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bacon quality
Meat Science 64 (2003) 459–466 www.elsevier.com/locate/meatsci
The influence of diets containing either conventional corn, conventional corn with choice white grease, high oil corn, or high oil high oleic corn on belly/bacon quality G. Rentfrowa, T.E. Sauberb, G.L. Alleea, E.P. Berga,* a
University of Missouri, Department of Animal Sciences, Columbia, MO 65211, USA b Pioneer—A DuPont Company, Des Moines, Iowa, USA
Received 15 March 2002; received in revised form 1 August 2002; accepted 1 August 2002
Abstract The objectives of this study were to evaluate diets possessing different fatty acid profiles (as influenced by corn type) with regard to fatty acid profile and firmness of pork bellies. Crossbred barrows (n=196) were fed one of four corn-based diets consisting of conventional corn (CONV), CONV with choice white grease (CWG), high oil corn (HOC), or high oleic, high oil corn (HOHOC). Following 98 days on test, two animals representing the average pen weight (118 kg) were selected for harvest (n=56). A 50-g fat sample was removed from each belly for fatty acid profile analysis. Lateral and vertical flex tests were performed to determine belly firmness. Bellies were pumped and cooked according to a commercial protocol. Total saturated fatty acids increased (P< 0.001) and total unsaturated fatty acids decreased (P< 0.05) when CWG was added to the CONV diet or when HOC or HOHOC were substituted for CONV corn. Pigs fed CONV corn had firmer bellies, while those fed HOC were softer. No differences were observed across treatment for percentage pump retention, smokehouse yield, or slicing yield (P >0.05). Based on the results of this study, corn type influences fatty acid profile, and belly firmness, but does not affect pump retention, or slicing yields. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: Belly; Bacon; Corn-type; Fatty acid profile
1. Introduction Typically pork fat contains high concentrations of saturated fatty acids and lower concentrations of monoand poly-unsaturates (Miller, Shackelford, Hayden, & Reagan, 1990). The fatty acid profile of pork fat can influence processing properties (Shackelford et al., 1990; St. John et al., 1987), while the consumption of saturated fatty acids by humans may increase ldl-cholesterol, resulting in an increased risk of coronary heart disease. Research in swine nutrition has shown that the fatty acid profile of pork fat can be altered by feeding diets that contain variations in the concentrations of fatty acids (Fontanillas, Barroeta, Baucells, & Guardiola, 1998; Larick, Turner, Schoenherr, Coffey, &
* Corresponding author. Tel.: +1-573-882-3176; fax: +1-573-8844606. E-mail address: [email protected] (E.P. Berg).
Pilkington, 1992; Miller et al., 1990). One method of altering the fatty acid profiles of pork tissue is to feed oils/oil seeds high in oleic acid (Miller et al., 1990; Shackelford et al., 1990; St. John et al., 1987) or other unsaturated fats (Leszczynski et al., 1992; Mazhar et al., 1990; Miller et al., 1990; Myer, Johnson et al., 1992; Myer, Lamkey, Walker, Brendemuhl, & Combs, 1992; Romans, Johnson, Wulf, Libal, & Costello, 1995a, 1995b; Shackleford et al., 1990). While decreasing the content of saturated fat in pork may provide a human health benefit, feeding diets high in mono- and poly unsaturates may have adverse affects on pork belly/ bacon quality (Shackelford et al., 1990; St. John et al., 1987). Utilizing traditional plant breeding techniques, high oil corn varieties with either high linoleic acid or high oleic acid/low polyunsaturated fatty acid profiles have been developed. The objective of this research was to characterize the effects of feeding these corn varieties with modified fatty acid content on belly/ bacon parameters.
0309-1740/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(02)00215-2
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Table 1 Phase 5 Finisher diet (all ingredients are shown as a percentage of the composition of the diet) Ingredient
CONV
CWG
HOC
HOHOC
Ground normal corn Ground high oil corn (HOC) Ground high oil, high oleic corn (HOHOC) Soybean meal (48%) Choice white grease Dicalcium phosphate Limestone Salt Swine vitamin mixa Swine mineral mixb l-Lysine HCL Antibiotic premixc
86.25 – – 11.35 – 0.840 0.650 0.500 0.150 0.100 0.100 0.025
79.785 – – 12.95 4.91 0.840 0.640 0.500 0.150 0.100 0.100 0.025
– 85.745 – 11.90 – 0.840 0.640 0.500 0.150 0.100 0.100 0.025
– – 85.27 11.90 – 0.840 0.640 0.500 0.150 0.100 0.100 0.025
a Supplied per kilogram of diet: vitamin A, 6600 IU; vitamin D3, 660 IU; vitamin E, 13.2 IU; vitamin K, 2.39 mg; vitamin B12, 0.018 mg; riboflavin, 4.95 mg; pantothenic acid, 16.83 mg; niacin, 19.80 mg. b Supplied mg/kg diet: Zn, 110; Fe, 110; Mn, 22; Cu, 11; I, 0.198; Se, 0.198. c Supplied mg/kg: bacitracin methylene disalicylate.
2. Materials and methods 2.1. Animals Crossbred barrows (EBGenepacker; n=196) were blocked by weight and randomly assigned to one of four treatments consisting of a control finishing diet containing normal corn and no added fat (CONV), normal corn and choice white grease (CWG), high-oil corn (HOC), and high-oil, genetically enhanced corn to be high in concentration of oleic acid (HOHOC). Pigs were fed a five-phase corn-soybean meal diet sequence, with a constant ratio of lysine to metabolizable energy (ME). Experimental diets were formulated based on the chemical analysis of the corn used. Both high oil corn were included in the diets at the same percentage, since they had similar (6.5%) fat content. An example of the phase 5 finisher diets are shown in Table 1. Fatty acid profiles of the corn sources can be found in Table 2. Pigs were arranged seven pigs per pen in 28 pens for a total of 49 pigs per treatment, and fed a five-phase corn-soybean meal diet sequence, where each diet had a constant ratio of lysine to metabolized energy. Experimental diets were Table 2 Fatty acid profiles of the various corn sources Fatty acid (%)
CONV
HOC
HOHOC
Palmitic, 16:0 Palmitoleic, 16:1 Stearic, 18:0 Oleic, 18:1 Linoleic, 18:2 Linolenic, 18:3
10.3 0.10 1.90 33.1 52.0 1.20
9.90 0.10 2.90 37.2 49.2 1.00
9.40 0.10 2.20 58.2 27.7 1.10
CONV=Conventional corn; HOC=high oil corn; HOHOC=high oleic, high oil corn.
formulated based on the chemical analysis of the corn used. Both high oil corns were included in the diets at the same percentage since they had similar fat contents (6.5%). Barrows had ad libitum access to feed and water and were fed to an average end weight of 118 kg. The University of Missouri Animal Care and Use Committee approved the production and research protocol. Following 98 d on test, two pigs representing the pen average (118 kg), were selected from each pen for humane slaughter at the University of Missouri abattoir (n=56). 2.2. Fresh belly fabrication and measurements Bellies were removed from the carcasses side and processed according to Institutional Meat Purchasing Specifications (IMPS #408; NAMP, 1997). Spareribs and related cartilage were removed, the bellies were squared (approximately 35.648.3 cm), and all remaining leaf fat removed. The fresh bellies with the skin on were evaluated by an objective flex test performed by centering the squared belly, fat side down, on a 7.6 cm diameter polyvinyl chloride (PVC) pipe mounted perpendicular to a board marked with a 2.54-cm grid matrix (Fig. 1). Lateral and vertical flex were determined from the degree of belly flex relative to the grid matrix. A lateral belly flex of zero meant the belly was completely parallel to the floor and was completely stiff. A vertical belly flex of 6 meant that the belly flexed to a point where there were 15.2 cm between the ends of the squared belly. Thus, a lower vertical and a higher lateral flex would indicate a firmer belly. Upon completion of the belly flex test, each squared belly was individually tagged with the appropriate identification, vacuum packaged, and frozen at 22 C for later processing.
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Fig. 1. Measuring lateral and vertical belly flex. (a) This illustrates a lower lateral, higher vertical flex; firmer belly. (b) This illustrates a higher lateral, lower vertical flex; softer belly.
2.3. Fatty acid profiles One slice was removed from the shoulder (cranial) end of the fresh belly slab and a 50-g sample of leaf (peritoneal) fat was collected from each belly, individually packaged, and frozen for transport to Dupont Specialty Grains (Des Moines, IA) for fatty acid profile analysis. Fatty acid analysis was performed using the modified method described by Park and Goins (1994), and Loor and Herbein (1998). In addition, the various corn samples utilized during the finishing period were analyzed with the same procedure as stated above. 2.4. Bacon processing and measurements Uncooked bellies were thawed (4 C) for 24 h and transported to a commercial packing plant where they were skinned, and weighed before (green weight) and after injection (pumped weight). The bellies were pumped fat side down using a Townsend multi-needle bacon injection pump (Townsend Inc., Des Monies, IA). A commercial brine (Excel Inc., Ottumwa, IA) was injected to 112% of the bellies green weight and allowed to drain to 110% of the green weight. The commercial brine consisted of 1.5% salt, 0.3% sugar, 0.3% sodium phosphate, 0.055% sodium erythorbate, 0.012% sodium nitrite. Bellies were hung by a bacon comb attached at the flank end and heat processed according to the plants commercial protocol. Following processing, bacon was removed from the smokehouse, showered for 10 min, drip dried for 10 min, and then chilled overnight at 3 C. The following morning, individual bacon slabs were weighed to determine smokehouse yield and placed in a tempering cooler (4 C) to facilitate optimal pressing and slicing. Full bacon slabs were pressed using a
commercial bacon press (Anco, Cherry-Burrell AMCA International Anco/Votator Division, Louisville, KY) and then sliced by a high-speed slicer at nine slices per 2.54 cm. The full sliced bacon drafts were placed on slip-sheets (complete with all ends and pieces) and placed in wax-coated boxes. Boxes were sealed and properly labeled for delivery to the University of Missouri Meat Science Laboratory. During high-speed slicing, it was necessary to use more than one slip-sheet to accommodate the entire bacon slab. During collection of the sliced bacon slabs, some partial slabs were placed in the boxes out of order. Therefore, 29 full bacon slabs were positively identified by matching lean and fat patterns within the bacon slices or on the exterior of the sparerib side of the slab. Slicing yield was the only processing variable affected by the mishandling. The number of bacon slabs remaining for analysis were as follows; CONV, n=7; CWG, n=7; HOC, n=6, and HOHOC, n=9. Slicing yield was determined by weighing (Fairbanks model H90–167–1, Fairbanks Scales, St. Johnsbury VT) the center portions of the bacon slab after the removal of comb marks and all incomplete slices. The remaining bacon slab, containing only commercially acceptable slices, was divided into five separate sections and labeled as, A, B, C, D, and E (Fig. 2; Mandigo, 1998). The first two slices from the cranial end were removed from each section and evaluated for fracture analysis. A trained person evaluated fracture analysis by rolling the bacon slice over the forefinger. A fracture was considered as lateral or vertical cracks in the structural integrity of the bacon slice. Subjective fracture analysis was performed by dividing the slice into four quadrants along the length of the bacon slice and assigning a score for each quadrant. The scores were then averaged for each slice. A score of
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Fig. 2. Sampling diagram for draft of sliced bacon.
0 indicated that no visual cracks or shattering could be detected, the scoring increased in severity with 2, 3, 4, 5, and a score of 6 being indicative of a ‘‘spider-web’’ consistency of shattering within the fat of the bacon slice (Mandigo, 1998). Five bacon slices per slab, representing one slice from each section (described earlier), were cooked (top and bottom plate=177 C; plate height=0.4 cm) on a MagiGrill PGB-60 (Magikich’n, Quackertown, PA) double belt conveyor cooker. Preliminary testing was conducted to verify the degree of doneness (golden brown; not crisp) and an automated setting for conveyor speed and upper and lower belt cooking temperatures. Cooked slice yield was targeted to be 40% of the original bacon slice weight. Each slice was weighed before and after cooking to the nearest 0.1 g (Ainsworth model CR-8101, Denver Instruments Co., Denver CO). After cooking, slices were allowed to cool for 10 min at room temperature on absorbent paper towels. Cooking loss was calculated as ((raw weightcooked weight)/raw weight)100. Bacon slice length was measured to the nearest 0.3 cm before and after cooking. Bacon slice cooking shrink (length change) was calculated as ((raw lengthcooked length)/raw length)100. Subjective evaluation of cooked slice visual distortion was evaluated using a 5-point distortion scale where 1 represented a mostly flat slice, and as severity of curling increased samples were rated 2, 3, 4, and 5 where 5 indicated a slice that completely curled with no flat areas on the slice (Fig. 3). 2.5. Statistical analysis The data was analyzed utilizing the Proc GLM procedure of SAS (SAS Institute, Cary, NC) and Least Square means were tested with the fixed effect of the treatments and then least square means tested for least significant differences. An alpha of P < 0.10 was considered a trend and a significant difference was set as an alpha of P < 0.05. Pearson correlation coefficients were calculated between fatty acid profiles, processing parameters, and belly quality (flex test).
Fig. 3. Numeric scale and examples for subjective visual evaluation of cooked bacon slice distortion.
3. Results and discussion 3.1. Fatty acid profile determination Several researchers have noted that the level of saturated fat in pork fat could be altered by the inclusion of unsaturated fat in the diet (Fontanillas et al., 1998; Larick et al., 1992; Leszczynski et al., 1992; Mazhar et al., 1990; Miller et al., 1990; Myer, Johnson et al., 1992; Myer, Lamkey et al., 1992; Romans et al., 1995a, 1995b; Shackleford et al., 1990). The fatty acid (FA) profile obtained from a slice taken from the fresh belly at 24 h postmortem differed across dietary treatments (Table 3). The total saturated fatty acids (SFA) decreased (P < 0.01) and total unsaturated fatty acids (UFA) increased (P < 0.05) with the addition of CWG, HOC, or HOHOC to the diet. The highest concentration of monounsaturated fatty acids (MUFA; P < 0.05) was found in the fat of pigs fed HOHOC, whereas the lowest concentration was found in the fat of pigs fed the CONV and HOC treatments. The increase in UFA and the decrease in SFA agree with other studies that have fed high oleic feedstuffs to pigs (Mazhar et al., 1990; Miller et al., 1990; Myer, Johnson et al., 1992; Myer, Lamkey et al., 1992; Shackelford et al., 1990). Past research has shown a decrease in SFA and an increase in MUFA and PUFA concentrations when diets were supplemented with oil seeds (sunflower, safflower, and canola) high in oleic acid (Miller et al., 1990; Myer, Lamkey et al., 1992), however, Myer, Lamkey et al. (1992) only noted a slight increase in MUFA concentration. In the current study, the highest concentration in
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G. Rentfrow et al. / Meat Science 64 (2003) 459–466 Table 3 Fatty acid LSMEANS and standard error for fresh bellies by treatment Fatty acid
Structure
CONV
CWG
HOC
HOHOC
SE
Significance
Capric Lauric Myristic Palmitic Palmitoleic Heptadecanoic Heptadecanoic Stearic Oleic Oleic Linoleic Linoleic Arachidic Eicosenoic Linolenic Eicosadienoic Eicosadienoic Eicosadienoic Arachidonic Docosatetraneoic CLA SFA UFA MUFA PUFA
C10:0 C12:0 C14:0 C16:0 C16:1 C17:0 cis10 C17:1 C18:0 C18:1trans C18:1cis C18:2trans C18:2cis C20:0 C20:1 C18:3 cis11, 14 C20:2 cis8, 11, 14 C20:3gamma cis11, 14, 17 C20:3 C20:4 C22:4
0.084ab 0.074 1.410 25.212b 2.722 0.363 0.333 12.627c 0.264b 44.228a 0.080a 9.046b 0.234b 0.813 0.343a 0.399b 0.075a 0.048a 0.223a 0.091a 0.145a 40.003b 58.664a 48.359a 10.306b
0.078a 0.074 1.388 24.057a 2.707 0.328 0.307 11.464b 0.292c 45.666b 0.107b 9.814c 0.186a 0.805 0.386b 0.430b 0.083b 0.054b 0.262b 0.103b 0.164b 37.574a 61.016bc 49.778b 11.238c
0.088b 0.078 1.426 24.024a 2.716 0.328 0.283 10.601a 0.222a 43.752a 0.080a 12.871d 0.220ab 0.728 0.353a 0.496c 0.087b 0.043a 0.273b 0.114c 0.144a 36.764a 62.018c 47.701a 14.317d
0.084b 0.079 1.486 24.583ab 2.758 0.338 0.304 10.922ab 0.250b 47.438c 0.084a 8.197a 0.202ab 0.831 0.359a 0.326a 0.069a 0.045a 0.226a 0.088a 0.141a 37.694a 60.975b 51.581c 9.395a
0.002 0.002 0.130 0.236 0.084 0.020 0.019 0.208 0.007 0.350 0.006 0.270 0.012 0.028 0.008 0.015 0.003 0.002 0.009 0.003 0.005 0.376 0.368 0.376 0.300
P< 0.05 NS NS P< 0.01 NS NS NS P< 0.01 P< 0.01 P< 0.01 P< 0.01 P< 0.05 P< 0.01 NS P< 0.05 P< 0.01 P< 0.05 P< 0.05 P< 0.01 P< 0.05 P< 0.01 P< 0.01 P< 0.05 P< 0.05 P< 0.05
Means within a row with different letters differ significantly. CONV=Conventional corn; CWG=Choice white grease; HOC=High oil corn; HOHOC=High oil, high oleic corn; CLA=Conjugated linoleic acid; SFA=Saturated fatty acids; UFA=Unsaturated fatty acids; MUFA= Monounsaturated fatty acids; PUFA=Polyunsaturated fatty acids.
MUFA occurred in the pigs fed HOHOC. The HOC treatment possessed the highest concentration of UFA in this study and tended to have the highest slicing yield (exhibiting a trend at P< 0.10; Table 4). The pigs fed CONV possessed the highest percentage of SFA and the lowest USF concentration, and had the lowest vertical (a lower vertical flex=a firmer belly) and highest lateral flex test (a higher lateral flex=a firmer belly). Likewise, the HOC fed pigs had bellies with the highest percentage of UFA and the highest vertical and lowest lateral flex (Table 5). Which would indicate a ‘‘softer’’ belly; however, the softer belly did not result in poorer slice-ability. According to Pork Composition and Quality Assessment Procedures (NPPC, 2000), quality pork fat must have < 15% polyunsaturated fatty acids (PUFA) and > 15% stearic acid (18:0). Furthermore, pork fat containing > 14% linolenic acid (C18:2) is associated with soft fat. In the present study, HOC approached the 15% limit for PUFA (14.32%; Table 3). None of the dietary treatments resulted in deposition of > 15% stearic acid and none contain > 14% linolenic acid. The results of this study would suggest that even though dietary fatty acid profile was altered, an acceptable FA composition was achieved across each treatment group resulting in adequate belly firmness and, subsequently, acceptable slice-ability.
Correlation coefficients between selected FA concentration and fresh belly and bacon parameters are reported in Table 6. Significant correlations were seen between PUFA and lateral and vertical belly flex (r=0.3906 and 0.4773, respectively) and shatter score (r=0.5835). In this study, the saturated fat palmitic acid was more highly correlated with lateral (r=0.5000) and vertical (r=0.4705) belly flex than was stearic acid. Palmitic acid also had a significant (P=0.02) positive correlation (r=0.3384) with shatter score, suggesting that evidence of shattering increases as the percentage of palmitic acid increases. Significant correlations were seen between linolenic acid (C18:2) and lateral (r=0.3810) and vertical (r=0.4713) belly flex and shatter score (r=0.5844). Mazhar et al. (1990) and Shackleford et al. (1990) noted that the addition of canola (ground or oil) to the diet produced softer bacon, as evaluated by a trained sensory panel. In addition, Miller et al. (1990) found that pig diets supplemented with high oleic oil seeds (sunflower, safflower, and canola oils) had softer, oilier fat than controls. Furthermore, Myer, Johnson et al. (1992) and Myer, Lamkey et al. (1992) found that pigs fed high oil peanuts and/or canola oil had softer fat, than their unsupplemented counterparts. A primary focus of this study was to evaluate genetically enhanced high oleic, high oil corn. Table 3 shows
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Table 4 Least squares means and standard errors for slicing yield of bacon slabs after high-speed slicing Variable a
Number of bacon slabs used in evaluation High-speed slicing yieldb(%)
CONV
CWG
HOC
HOHOC
SE
Significance
7 78.24ab
7 70.27a
6 84.07b
9 70.12a
4.90
P< 0.10
Means within a row with different letters differ significantly. a Slicing yield evaluated on full center section bacon slabs positively identified at the Excel packing plant. b Slicing yield=(weight of intact, full-length center slices/cooked pressed weight)100.
LSMEANS indicating that the HOHOC treatment resulted in a significantly higher concentration of oleic acid in the fat tissue of the fresh pork belly. These results are in agreement with other studies that showed an increase in oleic acid deposited in fat tissue when diets were supplemented with oils high in oleic acid concentrations (Miller et al., 1990; Myer, Johnson et al. 1992; Shackelford et al., 1990). Oleic acid (C18:1 cis) concentrations had no significant correlation with any of the processing parameters reported in Table 6, however, a significant (P=0.038) negative correlation (r=0.3877) was observed for slicing yield (Table 6), indicating that as the concentration of C18:1 cis increased, slicing yield decreased. The variant C18:1 trans was significantly (P=0.049) correlated only to shatter score (r=0.2888). Shackelford et al. (1990) indicated an increased concentration of oleic acid (18:1) in pork fat noting a decrease in bacon slicing yields as a result of supplementing canola oil, which is in agreement with this study.
3.2. Processing and cooking yields No differences were observed across treatments for green weight, pumped weight, pressed center weight, or smokehouse yield (Table 5). Furthermore, no differences were observed across dietary treatments for the cooked bacon parameters of cooking loss, cooked length shrink, or visual distortion score (Table 5). It can be concluded that dietary treatment had no affect on the yield of fresh pork belly, yield of processed un-sliced bacon, or cooking yield. Pigs fed HOC had lower bacon slice fracture scores (P < 0.01), however no differences were observed between the other dietary treatments (Table 5). These data coincide with findings of Shackelford et al. (1990) in which pump yield and overall yield of bellies/bacon were not affected by supplementing pig diets with animal fat, sunflower oil, safflower oil, or canola oil. However, Shackelford et al. (1990) did find that dietary treatments produced higher cooking yields than controls, and the addition of canola oil lowered
Table 5 Least squares means and standard errors for bacon processing Variable a
Fresh belly, Vertical flex (inches) Fresh belly, Lateral flex (inches)b Green weight (pre-pump) (lbs.) Pump percentagec (%) Cooked pressed center weight (lbs.) Smokehouse yieldd (%) Shattere Bacon slice cooking lossf (%) Bacon slice cooking shrinkg (%) Cooked bacon slice visual scoreh
CONV
CWG
HOC
HOHOC
SE
Significance
14.14a 10.21c 8.31 13.98 6.87 88.54 3.46b 58.00 29.75 2.18
16.13b 8.32ab 8.90 13.42 7.11 90.21 3.44b 60.04 31.39 2.36
16.00b 7.71a 8.60 13.37 7.65 91.59 2.55a 57.89 30.38 2.21
15.42b 8.89abc 8.85 13.82 7.00 91.14 3.46b 57.46 31.14 2.27
0.459 0.535 0.250 0.269 0.635 1.398 0.243 1.13 1.19 0.121
P< 0.05 P< 0.05 NS NS NS NS P< 0.01 NS NS NS
Means within a row with different letters differ significantly. a Recorded as the summation of vertical flex from right and left ends of loin or belly whereby zero flex would be flat; a vertical flex reading of ‘‘800 would be equivalent to the left side of the loin/belly flexing to a point of 4-inches on the left and 4-inches on the right. A lower vertical flex would be a firmer loin/belly. b Recorded as the summation of lateral flex from right and left ends of loin or belly whereby a zero lateral flex would be a complete folding of the loin/belly; a lateral flex reading of ‘‘800 would be equivalent to 8 inches separating the opposing ends. A higher lateral flex would be a firmer loin/ belly. c Pump percentage=((pumped belly weightgreen weight)/green belly weight)100. d Smokehouse yield=(Cooked pressed center weight/pumped weight)100. e Subjective evaluation of slice integrity (fracture) from 0 to 6 where 0=intact slice possessing no shatter and 6=‘‘spider-web’’ fracture. f Bacon slice cooking loss=((raw weightcooked weight)/raw weight)100. g Bacon slice cooking shrink=((raw lengthcooked length)/raw length)100. h Subjective evaluation of slice appearance (curling, cooked distortion) from 0 to 6 where 0=flat slice with no distortion and 6=extreme curling and distortion.
(0.5099) (0.7571) (0.3373) (0.1153) (0.3621) (0.5278) (0.0758) (0.8178) (0.5186) (0.2196) (0.5649) 0.0964 0.0453 0.1400 0.2279 0.1331 0.0924 0.2560 0.0338 0.0944 0.1786 0.0843 (0.1657) (0.4583) (0.1528) (0.2603) (0.0833) (0.8825) (0.0719) (0.7945) (0.5046) (0.4792) (0.9378) 0.1991 0.1073 0.2052 0.1622 0.2474 0.0214 0.2567 0.0378 0.0966 0.1024 0.0113 (0.7033) (0.4299) (0.5537) (0.4188) (0.0173) (0.3937) (0.5283) (0.7971) (0.7687) (0.5581) (0.4405) 0.0552 0.1142 0.0858 0.1169 0.3354 0.1233 0.0913 0.0373 0.0427 0.0848 0.1116 0.3384 0.2761 0.2888 0.2412 0.0382 0.5844 0.2093 0.3751 0.4389 0.2499 0.5835 Palmitic acid (C16:0) Stearic acid (C18:0) Oleic acid (C18:1 trans) Oleic acid (C18:1 cis) Linoleic acid (C18:2 trans) Linoleic acid (C18:2 cis) CLA SFA UFA MUFA PUFA
0.5000 0.3662 0.1263 0.0120 0.1436 0.3810 0.1341 0.4923 0.4417 0.0115 0.3906
(0.0001) (0.0047) (0.3446) (0.9286) (0.2823) (0.0032) (0.3155) (0.0001) (0.0005) (0.9315) (0.0024)
0.4705 0.3510 0.1219 0.0202 0.1118 0.4713 0.1390 0.4712 0.5018 0.0495 0.4773
(0.0002) (0.0069) (0.3618) (0.8804) (0.4032) (0.0002) (0.2980) (0.0002) (0.0001) (0.7122) (0.0002)
0.2678 0.0411 0.0401 0.2151 0.1704 0.0236 0.2494 0.1405 0.1992 0.1924 0.0116
(0.0550) (0.7723) (0.7777) (0.1256) (0.2272) (0.8681) (0.0746) (0.3205) (0.1569) (0.1717) (0.9348)
0.0369 0.0971 0.0615 0.1152 0.2442 0.0138 0.0253 0.0788 0.0771 0.0898 0.0183
(0.7949) (0.4934) (0.6650) (0.4160) (0.0810) (0.9228) (0.8585) (0.5785) (0.5872) (0.5267) (0.8976)
0.0367 0.0522 0.0531 0.1232 0.0124 0.1861 0.0404 0.0664 0.0747 0.1418 0.1891
(0.8155) (0.7394) (0.7355) (0.4311) (0.9370) (0.2322) (0.7969) (0.6721) (0.6340) (0.3645) (0.2245)
0.0635 0.1123 0.2023 0.3877 0.0503 0.2845 0.1985 0.0398 0.0273 0.3348 0.2772
(0.7434) (0.5618) (0.2926) (0.0377) (0.7955) (0.1347) (0.3019) (0.8377) (0.8882) (0.0758) (0.1455)
Shatter score Slicing yield Smoked center bacon slab weight Smokehouse yield Pumping percent Fresh belly, lateral flex Fresh belly, vertical flex
Table 6 Pearson correlation coefficients (and probability>|R| under Ho) between select bacon processing parameters and fatty acid content
(0.0200) (0.0603) (0.0490) (0.1024) (0.7989) (0.0001) (0.1580) (0.0094) (0.0020) (0.0903) (0.0001)
Cooked, weight loss
Cooked slice shrinkage
Cooked, visual score
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slicing yields. These observations were not seen in the present study. Mazhar et al. (1990) added ground canola seed to the diet and noted that green weight yield, smokehouse yield, and cooking yield were not affected by treatment; this is consistent with the present study. Canola seed/oil, sunflower oil and safflower oil are all high in oleic acid, which makes these studies a notable comparison to feeding high oleic corn.
4. Conclusions The results of this study indicate that the fatty acid profile of the diet, as influenced by corn type, had no effect on green weight, pumped weight, smokehouse yield, or pressed center weight. In addition, there were no differed for the cooked bacon slice parameters of cooking loss, cooked length shrink, or visual distortion score. However, dietary treatment influenced pork fatty acid profile, with the highest concentration of saturated fatty acids in pork from pigs fed the conventional corn and the highest concentration of total unsaturated fatty acids in pork form pigs fed the high oil corn diets. Even though the dietary treatments produced softer bellies compared to the conventional corn treatment, there were no adverse effects to belly/bacon quality parameters.
Acknowledgements The authors would like to thank DuPont Specialty Grains for assistance with this research project. In addition, the authors would like to thank Dr. Doug Sutton, the Excel Corporation, Dr. Mike Linville, Chad Stahl, and Kasey Maddock for their help throughout this project.
References Fontanillas, R., Barroeta, A., Baucells, M. D., & Guardiola, F. (1998). Backfat fatty acid evolution in swine fed diets high in either cismonounsatruaed, trans, or (n-3) fats. Journal of Animal Science, 76, 1045–1055. Larick, D. K., Turner, B. E., Schoenherr, W. D., Coffey, W. T., & Pilkington, D. H. (1992). Volatile compound content and fatty acid composition of pork as influenced by linolenic acid content of the diet. Journal of Animal Science, 70, 1397–1403. Leszczynski, D. E., Pikul, J., Easter, R. A., McKeith, F. K., McLaren, D. G., Novakofski, J., Bechtel, P. J., & Jewell, D. E. (1992). Effect of feeding finishing pigs extruded full-fat soybeans on performance and pork quality. Journal of Animal Science, 70, 2167–2174. Loor, J. J., & Herbein, J. H. (1998). Exogenous conjugated linolenic acid isomers reduce bovine milk fat concentration and yield by inhibiting de novo fatty acid synthesis. Journal of Nutrition, 128, 2411–2419. Mandigo, R. 1998. Belly and bacon quality. In Pork quality and safety summit (pp. 239–249). National Pork Producer. Mazhar, A., Busboom, J. R., Field, R. A., Rule, D. C., Heald, T.,
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Russell, W. C., & McCormick, R. J. (1990). Functional characteristics, fatty acid composition and palatability of bacon from pigs fed canola. Journal of Food Science, 55, 575–576. Miller, M. F., Shackelford, S. D., Hayden, K. D., & Reagan, J. O. (1990). Determination of the alteration in fatty acid profiles, sensory characteristics and carcass traits of swind fed elevated levels of monounsaturated fats in the diet. Journal of Animal Science, 68, 1624–1631. Myer, R. O., Lamkey, J. W., Walker, W. R., Brendemuhl, J. H., & Combs, G. E. (1992). Performance and carcass characteristics of swine when fed diets containing canola oil and added copper to alter the unsaturated:saturated ratio of pork fat. Journal of Animal Science, 70, 1417–1423. Myer, R. O., Johnson, D. D., Knauft, D. A., Gorbet, D. W., Brendemuhl, J. H., & Walker, W. R. (1992). Effect of feeding high-oleicacid peanuts to growing-finishing swine on resulting carcass fatty acid profile and on carcass and meat quality characteristics. Journal of Animal Science, 70, 3734–3741. NPPC (2000). Pork compostition and quality assessment procedures. Des Moines, IA: National Pork Producers Council. NAMP (1997). The meat buyers guide (3rd ed.). Reston, VA: North American Meat Processors.
Park, P. W., & Goins, R. E. (1994). Preparation of FAME for analysis of fatty acid composition in foods. Journal of Food Science, 59, 1262–1266. Romans, J. R., Johnson, R. C., Wulf, D. M., Libal, G. W., & Costello, W. J. (1995a). Effects of ground flaxseed in swine diets on pig performance and on physical and sensory characteristics and omega-3 fatty acid content of pork: I. Dietary level flaxseed. Journal of Animal Science, 73, 1982–1986. Romans, J. R., Johnson, R. C., Wulf, D. M., Libal, G. W., & Costello, W. J. (1995b). Effects of ground flaxseed in swine diets on pig performance and on physical and sensory characteristics and omega-3 fatty acid content of pork: II. Duration of 15% dietary flaxseed. Journal of Animal Science, 73, 1987–1999. Shackelford, S. D., Miller, M. F., Haydon, K. D., Lovegren, N. V., Lyon, C. E., & Reagan, J. O. (1990). Acceptability of bacon as influenced by the feeding of elevated levels of monounsaturated fats to growing-finishing swine. Journal of Food Science, 55, 621–624. St. John, L. C., Young, C. R., Knabe, D. A., Thompson, L. D., Schelling, G. T., Grundy, S. M., & Smith, S. B. (1987). Fatty acid profiles and sensory and carcass traits of tissues from steers and swine fed an elevated monounsaturated fat diet. Journal of Animal Science, 64, 1441.
The influence of diets containing either conventional corn, conventional corn with choice white grease, high oil corn, or high oil high oleic corn on belly/bacon quality G. Rentfrowa, T.E. Sauberb, G.L. Alleea, E.P. Berga,* a
University of Missouri, Department of Animal Sciences, Columbia, MO 65211, USA b Pioneer—A DuPont Company, Des Moines, Iowa, USA
Received 15 March 2002; received in revised form 1 August 2002; accepted 1 August 2002
Abstract The objectives of this study were to evaluate diets possessing different fatty acid profiles (as influenced by corn type) with regard to fatty acid profile and firmness of pork bellies. Crossbred barrows (n=196) were fed one of four corn-based diets consisting of conventional corn (CONV), CONV with choice white grease (CWG), high oil corn (HOC), or high oleic, high oil corn (HOHOC). Following 98 days on test, two animals representing the average pen weight (118 kg) were selected for harvest (n=56). A 50-g fat sample was removed from each belly for fatty acid profile analysis. Lateral and vertical flex tests were performed to determine belly firmness. Bellies were pumped and cooked according to a commercial protocol. Total saturated fatty acids increased (P< 0.001) and total unsaturated fatty acids decreased (P< 0.05) when CWG was added to the CONV diet or when HOC or HOHOC were substituted for CONV corn. Pigs fed CONV corn had firmer bellies, while those fed HOC were softer. No differences were observed across treatment for percentage pump retention, smokehouse yield, or slicing yield (P >0.05). Based on the results of this study, corn type influences fatty acid profile, and belly firmness, but does not affect pump retention, or slicing yields. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: Belly; Bacon; Corn-type; Fatty acid profile
1. Introduction Typically pork fat contains high concentrations of saturated fatty acids and lower concentrations of monoand poly-unsaturates (Miller, Shackelford, Hayden, & Reagan, 1990). The fatty acid profile of pork fat can influence processing properties (Shackelford et al., 1990; St. John et al., 1987), while the consumption of saturated fatty acids by humans may increase ldl-cholesterol, resulting in an increased risk of coronary heart disease. Research in swine nutrition has shown that the fatty acid profile of pork fat can be altered by feeding diets that contain variations in the concentrations of fatty acids (Fontanillas, Barroeta, Baucells, & Guardiola, 1998; Larick, Turner, Schoenherr, Coffey, &
* Corresponding author. Tel.: +1-573-882-3176; fax: +1-573-8844606. E-mail address: [email protected] (E.P. Berg).
Pilkington, 1992; Miller et al., 1990). One method of altering the fatty acid profiles of pork tissue is to feed oils/oil seeds high in oleic acid (Miller et al., 1990; Shackelford et al., 1990; St. John et al., 1987) or other unsaturated fats (Leszczynski et al., 1992; Mazhar et al., 1990; Miller et al., 1990; Myer, Johnson et al., 1992; Myer, Lamkey, Walker, Brendemuhl, & Combs, 1992; Romans, Johnson, Wulf, Libal, & Costello, 1995a, 1995b; Shackleford et al., 1990). While decreasing the content of saturated fat in pork may provide a human health benefit, feeding diets high in mono- and poly unsaturates may have adverse affects on pork belly/ bacon quality (Shackelford et al., 1990; St. John et al., 1987). Utilizing traditional plant breeding techniques, high oil corn varieties with either high linoleic acid or high oleic acid/low polyunsaturated fatty acid profiles have been developed. The objective of this research was to characterize the effects of feeding these corn varieties with modified fatty acid content on belly/ bacon parameters.
0309-1740/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(02)00215-2
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Table 1 Phase 5 Finisher diet (all ingredients are shown as a percentage of the composition of the diet) Ingredient
CONV
CWG
HOC
HOHOC
Ground normal corn Ground high oil corn (HOC) Ground high oil, high oleic corn (HOHOC) Soybean meal (48%) Choice white grease Dicalcium phosphate Limestone Salt Swine vitamin mixa Swine mineral mixb l-Lysine HCL Antibiotic premixc
86.25 – – 11.35 – 0.840 0.650 0.500 0.150 0.100 0.100 0.025
79.785 – – 12.95 4.91 0.840 0.640 0.500 0.150 0.100 0.100 0.025
– 85.745 – 11.90 – 0.840 0.640 0.500 0.150 0.100 0.100 0.025
– – 85.27 11.90 – 0.840 0.640 0.500 0.150 0.100 0.100 0.025
a Supplied per kilogram of diet: vitamin A, 6600 IU; vitamin D3, 660 IU; vitamin E, 13.2 IU; vitamin K, 2.39 mg; vitamin B12, 0.018 mg; riboflavin, 4.95 mg; pantothenic acid, 16.83 mg; niacin, 19.80 mg. b Supplied mg/kg diet: Zn, 110; Fe, 110; Mn, 22; Cu, 11; I, 0.198; Se, 0.198. c Supplied mg/kg: bacitracin methylene disalicylate.
2. Materials and methods 2.1. Animals Crossbred barrows (EBGenepacker; n=196) were blocked by weight and randomly assigned to one of four treatments consisting of a control finishing diet containing normal corn and no added fat (CONV), normal corn and choice white grease (CWG), high-oil corn (HOC), and high-oil, genetically enhanced corn to be high in concentration of oleic acid (HOHOC). Pigs were fed a five-phase corn-soybean meal diet sequence, with a constant ratio of lysine to metabolizable energy (ME). Experimental diets were formulated based on the chemical analysis of the corn used. Both high oil corn were included in the diets at the same percentage, since they had similar (6.5%) fat content. An example of the phase 5 finisher diets are shown in Table 1. Fatty acid profiles of the corn sources can be found in Table 2. Pigs were arranged seven pigs per pen in 28 pens for a total of 49 pigs per treatment, and fed a five-phase corn-soybean meal diet sequence, where each diet had a constant ratio of lysine to metabolized energy. Experimental diets were Table 2 Fatty acid profiles of the various corn sources Fatty acid (%)
CONV
HOC
HOHOC
Palmitic, 16:0 Palmitoleic, 16:1 Stearic, 18:0 Oleic, 18:1 Linoleic, 18:2 Linolenic, 18:3
10.3 0.10 1.90 33.1 52.0 1.20
9.90 0.10 2.90 37.2 49.2 1.00
9.40 0.10 2.20 58.2 27.7 1.10
CONV=Conventional corn; HOC=high oil corn; HOHOC=high oleic, high oil corn.
formulated based on the chemical analysis of the corn used. Both high oil corns were included in the diets at the same percentage since they had similar fat contents (6.5%). Barrows had ad libitum access to feed and water and were fed to an average end weight of 118 kg. The University of Missouri Animal Care and Use Committee approved the production and research protocol. Following 98 d on test, two pigs representing the pen average (118 kg), were selected from each pen for humane slaughter at the University of Missouri abattoir (n=56). 2.2. Fresh belly fabrication and measurements Bellies were removed from the carcasses side and processed according to Institutional Meat Purchasing Specifications (IMPS #408; NAMP, 1997). Spareribs and related cartilage were removed, the bellies were squared (approximately 35.648.3 cm), and all remaining leaf fat removed. The fresh bellies with the skin on were evaluated by an objective flex test performed by centering the squared belly, fat side down, on a 7.6 cm diameter polyvinyl chloride (PVC) pipe mounted perpendicular to a board marked with a 2.54-cm grid matrix (Fig. 1). Lateral and vertical flex were determined from the degree of belly flex relative to the grid matrix. A lateral belly flex of zero meant the belly was completely parallel to the floor and was completely stiff. A vertical belly flex of 6 meant that the belly flexed to a point where there were 15.2 cm between the ends of the squared belly. Thus, a lower vertical and a higher lateral flex would indicate a firmer belly. Upon completion of the belly flex test, each squared belly was individually tagged with the appropriate identification, vacuum packaged, and frozen at 22 C for later processing.
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Fig. 1. Measuring lateral and vertical belly flex. (a) This illustrates a lower lateral, higher vertical flex; firmer belly. (b) This illustrates a higher lateral, lower vertical flex; softer belly.
2.3. Fatty acid profiles One slice was removed from the shoulder (cranial) end of the fresh belly slab and a 50-g sample of leaf (peritoneal) fat was collected from each belly, individually packaged, and frozen for transport to Dupont Specialty Grains (Des Moines, IA) for fatty acid profile analysis. Fatty acid analysis was performed using the modified method described by Park and Goins (1994), and Loor and Herbein (1998). In addition, the various corn samples utilized during the finishing period were analyzed with the same procedure as stated above. 2.4. Bacon processing and measurements Uncooked bellies were thawed (4 C) for 24 h and transported to a commercial packing plant where they were skinned, and weighed before (green weight) and after injection (pumped weight). The bellies were pumped fat side down using a Townsend multi-needle bacon injection pump (Townsend Inc., Des Monies, IA). A commercial brine (Excel Inc., Ottumwa, IA) was injected to 112% of the bellies green weight and allowed to drain to 110% of the green weight. The commercial brine consisted of 1.5% salt, 0.3% sugar, 0.3% sodium phosphate, 0.055% sodium erythorbate, 0.012% sodium nitrite. Bellies were hung by a bacon comb attached at the flank end and heat processed according to the plants commercial protocol. Following processing, bacon was removed from the smokehouse, showered for 10 min, drip dried for 10 min, and then chilled overnight at 3 C. The following morning, individual bacon slabs were weighed to determine smokehouse yield and placed in a tempering cooler (4 C) to facilitate optimal pressing and slicing. Full bacon slabs were pressed using a
commercial bacon press (Anco, Cherry-Burrell AMCA International Anco/Votator Division, Louisville, KY) and then sliced by a high-speed slicer at nine slices per 2.54 cm. The full sliced bacon drafts were placed on slip-sheets (complete with all ends and pieces) and placed in wax-coated boxes. Boxes were sealed and properly labeled for delivery to the University of Missouri Meat Science Laboratory. During high-speed slicing, it was necessary to use more than one slip-sheet to accommodate the entire bacon slab. During collection of the sliced bacon slabs, some partial slabs were placed in the boxes out of order. Therefore, 29 full bacon slabs were positively identified by matching lean and fat patterns within the bacon slices or on the exterior of the sparerib side of the slab. Slicing yield was the only processing variable affected by the mishandling. The number of bacon slabs remaining for analysis were as follows; CONV, n=7; CWG, n=7; HOC, n=6, and HOHOC, n=9. Slicing yield was determined by weighing (Fairbanks model H90–167–1, Fairbanks Scales, St. Johnsbury VT) the center portions of the bacon slab after the removal of comb marks and all incomplete slices. The remaining bacon slab, containing only commercially acceptable slices, was divided into five separate sections and labeled as, A, B, C, D, and E (Fig. 2; Mandigo, 1998). The first two slices from the cranial end were removed from each section and evaluated for fracture analysis. A trained person evaluated fracture analysis by rolling the bacon slice over the forefinger. A fracture was considered as lateral or vertical cracks in the structural integrity of the bacon slice. Subjective fracture analysis was performed by dividing the slice into four quadrants along the length of the bacon slice and assigning a score for each quadrant. The scores were then averaged for each slice. A score of
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Fig. 2. Sampling diagram for draft of sliced bacon.
0 indicated that no visual cracks or shattering could be detected, the scoring increased in severity with 2, 3, 4, 5, and a score of 6 being indicative of a ‘‘spider-web’’ consistency of shattering within the fat of the bacon slice (Mandigo, 1998). Five bacon slices per slab, representing one slice from each section (described earlier), were cooked (top and bottom plate=177 C; plate height=0.4 cm) on a MagiGrill PGB-60 (Magikich’n, Quackertown, PA) double belt conveyor cooker. Preliminary testing was conducted to verify the degree of doneness (golden brown; not crisp) and an automated setting for conveyor speed and upper and lower belt cooking temperatures. Cooked slice yield was targeted to be 40% of the original bacon slice weight. Each slice was weighed before and after cooking to the nearest 0.1 g (Ainsworth model CR-8101, Denver Instruments Co., Denver CO). After cooking, slices were allowed to cool for 10 min at room temperature on absorbent paper towels. Cooking loss was calculated as ((raw weightcooked weight)/raw weight)100. Bacon slice length was measured to the nearest 0.3 cm before and after cooking. Bacon slice cooking shrink (length change) was calculated as ((raw lengthcooked length)/raw length)100. Subjective evaluation of cooked slice visual distortion was evaluated using a 5-point distortion scale where 1 represented a mostly flat slice, and as severity of curling increased samples were rated 2, 3, 4, and 5 where 5 indicated a slice that completely curled with no flat areas on the slice (Fig. 3). 2.5. Statistical analysis The data was analyzed utilizing the Proc GLM procedure of SAS (SAS Institute, Cary, NC) and Least Square means were tested with the fixed effect of the treatments and then least square means tested for least significant differences. An alpha of P < 0.10 was considered a trend and a significant difference was set as an alpha of P < 0.05. Pearson correlation coefficients were calculated between fatty acid profiles, processing parameters, and belly quality (flex test).
Fig. 3. Numeric scale and examples for subjective visual evaluation of cooked bacon slice distortion.
3. Results and discussion 3.1. Fatty acid profile determination Several researchers have noted that the level of saturated fat in pork fat could be altered by the inclusion of unsaturated fat in the diet (Fontanillas et al., 1998; Larick et al., 1992; Leszczynski et al., 1992; Mazhar et al., 1990; Miller et al., 1990; Myer, Johnson et al., 1992; Myer, Lamkey et al., 1992; Romans et al., 1995a, 1995b; Shackleford et al., 1990). The fatty acid (FA) profile obtained from a slice taken from the fresh belly at 24 h postmortem differed across dietary treatments (Table 3). The total saturated fatty acids (SFA) decreased (P < 0.01) and total unsaturated fatty acids (UFA) increased (P < 0.05) with the addition of CWG, HOC, or HOHOC to the diet. The highest concentration of monounsaturated fatty acids (MUFA; P < 0.05) was found in the fat of pigs fed HOHOC, whereas the lowest concentration was found in the fat of pigs fed the CONV and HOC treatments. The increase in UFA and the decrease in SFA agree with other studies that have fed high oleic feedstuffs to pigs (Mazhar et al., 1990; Miller et al., 1990; Myer, Johnson et al., 1992; Myer, Lamkey et al., 1992; Shackelford et al., 1990). Past research has shown a decrease in SFA and an increase in MUFA and PUFA concentrations when diets were supplemented with oil seeds (sunflower, safflower, and canola) high in oleic acid (Miller et al., 1990; Myer, Lamkey et al., 1992), however, Myer, Lamkey et al. (1992) only noted a slight increase in MUFA concentration. In the current study, the highest concentration in
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G. Rentfrow et al. / Meat Science 64 (2003) 459–466 Table 3 Fatty acid LSMEANS and standard error for fresh bellies by treatment Fatty acid
Structure
CONV
CWG
HOC
HOHOC
SE
Significance
Capric Lauric Myristic Palmitic Palmitoleic Heptadecanoic Heptadecanoic Stearic Oleic Oleic Linoleic Linoleic Arachidic Eicosenoic Linolenic Eicosadienoic Eicosadienoic Eicosadienoic Arachidonic Docosatetraneoic CLA SFA UFA MUFA PUFA
C10:0 C12:0 C14:0 C16:0 C16:1 C17:0 cis10 C17:1 C18:0 C18:1trans C18:1cis C18:2trans C18:2cis C20:0 C20:1 C18:3 cis11, 14 C20:2 cis8, 11, 14 C20:3gamma cis11, 14, 17 C20:3 C20:4 C22:4
0.084ab 0.074 1.410 25.212b 2.722 0.363 0.333 12.627c 0.264b 44.228a 0.080a 9.046b 0.234b 0.813 0.343a 0.399b 0.075a 0.048a 0.223a 0.091a 0.145a 40.003b 58.664a 48.359a 10.306b
0.078a 0.074 1.388 24.057a 2.707 0.328 0.307 11.464b 0.292c 45.666b 0.107b 9.814c 0.186a 0.805 0.386b 0.430b 0.083b 0.054b 0.262b 0.103b 0.164b 37.574a 61.016bc 49.778b 11.238c
0.088b 0.078 1.426 24.024a 2.716 0.328 0.283 10.601a 0.222a 43.752a 0.080a 12.871d 0.220ab 0.728 0.353a 0.496c 0.087b 0.043a 0.273b 0.114c 0.144a 36.764a 62.018c 47.701a 14.317d
0.084b 0.079 1.486 24.583ab 2.758 0.338 0.304 10.922ab 0.250b 47.438c 0.084a 8.197a 0.202ab 0.831 0.359a 0.326a 0.069a 0.045a 0.226a 0.088a 0.141a 37.694a 60.975b 51.581c 9.395a
0.002 0.002 0.130 0.236 0.084 0.020 0.019 0.208 0.007 0.350 0.006 0.270 0.012 0.028 0.008 0.015 0.003 0.002 0.009 0.003 0.005 0.376 0.368 0.376 0.300
P< 0.05 NS NS P< 0.01 NS NS NS P< 0.01 P< 0.01 P< 0.01 P< 0.01 P< 0.05 P< 0.01 NS P< 0.05 P< 0.01 P< 0.05 P< 0.05 P< 0.01 P< 0.05 P< 0.01 P< 0.01 P< 0.05 P< 0.05 P< 0.05
Means within a row with different letters differ significantly. CONV=Conventional corn; CWG=Choice white grease; HOC=High oil corn; HOHOC=High oil, high oleic corn; CLA=Conjugated linoleic acid; SFA=Saturated fatty acids; UFA=Unsaturated fatty acids; MUFA= Monounsaturated fatty acids; PUFA=Polyunsaturated fatty acids.
MUFA occurred in the pigs fed HOHOC. The HOC treatment possessed the highest concentration of UFA in this study and tended to have the highest slicing yield (exhibiting a trend at P< 0.10; Table 4). The pigs fed CONV possessed the highest percentage of SFA and the lowest USF concentration, and had the lowest vertical (a lower vertical flex=a firmer belly) and highest lateral flex test (a higher lateral flex=a firmer belly). Likewise, the HOC fed pigs had bellies with the highest percentage of UFA and the highest vertical and lowest lateral flex (Table 5). Which would indicate a ‘‘softer’’ belly; however, the softer belly did not result in poorer slice-ability. According to Pork Composition and Quality Assessment Procedures (NPPC, 2000), quality pork fat must have < 15% polyunsaturated fatty acids (PUFA) and > 15% stearic acid (18:0). Furthermore, pork fat containing > 14% linolenic acid (C18:2) is associated with soft fat. In the present study, HOC approached the 15% limit for PUFA (14.32%; Table 3). None of the dietary treatments resulted in deposition of > 15% stearic acid and none contain > 14% linolenic acid. The results of this study would suggest that even though dietary fatty acid profile was altered, an acceptable FA composition was achieved across each treatment group resulting in adequate belly firmness and, subsequently, acceptable slice-ability.
Correlation coefficients between selected FA concentration and fresh belly and bacon parameters are reported in Table 6. Significant correlations were seen between PUFA and lateral and vertical belly flex (r=0.3906 and 0.4773, respectively) and shatter score (r=0.5835). In this study, the saturated fat palmitic acid was more highly correlated with lateral (r=0.5000) and vertical (r=0.4705) belly flex than was stearic acid. Palmitic acid also had a significant (P=0.02) positive correlation (r=0.3384) with shatter score, suggesting that evidence of shattering increases as the percentage of palmitic acid increases. Significant correlations were seen between linolenic acid (C18:2) and lateral (r=0.3810) and vertical (r=0.4713) belly flex and shatter score (r=0.5844). Mazhar et al. (1990) and Shackleford et al. (1990) noted that the addition of canola (ground or oil) to the diet produced softer bacon, as evaluated by a trained sensory panel. In addition, Miller et al. (1990) found that pig diets supplemented with high oleic oil seeds (sunflower, safflower, and canola oils) had softer, oilier fat than controls. Furthermore, Myer, Johnson et al. (1992) and Myer, Lamkey et al. (1992) found that pigs fed high oil peanuts and/or canola oil had softer fat, than their unsupplemented counterparts. A primary focus of this study was to evaluate genetically enhanced high oleic, high oil corn. Table 3 shows
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Table 4 Least squares means and standard errors for slicing yield of bacon slabs after high-speed slicing Variable a
Number of bacon slabs used in evaluation High-speed slicing yieldb(%)
CONV
CWG
HOC
HOHOC
SE
Significance
7 78.24ab
7 70.27a
6 84.07b
9 70.12a
4.90
P< 0.10
Means within a row with different letters differ significantly. a Slicing yield evaluated on full center section bacon slabs positively identified at the Excel packing plant. b Slicing yield=(weight of intact, full-length center slices/cooked pressed weight)100.
LSMEANS indicating that the HOHOC treatment resulted in a significantly higher concentration of oleic acid in the fat tissue of the fresh pork belly. These results are in agreement with other studies that showed an increase in oleic acid deposited in fat tissue when diets were supplemented with oils high in oleic acid concentrations (Miller et al., 1990; Myer, Johnson et al. 1992; Shackelford et al., 1990). Oleic acid (C18:1 cis) concentrations had no significant correlation with any of the processing parameters reported in Table 6, however, a significant (P=0.038) negative correlation (r=0.3877) was observed for slicing yield (Table 6), indicating that as the concentration of C18:1 cis increased, slicing yield decreased. The variant C18:1 trans was significantly (P=0.049) correlated only to shatter score (r=0.2888). Shackelford et al. (1990) indicated an increased concentration of oleic acid (18:1) in pork fat noting a decrease in bacon slicing yields as a result of supplementing canola oil, which is in agreement with this study.
3.2. Processing and cooking yields No differences were observed across treatments for green weight, pumped weight, pressed center weight, or smokehouse yield (Table 5). Furthermore, no differences were observed across dietary treatments for the cooked bacon parameters of cooking loss, cooked length shrink, or visual distortion score (Table 5). It can be concluded that dietary treatment had no affect on the yield of fresh pork belly, yield of processed un-sliced bacon, or cooking yield. Pigs fed HOC had lower bacon slice fracture scores (P < 0.01), however no differences were observed between the other dietary treatments (Table 5). These data coincide with findings of Shackelford et al. (1990) in which pump yield and overall yield of bellies/bacon were not affected by supplementing pig diets with animal fat, sunflower oil, safflower oil, or canola oil. However, Shackelford et al. (1990) did find that dietary treatments produced higher cooking yields than controls, and the addition of canola oil lowered
Table 5 Least squares means and standard errors for bacon processing Variable a
Fresh belly, Vertical flex (inches) Fresh belly, Lateral flex (inches)b Green weight (pre-pump) (lbs.) Pump percentagec (%) Cooked pressed center weight (lbs.) Smokehouse yieldd (%) Shattere Bacon slice cooking lossf (%) Bacon slice cooking shrinkg (%) Cooked bacon slice visual scoreh
CONV
CWG
HOC
HOHOC
SE
Significance
14.14a 10.21c 8.31 13.98 6.87 88.54 3.46b 58.00 29.75 2.18
16.13b 8.32ab 8.90 13.42 7.11 90.21 3.44b 60.04 31.39 2.36
16.00b 7.71a 8.60 13.37 7.65 91.59 2.55a 57.89 30.38 2.21
15.42b 8.89abc 8.85 13.82 7.00 91.14 3.46b 57.46 31.14 2.27
0.459 0.535 0.250 0.269 0.635 1.398 0.243 1.13 1.19 0.121
P< 0.05 P< 0.05 NS NS NS NS P< 0.01 NS NS NS
Means within a row with different letters differ significantly. a Recorded as the summation of vertical flex from right and left ends of loin or belly whereby zero flex would be flat; a vertical flex reading of ‘‘800 would be equivalent to the left side of the loin/belly flexing to a point of 4-inches on the left and 4-inches on the right. A lower vertical flex would be a firmer loin/belly. b Recorded as the summation of lateral flex from right and left ends of loin or belly whereby a zero lateral flex would be a complete folding of the loin/belly; a lateral flex reading of ‘‘800 would be equivalent to 8 inches separating the opposing ends. A higher lateral flex would be a firmer loin/ belly. c Pump percentage=((pumped belly weightgreen weight)/green belly weight)100. d Smokehouse yield=(Cooked pressed center weight/pumped weight)100. e Subjective evaluation of slice integrity (fracture) from 0 to 6 where 0=intact slice possessing no shatter and 6=‘‘spider-web’’ fracture. f Bacon slice cooking loss=((raw weightcooked weight)/raw weight)100. g Bacon slice cooking shrink=((raw lengthcooked length)/raw length)100. h Subjective evaluation of slice appearance (curling, cooked distortion) from 0 to 6 where 0=flat slice with no distortion and 6=extreme curling and distortion.
(0.5099) (0.7571) (0.3373) (0.1153) (0.3621) (0.5278) (0.0758) (0.8178) (0.5186) (0.2196) (0.5649) 0.0964 0.0453 0.1400 0.2279 0.1331 0.0924 0.2560 0.0338 0.0944 0.1786 0.0843 (0.1657) (0.4583) (0.1528) (0.2603) (0.0833) (0.8825) (0.0719) (0.7945) (0.5046) (0.4792) (0.9378) 0.1991 0.1073 0.2052 0.1622 0.2474 0.0214 0.2567 0.0378 0.0966 0.1024 0.0113 (0.7033) (0.4299) (0.5537) (0.4188) (0.0173) (0.3937) (0.5283) (0.7971) (0.7687) (0.5581) (0.4405) 0.0552 0.1142 0.0858 0.1169 0.3354 0.1233 0.0913 0.0373 0.0427 0.0848 0.1116 0.3384 0.2761 0.2888 0.2412 0.0382 0.5844 0.2093 0.3751 0.4389 0.2499 0.5835 Palmitic acid (C16:0) Stearic acid (C18:0) Oleic acid (C18:1 trans) Oleic acid (C18:1 cis) Linoleic acid (C18:2 trans) Linoleic acid (C18:2 cis) CLA SFA UFA MUFA PUFA
0.5000 0.3662 0.1263 0.0120 0.1436 0.3810 0.1341 0.4923 0.4417 0.0115 0.3906
(0.0001) (0.0047) (0.3446) (0.9286) (0.2823) (0.0032) (0.3155) (0.0001) (0.0005) (0.9315) (0.0024)
0.4705 0.3510 0.1219 0.0202 0.1118 0.4713 0.1390 0.4712 0.5018 0.0495 0.4773
(0.0002) (0.0069) (0.3618) (0.8804) (0.4032) (0.0002) (0.2980) (0.0002) (0.0001) (0.7122) (0.0002)
0.2678 0.0411 0.0401 0.2151 0.1704 0.0236 0.2494 0.1405 0.1992 0.1924 0.0116
(0.0550) (0.7723) (0.7777) (0.1256) (0.2272) (0.8681) (0.0746) (0.3205) (0.1569) (0.1717) (0.9348)
0.0369 0.0971 0.0615 0.1152 0.2442 0.0138 0.0253 0.0788 0.0771 0.0898 0.0183
(0.7949) (0.4934) (0.6650) (0.4160) (0.0810) (0.9228) (0.8585) (0.5785) (0.5872) (0.5267) (0.8976)
0.0367 0.0522 0.0531 0.1232 0.0124 0.1861 0.0404 0.0664 0.0747 0.1418 0.1891
(0.8155) (0.7394) (0.7355) (0.4311) (0.9370) (0.2322) (0.7969) (0.6721) (0.6340) (0.3645) (0.2245)
0.0635 0.1123 0.2023 0.3877 0.0503 0.2845 0.1985 0.0398 0.0273 0.3348 0.2772
(0.7434) (0.5618) (0.2926) (0.0377) (0.7955) (0.1347) (0.3019) (0.8377) (0.8882) (0.0758) (0.1455)
Shatter score Slicing yield Smoked center bacon slab weight Smokehouse yield Pumping percent Fresh belly, lateral flex Fresh belly, vertical flex
Table 6 Pearson correlation coefficients (and probability>|R| under Ho) between select bacon processing parameters and fatty acid content
(0.0200) (0.0603) (0.0490) (0.1024) (0.7989) (0.0001) (0.1580) (0.0094) (0.0020) (0.0903) (0.0001)
Cooked, weight loss
Cooked slice shrinkage
Cooked, visual score
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slicing yields. These observations were not seen in the present study. Mazhar et al. (1990) added ground canola seed to the diet and noted that green weight yield, smokehouse yield, and cooking yield were not affected by treatment; this is consistent with the present study. Canola seed/oil, sunflower oil and safflower oil are all high in oleic acid, which makes these studies a notable comparison to feeding high oleic corn.
4. Conclusions The results of this study indicate that the fatty acid profile of the diet, as influenced by corn type, had no effect on green weight, pumped weight, smokehouse yield, or pressed center weight. In addition, there were no differed for the cooked bacon slice parameters of cooking loss, cooked length shrink, or visual distortion score. However, dietary treatment influenced pork fatty acid profile, with the highest concentration of saturated fatty acids in pork from pigs fed the conventional corn and the highest concentration of total unsaturated fatty acids in pork form pigs fed the high oil corn diets. Even though the dietary treatments produced softer bellies compared to the conventional corn treatment, there were no adverse effects to belly/bacon quality parameters.
Acknowledgements The authors would like to thank DuPont Specialty Grains for assistance with this research project. In addition, the authors would like to thank Dr. Doug Sutton, the Excel Corporation, Dr. Mike Linville, Chad Stahl, and Kasey Maddock for their help throughout this project.
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