) a
room, refrigerator, microwave
General acceptability
very good, good, fair, neither poor nor good, poor, very poor
Odour
very pleasant, pleasant, acceptable, unpleasant, very unpleasant
Exudate
too wet, about right, too dry
Colour
much too dark, too dark, just right, too light, much too light
Fat content
much too fatty, too fatty, just right, too lean, much too lean
Cooking method
grilled, fried, baked, boiled
Degree of cooking (if grilled or fried)
blue, rare, medium rare, well-done
General acceptability
very good, good, fair, poor, very poor
Odour b
very pleasant, pleasant, acceptable, unpleasant, very unpleasant very tender, tender, not tender enough, tough
Tenderness b Flavour b
very pleasant, pleasant, acceptable, unpleasant, very unpleasant
Fat content b
much too fatty, too fatty, just right, too lean, much too lean
a Questions asked for ground beef only. b Questions asked for steaks only.
Acceptanceof master-packedbeef
401
RESULTS Responses to the questions on fat content The fat content of the three samples of meat in any set were similar, so perceptions of different fat contents in the three samples could arise only from some biasing effect of the packaging treatments. In the event, the perceptions of differences in fat content by a few panelists were not significant. Responses to steaks With steaks, there were no significant differences in the response frequencies for the three storage treatments in the responses to the questions on the general acceptability of the meat when packaged, unpackaged, or cooked (Fig. 1). Despite that, there were significant (P<0.05) differences in the response frequencies to the question on the colour of the packaged meat and to the question concerning exudate in the unpackaged meat. The significant differences in response to the question on colour arose, despite >90% of the panelists scoring all steak colours as 'just right' because of a relatively high frequency (6%) of 'too dark' scores for steaks stored under Nz and of 'too light' scores for steaks stored under CO2. The significant differences in response to the question on exudate arose because steaks from the vacuum, N2, and CO2 storage treatments were, respectively considered 'too wet' by 6, 12 and 11% of panelists, and 'too dry' by 7, 0 and 6%. Responses to ground beef For packaged ground beef, the differences in the response frequencies for the three storage treatments were significant (P < 0-05) for the questions on general impression and colour, highly significant (P< 0-001) for the question on exudate, and not significant only for the question on fat content. Evidently, more of the product from vacuum than from master packs gave a 'very good' general impression, because product stored under N 2 w a s more frequently considered 'too dark', whereas product stored under CO2 was more frequently considered 'too wet' (Fig. 2). For unpackaged ground beef, there were no significant differences in the sets of responses to any question except that concerned with exudate. For the latter characteristic, a significant (P<0.05) number of panelists perceived that the product stored in vacuum pack had less exudate than the product stored under N2 or CO2, with the vacuum-packaged product being more frequently considered 'too dry' (Fig. 3). In response to the single question on cooked ground meat, a significant (P < 0.05) number of panelists perceived that the product stored in vacuum pack was of poorer quality than the product stored under N2 or CO2 (Fig. 4). Storage and preparation of the meats by panelists The steaks were grilled by 71% of the panelists and fried by 28%. The ground beef was frozen by 84% of the panelists. Of those who froze the meat, 54, 28, and 18% thawed the meat at room temperature, in a refrigerator, or by micro-
402
C. O. Gill, C. McGinnis, A. K: W. Tong Storage Treatment Vacuum
N 2 atmosphere
CO 2 atmosphere
100 packaged
packaged
packaged
50
a
o~ >., ¢J t.¢,
O"
O) c O O. gl
100
b
c
d
e
unpackaged
a
b
c
d
e
unpackaged
a
b
e
d
e
unpackaged
so
0 a
b
c
d
e
a
b
c
d
e
a
b
c
d
e
100
cooked
cooked
cooked
50
a
b
c
d
e
a
b
c
d
e
a
b
c
d
e
responses Fig. 1. The frequencies of responses to questions on the general acceptability of packaged, unpackaged, and cooked steaks. The responses were: a = very good, b = good, c = fair, d = neither poor nor good, e = poor. wave heating, respectively. The g r o u n d beef was grilled or fried by 60% o f the panelists, with the m e a t otherwise being c o o k e d in a variety o f boiled or b a k e d dishes. Panelists' comments
O f the panelists, 49 recorded c o m m e n t s on the steaks. O f these, 28 were wholly c o m p l i m e n t a r y a b o u t the m e a t f r o m all storage packagings. Only one or two panelists c o m m e n t e d adversely on the colour, odour, or tenderness o f meat, a n d
Acceptance of master-packed beef
403
Stora,qe treatment Vacuum
100
N ~ atmosphere
general impression
general impression
CO 2 atmosphere
general impression
50 -a b c d e o~ v
100
colour
a
b
c
d
e
colour
a b c d e colour
t~ c
o
50
o
t.o Q, ca
0
fl L f g h i l
f gh i l
f g h
i
j
100
exuda~
exudatec~
exudat~
50
k
I
m
k
I
m
k
I
m
responses Fig. 2. The frequencies of responses to questions on the general acceptability and colour of, and the perception of exudate in, ground beef in display packs. The responses were: general impression, a -- very good, b -- good, c --- fair, d = neither good nor poor, e = poor; colour, f = much too dark, g = too dark, h = just right, i = too light, j = much too light; exudate, k = too wet, 1 -- about right, m= too dry. all such c o m m e n t s were a p p l i e d to the m e a t f r o m all three s t o r a g e p a c k a g i n g s . A d v e r s e c o m m e n t s o n e x u d a t e were m a d e with r e g a r d to m e a t s t o r e d u n d e r v a c u u m , N2, o r COz b y two, six, a n d six panelists, respectively. A d v e r s e c o m m e n t s o n f l a v o u r were m a d e w i t h r e g a r d to m e a t s t o r e d u n d e r v a c u u m , N2, o r CO2 b y two, t w o a n d five panelists, respectively. N i n e t e e n o f the panelists c o m m e n t e d o n the p a c k a g i n g . O f their c o m m e n t s , twelve were f a v o u r a b l e a n d o n e was u n f a v o u r a b l e , while 6 were c o n c e r n e d with w h e t h e r o r n o t the p a c k a g i n g c o u l d be recycled.
404
C. O. Gill, C. McGinn&, A. K. W.. Tong
Storage treatment Vacuum v
>~
N;; a t m o s p h e r e
COz atmosphere
100
E 0
Z3-
50 (I) tO O~
0 a
b
h c
a
b
c
a
b
c
responses
Fig. 3. The frequencies of responses to a question on the perception of exudate in ground beef that had been removed from display packs. The responses were: a = too wet, b = about right, c -- too dry. Some 52 panelists recorded comments on the ground beef. Of these, 23 were wholly complimentary about the meat from all storage packagings. The colour of meat from all storage packagings was commented on favourably by seven panelists. Six panelists commented on the colour of thawed meat from all storage packagings, three favourably and three unfavourably. Adverse comments on exudate were made with regard to meat stored under vacuum, N2, or CO2 by two, five, and five panelists, respectively. Adverse comments on the odour of cooked meat that had been stored under vacuum, N2, or CO2 were made by eight, one, and one panelists, respectively. Of eight comments on the
Storage treatment N;I atmosphere
Vacuum
CO = atmosphere
100 r"
so eo e~
Itl
•
0
abcd
e f
a b c d e f
abc
de
f
responses
The frequencies of responses to a question on the general acceptability of cooked ground beef. The responses were: a = very good, b = g o o d , c = f a i r , d = neither poor not good, e = poor, f = very poor. Fig. 4.
Acceptance of master-packedbeef
405
packaging, five were favourable, one was unfavourable, and two were concerned with recycling. DISCUSSION In the region where the trial was conducted, fresh meat is almost invariably retailed in a traditional (tray and overwrap) packaging. The display packaging used for the trial was necessarily constructed of commercially available trays and films. Because of this limitation, it was not possible to construct an overwrapped tray from which air could be reliably exhausted during the evacuation of master packs. Consequently, panelists were presented with meat in an unfamiliar, lidded type of tray. The panelists' comments suggest that any biasing of responses by the unfamiliar packaging would be favourable rather than otherwise. The questions on unpackaged ground beef did not include one on general acceptability. It seemed likely that the samples of ground beef in any set could be subjected to different storage and/or preparation treatments within some homes. Responses to a general question might then sometimes be founded on misleading recollections of the samples first unpackaged. It was considered that any such effect might be reduced by asking only specific questions. In contrast, comparison of specific eating qualities seemed inappropriate when the meat from different samples could be prepared in different ways at different times. Hence only one general question was asked on the eating quality of ground beef, with the intention of considering consumer comments for an explanation of any indication that a storage packaging had produced a particular effect. With packaged steaks, a small minority of panelists distinguished some colour differences between meat that had been stored under vacuum, N2, or CO2. However, these distinctions did not result in any significant differences in the ratings of general acceptability. Moreover, no adverse comment was made on colour by any panelist. It therefore seems that, if the storage packaging does affect the meat colour, the effect will be too small to be of any real consequence to consumers. It would be expected that steaks stored in a master package would lose more exudate than freshly cut steaks (Offer & Knight, 1988). The perception of excessive exudate when steaks were unpackaged in more of the master-packaged than the freshly cut steaks could then be expected. However, excessive free exudate in packs could be prevented by the use of an absorbent of adequate capacity. Such a simple adjustment of the packaging would seemingly eliminate any significant differences between steaks from the three storage packagings. A large fraction of panelists perceived that ground beef from master packs was darker, and had more exudate, than the product that was finely ground after being stored in a vacuum pack. The colour difference seemingly arose, at least in part, from the storage of coarsely ground meat in vacuum packs. This resulted in the fat's being stained by exudate. The pale pink fat in the finely ground product tended to lighten the perceived red colour of the mass. In contrast, the fat in the master.packaged product remained white, so the red colour perceived was that of the muscle tissue alone. The colour differences would then seem to have been due to the vacuum-packaged product appearing lighter red, rather than the master-packaged product appearing dark, than would freshly ground-beef trimmings.
406
C. O. Gill, C. McGinnis, A. K. W. Tong
As with the steaks, more exudate would be expected in the master-packaged ground beef than in that freshly prepared from vacuum-packaged product. Again, consumer perception of excessive exudate could be avoided by the use of a suitable absorbent. A significant number of panelists considered the ground meat prepared from vacuum-packaged product to have been of poorer eating quality than the product from master packs. The comments of some panelists indicate that their adverse response to the former was occasioned by their perceptions of off-flavours. It is possible that flavour deterioration in the coarsely ground, vacuum-packed product was related to the ingress of small quantities of oxygen through the packaging film (Jeremiah et al., 1992), while no such deterioration could occur in the product master-packed in a gas-impermeable film. The results of this study clearly suggest that consumers would find retail packs of beef from master packs with oxygen-depleted atmospheres as acceptable as product stored in vacuum pack and prepared for display only on the day of intended sale. Master packaging under oxygen-depleted atmospheres could then be a commercially useful means of preserving retail-ready beef during times adequate for the wide distribution of product from a central-cutting location. ACKNOWLEDGMENTS We thank Dr L. E. Jeremiah for his advice on consumer-testing procedures, and the Alberta Cattle Commission for its financial support of this study. REFERENCES Farris, D. E., Dietrich, R. A. & Ward, J. B. (1991). Meat Process. 30 (2), 60. Gill, C. O. & Jones, T. (1994a). Meat Sci., 37, 281. Gill, C. O. & Jones, T. (1994b). Meat Sci.., 38, 385. Gill, C. O. & McGinnis, C. (1993). Int. J. Food Microbiol., 18, 321. Jeremiah, L. E., Gill, C. O. & Penney, N. (1992). J. Muscle Foods, 3, 263. Offer, G. I. & Knight, P. (1988). In Developments in Meat Science, Vol. 4, ed. R. Lawrie. Elsevier Applied Science, London, p. 173. SAS (1990). SAS/STAT User's Guide, Version 6, 4th Ed. SAS Institute, Cary, NC, USA.
© 1994 Elsevier Science Limited Printed in Great Britain. All rights reserved 0309-1740/94/$07.00 ELSEVIER
Consumer Acceptance of Display Packs of Beef Stored under N2 or CO2 in Master Packs C. O. Gill, C. McGinnis & A. K. W. Tong Agriculture Canada Research Station, Bag Service 5000, Lacombe, Alberta, T0C 1S0, Canada (Received 21 June 1993; revised version received 22 October 1993; accepted 26 October 1993)
ABSTRACT Display-packaged samples of beefsteak and of ground beef were delivered to the homes of 120 panelists. Each panelist received a set of samples of each meat. Each set consisted of one sample freshly prepared for retail display from vacuum-packaged product, one retail-packaged and then stored in a master pack under N2 and one retail-packaged and then stored under CO 2. The samples in each set were prepared from the same strip loin or batch of coarsely ground beef and had been stored for between 21 and 23 days ai 2°C. The panelists completed questionnaires on the attributes of the meats while they were packaged, when they were unpackaged for cooking, and when they were eaten. The responses to each question were tabulated, and the probability of the X2 statistics was calculated for each table. There were no significant differences in the general acceptability of the steaks from the three storage treatments. Significant numbers of panelists judged that ground beef prepared from vacuum-packaged product was of better eolour and had less exudate, but was of poorer eating quality than the product from master packs. However, the majority of panelists did not distinguish between ground beef from the three storage treatments. The consumer responses indicate that controlled-atmosphere master packaging of display packs may offer a means of preserving display-ready beef for times that would allow wide distribution of the product through current commercial systems. INTRODUCTION The preparation of retail packs of meat at central facilities can have considerable economic benefits (Farris et al., 1991). However, the distribution of product prepared in current central-cutting operations is severely restricted by the limited 397
398
C. O. Gill, C. McGinnis, A. K. W. Tong
stability of meat packaged in conventional or high-oxygen modified-atmosphere display packs. A recent study of beef distribution, from a N o r t h American packing plant to a relatively close retail outlet, indicated that a storage life approaching 3 weeks is required for beef to be conveniently marketed. Such a lengthy period is needed because product must be stockpiled at both the wholesale and retail levels, to cope effectively with the fluctuating demands of customers (Gill & McGinnis, 1993). Under simulated commercial conditions, display-packaged ground beef and beef steaks achieved a storage life of 3 weeks or longer when they were master-packaged under oxygen-depleted atmospheres of N2 or CO2. After the master packs were opened, the product had a display life similar to that of vacuum-packaged product that was stored for the same time and ground, or cut into steaks, immediately before it was displayed (Gill & Jones, 1994a, b). Master packaging of retail-packaged product under oxygen-depleted atmospheres could then offer a general means o f preserving chilled beef during its distribution from central-cutting facilities. However, some indication of consumer reactions to product from such master packagings is required before commercial application of the technique can be considered. A study was therefore conducted to determine whether consumers were likely to discriminate against beef in retail packs that were stored for 3 weeks under oxygen-depleted atmospheres.
MATERIALS AND METHODS A consumer panel of 120 people was recruited to obtain a panel distributed with regard to sex, age, and family composition in proportions that approximate to those of the population o f Canada (Table 1). Names were selected at random from a local telephone directory. Persons were called in the order of selection of their names. Respondents who indicated a willingness to participate, and whose sex, age, and family circumstances corresponded with a vacant position in the panel, were recruited. Vacuum-packaged strip loins were obtained from a beef plant on the day after each animal was slaughtered. The loins were stored overnight at 2°C. Each loin was then divided into three portions. One portion was vacuum-packaged in a film that has an O2-transmission rate o f 40 cm 3 O2/m2/24h/atm at 25°C and 100% r.h. (Barrier film; Cryovac, Mississauga, ON, Canada). The other two portions TABLE 1 The Composition of the Consumer Panel that Evaluated Beef Samples Group
Men without resident family (19-60) Women without resident family (19-60) Men over 60 ~with or without Women over 60 /resident spouse Families with a child <10 Families with a child/children >10, or no children
Number
10 10 16 20 31 33
Acceptanceof master-packedbeef
399
were each divided into three steaks. Each steak was placed on a solid polystyrene tray with walls 25 mm high. Each filled tray was placed in a pouch of a shrinkable film that has antifogging properties and an O2-transmission rate of 11 000 cm3/ mZ/24h/atm at 25°C and 75% r.h. (RD 106; Cryovac). After being sealed, the pouch was shrunk to the tray by using a hot-air gun. A 3 mm hole made in the film at one corner of the tray allowed the film to form as a flat lid to the tray. The six display packs prepared from each loin were divided into two groups, and each group of three packs was master-packed in a pouch composed of a gas-impermeable aluminum-foil laminate (American National Can Co., Meenak, WI, USA). One pouch was filled with 3 litres of Nz and one with 3 litres of CO2 by using a packaging machine (Captron III; RMF, Grandview, MO, USA) that gives a pack atmosphere of either gas with a residual 02 concentration of <500 ppm. The loin origin of the contained product was identified on each vacuum and master pack. All the vacuum and master packs were stored at 2°C for between 21 and 23 days. Similarly, vacuum packs of beef trimmings were obtained from a beef plant on days in which the trimmings were packaged. Each 10 kg batch of trimmings was coarsely ground and then divided into three equal portions. One portion was vacuum-packaged. The other two portions were finely ground and then distributed into trays. Each tray contained 420 +20 g of ground beef, with the meat surface 5 mm below the top of the tray walls. Each tray was packaged in the film of high oxygen-permeability, and the display packs were master-packaged and stored as for the steaks. When product was to be distributed, the master packs and vacuum packs containing product from the same loin, or from the same batch of ground beef, were withdrawn. The master packs were opened, and the product was held in air at -1.5°C for 2 h to allow the meat to bloom. Display packs of steak or finely ground beef were prepared from the vacuum-packaged product. The samples were then distributed to panelists over a period of between 2 and 5 h. Each panelist received three steaks from the same loin, each steak having been subjected to a different storage treament, and three packs of ground beef from the same batch, each pack having been subjected to a different storage treatment. On delivery of the samples, the accompanying questionnaires (Table 2) were explained to each panelist. The questions on the fat perceived at each stage of each assessment were included as a control on the responses. In addition to answering the questions posed, the panelists were asked to record any comment they thought appropriate at each stage of the assessment. After the explanation of the requirements, the portions of the questionnaires that dealt with the appearance of the display-packaged meats were completed by the panelists. The panelists were asked not to freeze the steaks but to consume them within 3 days. They were also asked to store and prepare the ground meat as they would do for purchased product and to consume the ground meat within 14 days. After that time, the completed questionnaire was recovered from each panelist. The frequencies of the responses to each question were tabulated for each type of storage packaging. The probability of xZ-test statistic was calculated for each table according to the SAS (1990) frequency procedure. Tables for which the probability was <0.05 were considered to show dependence of the response frequency on the storage treatment. Such tables were examined to determine the differences in the response frequencies between the three storage treatments.
400
C. O. Gill, C McGinnis, A. K. IV. Tong
TABLE 2
The Questions and Possible Responses Contained in the Questionnaires on DisplayPackaged Beef Steaks and Ground Beef Product state preparation Packaged
Storage
Unpackaged
Preparation
Cooked
Question
Responses
General acceptability
very good, good, fair, neither poor nor good, poor, very poor
Exudate
too wet, about right, too dry
Colour
much too dark, too dark, just right, too light, much too light
Fat content
much too fatty, too fatty, just right, too lean, much too lean
Frozen or not frozen a
frozen, not frozen
Thawing method (if frozen) a
room, refrigerator, microwave
General acceptability
very good, good, fair, neither poor nor good, poor, very poor
Odour
very pleasant, pleasant, acceptable, unpleasant, very unpleasant
Exudate
too wet, about right, too dry
Colour
much too dark, too dark, just right, too light, much too light
Fat content
much too fatty, too fatty, just right, too lean, much too lean
Cooking method
grilled, fried, baked, boiled
Degree of cooking (if grilled or fried)
blue, rare, medium rare, well-done
General acceptability
very good, good, fair, poor, very poor
Odour b
very pleasant, pleasant, acceptable, unpleasant, very unpleasant very tender, tender, not tender enough, tough
Tenderness b Flavour b
very pleasant, pleasant, acceptable, unpleasant, very unpleasant
Fat content b
much too fatty, too fatty, just right, too lean, much too lean
a Questions asked for ground beef only. b Questions asked for steaks only.
Acceptanceof master-packedbeef
401
RESULTS Responses to the questions on fat content The fat content of the three samples of meat in any set were similar, so perceptions of different fat contents in the three samples could arise only from some biasing effect of the packaging treatments. In the event, the perceptions of differences in fat content by a few panelists were not significant. Responses to steaks With steaks, there were no significant differences in the response frequencies for the three storage treatments in the responses to the questions on the general acceptability of the meat when packaged, unpackaged, or cooked (Fig. 1). Despite that, there were significant (P<0.05) differences in the response frequencies to the question on the colour of the packaged meat and to the question concerning exudate in the unpackaged meat. The significant differences in response to the question on colour arose, despite >90% of the panelists scoring all steak colours as 'just right' because of a relatively high frequency (6%) of 'too dark' scores for steaks stored under Nz and of 'too light' scores for steaks stored under CO2. The significant differences in response to the question on exudate arose because steaks from the vacuum, N2, and CO2 storage treatments were, respectively considered 'too wet' by 6, 12 and 11% of panelists, and 'too dry' by 7, 0 and 6%. Responses to ground beef For packaged ground beef, the differences in the response frequencies for the three storage treatments were significant (P < 0-05) for the questions on general impression and colour, highly significant (P< 0-001) for the question on exudate, and not significant only for the question on fat content. Evidently, more of the product from vacuum than from master packs gave a 'very good' general impression, because product stored under N 2 w a s more frequently considered 'too dark', whereas product stored under CO2 was more frequently considered 'too wet' (Fig. 2). For unpackaged ground beef, there were no significant differences in the sets of responses to any question except that concerned with exudate. For the latter characteristic, a significant (P<0.05) number of panelists perceived that the product stored in vacuum pack had less exudate than the product stored under N2 or CO2, with the vacuum-packaged product being more frequently considered 'too dry' (Fig. 3). In response to the single question on cooked ground meat, a significant (P < 0.05) number of panelists perceived that the product stored in vacuum pack was of poorer quality than the product stored under N2 or CO2 (Fig. 4). Storage and preparation of the meats by panelists The steaks were grilled by 71% of the panelists and fried by 28%. The ground beef was frozen by 84% of the panelists. Of those who froze the meat, 54, 28, and 18% thawed the meat at room temperature, in a refrigerator, or by micro-
402
C. O. Gill, C. McGinnis, A. K: W. Tong Storage Treatment Vacuum
N 2 atmosphere
CO 2 atmosphere
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packaged
packaged
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0 a
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cooked
cooked
50
a
b
c
d
e
a
b
c
d
e
a
b
c
d
e
responses Fig. 1. The frequencies of responses to questions on the general acceptability of packaged, unpackaged, and cooked steaks. The responses were: a = very good, b = good, c = fair, d = neither poor nor good, e = poor. wave heating, respectively. The g r o u n d beef was grilled or fried by 60% o f the panelists, with the m e a t otherwise being c o o k e d in a variety o f boiled or b a k e d dishes. Panelists' comments
O f the panelists, 49 recorded c o m m e n t s on the steaks. O f these, 28 were wholly c o m p l i m e n t a r y a b o u t the m e a t f r o m all storage packagings. Only one or two panelists c o m m e n t e d adversely on the colour, odour, or tenderness o f meat, a n d
Acceptance of master-packed beef
403
Stora,qe treatment Vacuum
100
N ~ atmosphere
general impression
general impression
CO 2 atmosphere
general impression
50 -a b c d e o~ v
100
colour
a
b
c
d
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a b c d e colour
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I
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k
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m
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responses Fig. 2. The frequencies of responses to questions on the general acceptability and colour of, and the perception of exudate in, ground beef in display packs. The responses were: general impression, a -- very good, b -- good, c --- fair, d = neither good nor poor, e = poor; colour, f = much too dark, g = too dark, h = just right, i = too light, j = much too light; exudate, k = too wet, 1 -- about right, m= too dry. all such c o m m e n t s were a p p l i e d to the m e a t f r o m all three s t o r a g e p a c k a g i n g s . A d v e r s e c o m m e n t s o n e x u d a t e were m a d e with r e g a r d to m e a t s t o r e d u n d e r v a c u u m , N2, o r COz b y two, six, a n d six panelists, respectively. A d v e r s e c o m m e n t s o n f l a v o u r were m a d e w i t h r e g a r d to m e a t s t o r e d u n d e r v a c u u m , N2, o r CO2 b y two, t w o a n d five panelists, respectively. N i n e t e e n o f the panelists c o m m e n t e d o n the p a c k a g i n g . O f their c o m m e n t s , twelve were f a v o u r a b l e a n d o n e was u n f a v o u r a b l e , while 6 were c o n c e r n e d with w h e t h e r o r n o t the p a c k a g i n g c o u l d be recycled.
404
C. O. Gill, C. McGinn&, A. K. W.. Tong
Storage treatment Vacuum v
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COz atmosphere
100
E 0
Z3-
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b
h c
a
b
c
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b
c
responses
Fig. 3. The frequencies of responses to a question on the perception of exudate in ground beef that had been removed from display packs. The responses were: a = too wet, b = about right, c -- too dry. Some 52 panelists recorded comments on the ground beef. Of these, 23 were wholly complimentary about the meat from all storage packagings. The colour of meat from all storage packagings was commented on favourably by seven panelists. Six panelists commented on the colour of thawed meat from all storage packagings, three favourably and three unfavourably. Adverse comments on exudate were made with regard to meat stored under vacuum, N2, or CO2 by two, five, and five panelists, respectively. Adverse comments on the odour of cooked meat that had been stored under vacuum, N2, or CO2 were made by eight, one, and one panelists, respectively. Of eight comments on the
Storage treatment N;I atmosphere
Vacuum
CO = atmosphere
100 r"
so eo e~
Itl
•
0
abcd
e f
a b c d e f
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responses
The frequencies of responses to a question on the general acceptability of cooked ground beef. The responses were: a = very good, b = g o o d , c = f a i r , d = neither poor not good, e = poor, f = very poor. Fig. 4.
Acceptance of master-packedbeef
405
packaging, five were favourable, one was unfavourable, and two were concerned with recycling. DISCUSSION In the region where the trial was conducted, fresh meat is almost invariably retailed in a traditional (tray and overwrap) packaging. The display packaging used for the trial was necessarily constructed of commercially available trays and films. Because of this limitation, it was not possible to construct an overwrapped tray from which air could be reliably exhausted during the evacuation of master packs. Consequently, panelists were presented with meat in an unfamiliar, lidded type of tray. The panelists' comments suggest that any biasing of responses by the unfamiliar packaging would be favourable rather than otherwise. The questions on unpackaged ground beef did not include one on general acceptability. It seemed likely that the samples of ground beef in any set could be subjected to different storage and/or preparation treatments within some homes. Responses to a general question might then sometimes be founded on misleading recollections of the samples first unpackaged. It was considered that any such effect might be reduced by asking only specific questions. In contrast, comparison of specific eating qualities seemed inappropriate when the meat from different samples could be prepared in different ways at different times. Hence only one general question was asked on the eating quality of ground beef, with the intention of considering consumer comments for an explanation of any indication that a storage packaging had produced a particular effect. With packaged steaks, a small minority of panelists distinguished some colour differences between meat that had been stored under vacuum, N2, or CO2. However, these distinctions did not result in any significant differences in the ratings of general acceptability. Moreover, no adverse comment was made on colour by any panelist. It therefore seems that, if the storage packaging does affect the meat colour, the effect will be too small to be of any real consequence to consumers. It would be expected that steaks stored in a master package would lose more exudate than freshly cut steaks (Offer & Knight, 1988). The perception of excessive exudate when steaks were unpackaged in more of the master-packaged than the freshly cut steaks could then be expected. However, excessive free exudate in packs could be prevented by the use of an absorbent of adequate capacity. Such a simple adjustment of the packaging would seemingly eliminate any significant differences between steaks from the three storage packagings. A large fraction of panelists perceived that ground beef from master packs was darker, and had more exudate, than the product that was finely ground after being stored in a vacuum pack. The colour difference seemingly arose, at least in part, from the storage of coarsely ground meat in vacuum packs. This resulted in the fat's being stained by exudate. The pale pink fat in the finely ground product tended to lighten the perceived red colour of the mass. In contrast, the fat in the master.packaged product remained white, so the red colour perceived was that of the muscle tissue alone. The colour differences would then seem to have been due to the vacuum-packaged product appearing lighter red, rather than the master-packaged product appearing dark, than would freshly ground-beef trimmings.
406
C. O. Gill, C. McGinnis, A. K. W. Tong
As with the steaks, more exudate would be expected in the master-packaged ground beef than in that freshly prepared from vacuum-packaged product. Again, consumer perception of excessive exudate could be avoided by the use of a suitable absorbent. A significant number of panelists considered the ground meat prepared from vacuum-packaged product to have been of poorer eating quality than the product from master packs. The comments of some panelists indicate that their adverse response to the former was occasioned by their perceptions of off-flavours. It is possible that flavour deterioration in the coarsely ground, vacuum-packed product was related to the ingress of small quantities of oxygen through the packaging film (Jeremiah et al., 1992), while no such deterioration could occur in the product master-packed in a gas-impermeable film. The results of this study clearly suggest that consumers would find retail packs of beef from master packs with oxygen-depleted atmospheres as acceptable as product stored in vacuum pack and prepared for display only on the day of intended sale. Master packaging under oxygen-depleted atmospheres could then be a commercially useful means of preserving retail-ready beef during times adequate for the wide distribution of product from a central-cutting location. ACKNOWLEDGMENTS We thank Dr L. E. Jeremiah for his advice on consumer-testing procedures, and the Alberta Cattle Commission for its financial support of this study. REFERENCES Farris, D. E., Dietrich, R. A. & Ward, J. B. (1991). Meat Process. 30 (2), 60. Gill, C. O. & Jones, T. (1994a). Meat Sci., 37, 281. Gill, C. O. & Jones, T. (1994b). Meat Sci.., 38, 385. Gill, C. O. & McGinnis, C. (1993). Int. J. Food Microbiol., 18, 321. Jeremiah, L. E., Gill, C. O. & Penney, N. (1992). J. Muscle Foods, 3, 263. Offer, G. I. & Knight, P. (1988). In Developments in Meat Science, Vol. 4, ed. R. Lawrie. Elsevier Applied Science, London, p. 173. SAS (1990). SAS/STAT User's Guide, Version 6, 4th Ed. SAS Institute, Cary, NC, USA.