J. W. S. Yancey

Cookery method and end-point temperature can affect the Warner–Bratzler shear force, cooking loss, and internal cooked color of beef longissimus steaks

Steaks from 60 beef ribeye rolls were used to test the interactive effects of cookery method and end-point temperature on Warner-Bratzler shear force (WBSF) and internal cooked color. Pairs of longissimus thoracis (LT) steaks were assigned to combinations of 3 different end-point temperatures and 5 cookery methods. The forced-air convection oven (FAC) required the longest time and produced the reddest internal color, regardless of end-point temperature. The clam-shell grill (CLAM) required the least cooking time and resulted in the lowest cooking losses, but CLAM-cooked steaks also had the greatest WBSF values and least red internal color. Repeatability values for WBSF were acceptable (>0.60) for all degrees of doneness when steaks were cooked in the FAC and impingement oven, but steaks cooked on the CLAM were not repeatable. The relationship of myofibrillar toughening, moisture loss and cooked color changes in beef LT steaks also differed due to cookery methods.

Interactive effects of dietary fat source and slaughter weight in growing-finishing swine: II. Fatty acid composition of subcutaneous fat.

Crossbred pigs (n=288) were used to test the interactive effects of dietary fat source and slaughter weight on the fatty acid composition of subcutaneous fat. Pigs were blocked by initial BW (28.1 kg), and, within blocks, pens (8 pigs/pen) were randomly assigned to either grower and finisher diets devoid of added fat (Ctrl) or diets formulated with 5% beef tallow (BT), poultry fat (PF), or soybean oil (SBO). Immediately after treatment allotment, as well as at mean block BW of 45.5, 68.1, 90.9, and 113.6 kg, 1 pig was randomly selected from each pen, slaughtered, and, within 1 h postmortem, samples of backfat were removed from each carcass between the 4th and 8th thoracic vertebra and separated into the inner, middle, and outer layers for fatty acid composition analysis. During the first 17.4 kg of BW gain, percentages of all SFA increased by more than 4% in subcutaneous fat of pigs fed the Ctrl and BT diets, but decreased by 4.4 and 7.7% in pigs fed the PF and SBO diets, respectively (fat source x slaughter weight, P<0.001). Proportions of all MUFA in subcutaneous fat from BT-fed pigs increased by 6.1% during the first 17.4 kg of BW gain, but MUFA percentages in SBO-fed pigs decreased by 9.1% between 28.1 and 45.5 kg (fat source x slaughter weight, P<0.001). Conversely, percentages of all PUFA from SBO-fed pigs increased by 39.9%, whereas PUFA concentrations in BT-fed pigs decreased by 12.6% as slaughter weight increased from 28.1 to 45.5 kg (fat source x slaughter weight, P<0.001). Resultant iodine values (IV) of subcutaneous fat from SBO-fed pigs increased (P<0.05) from 73.5 to 85.2 within the first 17.4 kg of BW gain, and remained elevated above those of their contemporaries fed the Ctrl, BT, or PF diets at each subsequent slaughter weight (fat source x slaughter weight, P<0.001). The inner backfat layer had the greatest (P<0.05) proportions of all SFA and the least (P<0.05) proportions of all PUFA, whereas the outer layer had the least (P<0.05) percentages of all SFA but the greatest (P<0.05) percentages of all MUFA. Even though the middle and outer subcutaneous fat layers had similar (P>0.05) PUFA percentages, the greatest (P<0.05) and least (P<0.05) IV were in the outer and middle layers, respectively. As expected, the fat source included in swine diets was responsible for the fatty acid compositional changes in subcutaneous fat, yet the results of this study indicate that feeding 5% SBO dramatically increased the polyunsaturation of subcutaneous fat within the first 17.4 kg of BW gain, with backfat IV exceeding 80 thereafter.

Interactive effects of dietary fat source and slaughter weight in growing-finishing swine: III. Carcass and fatty acid compositions

Crossbred pigs (n=288) were used to test the interactive effects of dietary fat source and slaughter weight on dissected carcass composition and fatty acid composition of composite carcass samples. Pigs were blocked by initial BW, and within each of 9 blocks, pens (8 pigs/pen) were randomly assigned to either control corn-soybean meal grower and finisher diets (Ctrl) or diets formulated with 5% beef tallow (BT), poultry fat (PF), or soybean oil (SBO). Immediately after treatment allotment, as well as at mean block BW of 45.5, 68.1, 90.9, and 113.6 kg, 1 pig was randomly selected from each pen and slaughtered, and primal cuts from right carcass sides were dissected into muscle, fat, bone, and skin components. Muscle and fat tissues were then ground, and random composite samples were collected from each carcass for fatty acid composition analysis. Fat source did not alter pork primal cut yields (P >or= 0.294), nor were the percentages of carcass muscle (P=0.213), fat (P=0.502), and bone (P=0.551) affected by dietary fat source. Conversely, percentages of the whole shoulder and ham decreased linearly (P<0.001), and the percentages of loin and belly increased (P<0.001) linearly with increasing slaughter weight. Moreover, linear decreases (P<0.001) in carcass muscle, bone, and skin, as well as a linear increase (P<0.05) in carcass fat, were observed as slaughter weight increased from 28.1 to 113.6 kg. Composite samples from pigs fed the BT or Ctrl diets had greater (P<0.05) proportions of SFA, particularly oleic and stearic acids, than those from pigs fed the PF and SBO diets when slaughtered at 45.5, 68.1, and 90.9 kg (fat source x slaughter weight, P<0.001). Percentages of MUFA (including palmitoleic, oleic, and cis-vaccenic acids) decreased (P<0.05), and percentages of all PUFA, especially linoleic and linolenic acids, and iodine values increased (P<0.05) in samples from SBO-fed pigs as slaughter weight increased from 28.1 to 113.6 kg (fat source x slaughter weight, P<0.001). Dietary fat source did not affect carcass composition; however, including 5% SBO in swine diets increased the polyunsaturation of pork, which could lead to economic ramifications associated with soft pork and pork fat.

Consumer responses for tenderness and overall impression can be predicted by visible and near-infrared spectroscopy, Meullenet-Owens razor shear, and Warner-Bratzler shear force.

Beef ribeye rolls (n=40) from Select, low Choice, top (upper 2/3) Choice, and Prime quality grade carcasses were used to determine the relationship of visible and near-infrared spectroscopy (VNIR) reflectance, Warner-Bratzler shear force (WBSF), and Meullenet-Owens razor shear (MORS) with consumer responses for tenderness and overall impression. Steaks (2.54 cm) were cut and assigned to either 14 or 28d aging (n=4/aging period). Reflectance in the VNIR spectrum was measured 1d from the box-date no less than 30 min after cutting, and prior to aging. The steak used for VNIR measurement was designated for WBSF and MORS measurement, whereas three adjacent steaks were cooked for evaluation by a consumer panel (n=240 members). Steaks from the Select-grade ribeye rolls had the greatest (P=0.06) WBSF values and lower (P<0.05) overall impression scores than those from top Choice and Prime quality grades. Consumer panelists evaluated steaks aged 28 d as more tender (P<0.05) than those aged 14 d. The relationship of mechanical tenderness measurements were higher with consumer panel responses for tenderness than with overall impression, and those relationships were stronger for the Select grade than for quality grades with higher degrees of marbling. The 2nd derivatives of VNIR measurements were more successful at predicting consumer panel responses of tenderness and overall impression than WBSF and MORS; thus, VNIR methodology was less invasive and more predictive than other, more traditional tenderness measurements.

Fresh and cooked color of dark-cutting beef can be altered by post-rigor enhancement with lactic acid.

Fresh and cooked color of dark-cutting (DC) beef strip loins (mean pH=6.56) enhanced with 0.25, 0.50, 0.75 or 1.00% lactic acid (LA) were compared to non-enhanced DC and normal pH (NpH; mean pH=5.43) strip loins. Even though NpH steaks received the most (P<0.05) desirable fresh color scores, color scores for steaks from DC sections enhanced with 0.25% LA approached those of NpH steaks after the first day of retail display. Discoloration scores were also similar (P>0.05) among NpH and 0.25% LA-enhanced DC steaks throughout the 5 d of display. Fresh steaks from NpH strip loins were redder, as evidenced by greater (P<0.05) a(∗) values and lower (P<0.05) hue angles, than DC steaks and DC steaks enhanced with LA, regardless of concentration. However, cooked color scores and proportions of denatured myoglobin were similar (P>0.05) between untreated NpH steaks and DC steaks enhanced with 0.25% LA. Results from this study indicate that enhancing DC beef with LA may lead to the brightening of the fresh color and prevention of the persistent red cooked color, approaching that of NpH beef.

Influence of vacuum-aging period on bloom development of the beef gluteus medius from top sirloin butts

The gluteus medius (GM) from USDA Select beef carcasses was used to test the effect of aging period on bloom development. Top sirloin butts (IMPS #184) were randomly allocated to 0, 7, 14, 21, 28, and 35d vacuum-aging at 2°C (n=10/aging period). Each week, aged top sirloin butts were faced before two 2.5-cm-thick, non-adjacent steaks were cut and instrumental color (L(∗), a(∗), and b(∗)) of the GM was measured at 10-min intervals for 2h after cutting. Steaks aged for 7 and 14d were a more vivid (greater chroma values; P<0.05), redder (greater a(∗) values; P<0.05), and more yellow (greater b(∗) values; P<0.05) color than steaks from the other aging periods. Change in total color (ΔE) was greater (P<0.05) for steaks from top sirloin butts aged 7, 14, and 21d than steaks from top butts aged 28 and 35d, whereas oxymyoglobin percentages for steaks from top butts aged 7 and 14 days were greater (P<0.05) than those from top sirloin butts aged 28 and 35d. As much as 90% of the total increase (P<0.05) in a(∗), b(∗), and chroma values, as well as hue angles and oxymyoglobin percentages, was achieved during the first 60min after cutting.

Lactic acid enhancement can improve the fresh and cooked color of dark-cutting beef12

Two experiments were conducted to compare the effects of enhancing dark-cutting (DC) strip loins with lactic acid (LAC) on fresh and cooked beef color, as well as sensory attributes, with nonenhanced, normal pH strip loins (CH). Strip loins, with an average ultimate pH of 6.70 ± 0.11 (Exp. 1) and 6.78 ± 0.11 (Exp. 2), were cut into 2 equal-length sections, and DC sections were randomly assigned as either nonenhanced DC or DC enhanced with 0.15 (Exp. 1), 0.35 (Exp. 1 and 2), or 0.50% (Exp. 2) LAC at a target of either 105 (Exp. 1) or 112% (Exp. 2) of the raw product weight. Enhancement with 0.15 and 0.35% LAC did not (P > 0.05) affect postenhancement pH of DC strip loins when enhanced at a target of 105% (Exp. 1); however, postenhancement pH was reduced (P < 0.05) substantially by LAC enhancement at 115% of raw product weight, with pH values of DC sections enhanced with 0.50% LAC being similar (P > 0.05) to those of CH strip loin sections (Exp. 2). In Exp. 1, raw steaks from CH strip loins had greater (P < 0.05) a* and b* values as well as Japanese beef color scores compared with steaks from nonenhanced and LAC-enhanced DC strip loins across the first 3 d of simulated retail display (LAC enhancement × retail display duration; P < 0.01). Again in Exp. 2, raw steaks from CH sections had greater (P < 0.05) L*, a*, and b* values and Japanese color scores than did steaks from DC sections, regardless of LAC enhancement; however, mean Japanese color scores of CH steaks were only 0.7 and 0.4 units greater (P < 0.05) than the color scores of DC steaks enhanced with 0.35 and 0.50% LAC, respectively. In Exp. 1, CH steaks received the highest (P < 0.05) cooked color and degree of doneness scores, yet scores for CH steaks and steaks from DC sections enhanced with 0.50% LAC did not (P > 0.05) differ when cooked to 71°C in Exp. 2. Fresh and cooked color of DC beef was only minimally altered when enhanced with 0.35% LAC at 105% of the fresh product weight; however, when DC beef was enhanced with 0.35 and 0.50% LAC at a target of 112%, fresh and cooked color were improved close to that of CH beef. Because the persistent red or pink cooked color of DC was virtually eliminated by 0.50% LAC enhancement, LAC-enhanced DC beef may be suitable for food-service markets; however, the raw or fresh color results of Exp. 2 suggested that the fresh color of DC beef can be improved to the color of normal pH beef by postmortem acidification, leading to the possible recoupment of most, if not all, of the lost value associated with DC beef.

Effects of l-carnitine supplementation on quality characteristics of fresh pork bellies from pigs fed 3 levels of corn oil1

Crossbred pigs (n = 216) were used to test the effect of supplemental L-carnitine (CARN) on the fatty acid composition and quality characteristics of fresh pork bellies from pigs fed diets formulated with different inclusion levels of corn oil. Pigs were blocked by BW (43.6 ± 1.0 kg) and allotted randomly to pens of 6 pigs within blocks. Then, within blocks, pens were assigned randomly to 1 of 6 dietary treatments in a 2 × 3 factorial arrangement, with either 0 or 100 mg/kg of supplemental CARN and 3 dietary inclusion levels (0, 2, or 4%) of corn oil (CO). When the lightest block weighed 125.0 kg, all pigs were slaughtered, and left-side bellies were captured during carcass fabrication for quality data collection. Fresh pork bellies were evaluated for length, width, thickness, and firmness (bar-suspension and Instron-compression methods) before a 2.5-cm-wide strip of belly was removed and subsequently dissected into subcutaneous fat, primary lean (latissimus dorsi), secondary lean (cutaneous trunci), and intermuscular fat for fatty acid composition determination. Although belly length, width, and thickness of fresh pork bellies were not affected by CARN (P ≥ 0.128) or CO (P ≥ 0.073), belly firmness decreased linearly (P < 0.001) with increasing dietary CO, but there was no (P ≥ 0.137) effect of CARN on any belly firmness measure. Dietary CARN increased (P < 0.05) the proportion of total SFA in the intermuscular fat layer, increased (P < 0.05) the proportion of total MUFA in the primary and secondary lean layers, and decreased (P < 0.05) the proportion of total PUFA in the intermuscular fat and secondary lean layers of pork bellies. Moreover, the SFA and MUFA compositions decreased linearly (P < 0.001) with increasing dietary CO, and the rate of the decrease in SFA composition was greater (P < 0.001) in the fat layers than the lean layers. Conversely, the PUFA content increased linearly (P < 0.001) with increasing dietary CO, and the rate of the increase in PUFA was greater (P < 0.001) in the fat than the lean layers, and greater (P = 0.022) in the primary than secondary lean layer. Results from this study would indicate that differences in the amount and rate of fatty acid deposition associated with feeding increased amounts of CO, along with moisture differences among the belly layers, combine to negatively affect fresh pork belly firmness.

Influence of wet-aging on bloom development in the longissimus thoracis.

The longissimus thoracis (LT) from USDA Select beef carcasses was used to test the effect of aging period (0, 7, 14, 21, 28, or 35d) on bloom development (n=10/aging period). After aging, two 2.54-cm-thick, non-adjacent steaks were cut and instrumental color of the LT was measured at 10-min intervals for 2h. All instrumental color parameters increased (P<0.05) over 40% during the first 10min; however, asymptotic points indicated that color plateaued sometime after 120min. Although aging did not (P⩾0.05) affect the values where color development plateaued, rate of oxymyoglobin formation tended to be the slowest (P=0.06) in LT steaks aged 7d compared to steaks aged 0, 14, 28 and 35d. Results indicated that as much as 90% of the total increase (P<0.05) in instrumental color and oxymyoglobin percentages was achieved during the first 60min after cutting, but aging period had no impact on bloom development.

Noni puree (Morinda citrifolia) mixed in beef patties enhanced color stability

Ground beef, mixed with 0, 2, 4, and 6% Noni puree, was formed into 150-g patties, aerobically packaged, and displayed in retail for 5d. After 2 and 3d, patties with higher concentrations of Noni were perceived as redder and less discolored (P<0.05) by visual panelists. Noni patties were found to have greater (P<0.05) a* values than controls, even though all patties became less red during display. After 3 and 5d of retail display, patties with higher concentrations of Noni puree also had lower TBARS (were less oxidized; P<0.05). In fresh taste panels, panelists perceived the patties to have less beef flavor and greater incidence of off-flavors (P<0.05) as Noni puree concentration increased. The potential of Noni puree to improve the color stability and shelf life of fresh ground beef is very promising, but the flavors produced by the addition of Noni in ground beef may be detrimental to its use.