J.T. Keeton

Low-fat meat products-technological problems with processing.

Diet and health advice serve as a driving force to redirect the types of foods considered to be most beneficial in terms of improved health and quality of life for Americans. Although meat cuts have become leaner, products such as ground beef, fresh pork sausage, coarse ground sausages and emulsified sausages traditionally have higher levels of fat. However, these products offer the greatest opportunity for fat reduction by reformulation with fat substitutes. Fat replacements should contribute a minimum of calories to a product and should not be detrimental to organoleptic qualities. Most substitutes can be categorized as: leaner meats, added water, protein-based substitutes, carbohydrate-based substitutes and synthetic compounds, Reducing the fat content to ∼10% often results in cooked ground beef that is bland and dry with a hard, rubbery or mealy texture. Reformulation with fat substitutes can cause a reduction in particle binding, darker product color, lack of beef flavor, reduced browning reactions and shorter microbiological shelf-life. Other problems that occur with low-fat (5-10%) fresh or cooked/smoked sausages are reduced cook yields, soft mushy interiors, rubbery skin formation, excessive purge in vacuum packages, shorter shelf-life and changes in sensory qualities after cooking or reheating. However, some combinations of fat replacements that mimic the mouthfeel and textural characteristics of fat offer potential for development of low-fat meat products.

Utilization of soy protein isolate and konjac blends in a low-fat bologna (model system)

Low-fat bologna formulations (LFBMS, <2.0% fat) were manufactured in a model system with two levels (0.5 or 1%) of two konjac blends (KB; KSS=konjac flour/starch and KNC=konjac flour/carrageenan/starch), and three levels (0, 2.2, 4.4%, DWB) of prehydrated soy protein isolate (SPI) to replace 0, 2 and 4% of the meat protein, respectively. Compared to 0.5% KB, the 1% level reduced (p<0.05) protein solubility (PS), vacuum purge (VP, %) and texture profile analysis (TPA) hardness. LFBMS containing KNC had higher (p<0.05) cooking yields, TPA fracturability and shear stress, but lower (p<0.05) expressible moisture (EM), VP values and TPA cohesiveness than KSS. Replacement of 4% meat protein with SPI increased (p<0.05) pH and yellowness (b*), but decreased (p<0.05) redness (a*), PS, EM and most textural characteristics, whereas no differences (p>0.05) were observed between 0 and 2% of meat protein replacements with SPI for most characteristics.

Inhibition of Listeria monocytogenes by Food Antimicrobials Applied Singly and in Combination

Combining food antimicrobials can enhance inhibition of Listeria monocytogenes in ready-to-eat (RTE) meats. A broth dilution assay was used to compare the inhibition of L. monocytogenes resulting from exposure to nisin, acidic calcium sulfate, ε-poly-L-lysine, and lauric arginate ester applied singly and in combination. Minimum inhibitory concentrations (MICs) were the lowest concentrations of single antimicrobials producing inhibition following 24 h incubation at 35 °C. Minimum bactericidal concentrations (MBCs) were the lowest concentrations that decreased populations by ≥3.0 log(10) CFU/mL. Combinations of nisin with acidic calcium sulfate, nisin with lauric arginate ester, and ɛ-poly-L-lysine with acidic calcium sulfate were prepared using a checkerboard assay to determine optimal inhibitory combinations (OICs). Fractional inhibitory concentrations (FICs) were calculated from OICs and were used to create FIC indices (FIC(I)s) and isobolograms to classify combinations as synergistic (FIC(I) < 1.00), additive/indifferent (FIC(I)= 1.00), or antagonistic (FIC(I) > 1.00). MIC values for nisin ranged from 3.13 to 6.25 μg/g with MBC values at 6.25 μg/g for all strains except for Natl. Animal Disease Center (NADC) 2045. MIC values for ε-poly-L-lysine ranged from 6.25 to 12.50 μg/g with MBCs from 12.50 to 25.00 μg/g. Lauric arginate ester at 12.50 μg/g was the MIC and MBC for all strains; 12.50 mL/L was the MIC and MBC for acidic calcium sulfate. Combining nisin with acidic calcium sulfate synergistically inhibited L. monocytogenes; nisin with lauric arginate ester produced additive-type inhibition, while ε-poly-L-lysine with acidic calcium sulfate produced antagonistic-type inhibition. Applying nisin along with acidic calcium sulfate should be further investigated for efficacy on RTE meat surfaces.

Antioxidant Properties of Dried Plum Ingredients in Raw and Precooked Pork Sausage

Raw pork sausages with no antioxidant (control), 3% or 6% dried plum puree (DP), 3% or 6% dried plum and apple puree (DPA), or 0.02% butylated hydroxytoluene and butylated hydroxyanisole (BHA/BHT) were (1) stored raw in chubs at 4 degrees C (RR) and evaluated weekly over 28 d, (2) cooked as patties, vacuum packaged, and stored at 4 degrees C (PR) for weekly evaluation over 28 d, or (3) cooked, vacuum packaged, and stored at -20 degrees C (PF) and evaluated monthly over 90 d. DP at 3% or 6% levels was as effective as BHA/BHT for retarding lipid oxidation in PR sausage patties. Likewise, DP at 3% was equally as effective in PF patties, but DP at 6% was even more effective (lower TBARS values) than BHA/BHT for retarding oxidative rancidity. All treatments decreased the fat and increased moisture content of raw sausages but only 6% DP reduced cooking yields. Inclusion of 6% DP decreased internal redness while both 6% DP and DPA increased yellowness of raw sausage. Trained panel sensory evaluations indicated that DP enhanced sweet taste, decreased salt and bitter tastes, and masked cooked pork/brothy, cooked pork fat, spicy/peppery, and sage flavors. In general, warmed-over flavor notes were not affected by storage treatments. Overall, pork sausage with 3% DP or DPA was as acceptable to consumers as the control or those patties with BHA/BHT, but patties with 6% of either plum product were less desirable. Inclusion of 3% DP was effective as a natural antioxidant for suppressing lipid oxidation in precooked pork sausage patties.

Antioxidant properties of plum concentrates and powder in precooked roast beef to reduce lipid oxidation

Boneless beef roasts (Semimembranosus+Adductor) were injected (20%) with a brine containing (1) no plum ingredient (control), (2) 2.5 or 5% fresh plum juice concentrate (FP), (3) 2.5 or 5% dried plum juice concentrate (DP), or (4) 2.5 or 5% spray dried plum powder (PP). Whole roasts were cooked, vacuum-packaged and stored at <4.0°C for 10wk. At 2wk intervals, evaluations were performed on sliced product to determine vacuum-packaged purge, Allo-Kramer shear force, lipid oxidation (TBARS), color space values, and sensory attributes. All plum ingredients reduced TBARS values and had minimal effects on tenderness, sensory characteristics, color and appearance. Small changes in purge, color values, TBARS and some sensory properties were found during storage. These results indicate that 2.5% FP or DP could be incorporated into precooked beef roasts to reduce lipid oxidation and potentially, warmed-over flavor (WOF).

Effectiveness of acidic calcium sulfate with propionic and lactic acid and lactates as postprocessing dipping solutions to control Listeria monocytogenes on frankfurters with or without potassium lactate and stored vacuum packaged at 4.5°C

The safety of ready-to-eat meat products such as frankfurters can be enhanced by treating with approved antimicrobial substances to control the growth of Listeria monocytogenes. We evaluated the effectiveness of acidic calcium sulfate with propionic and lactic acid, potassium lactate, or lactic acid postprocessing dipping solutions to control L. monocytogenes inoculated (ca. 10(8) CFU/ml) onto the surface of frankfurters with or without potassium lactate and stored in vacuum packages at 4.5 degrees C for up to 12 weeks. Two frankfurter formulations were manufactured without (control) or with potassium lactate (KL, 3.3% of a 60% [wt/wt] commercially available syrup). After cooking, chilling, and peeling, each batch was divided into inoculated (four strains of L. monocytogenes mixture) and noninoculated groups. Each group was treated with four different dips: (i) control (saline solution), (ii) acidic calcium sulfate with propionic and lactic acid (ACS, 1:2 water), (iii) KL, or (iv) lactic acid (LA, 3.4% of a 88% [wt/wt] commercially available syrup) for 30 s. Noninoculated frankfurters were periodically analyzed for pH, water activity, residual nitrite, and aerobic plate counts (APCs), and L. monocytogenes counts (modified Oxford medium) were determined on inoculated samples. Surface APC counts remained at or near the lower limit of detection (<2 log CFU per frank) on franks with or without KL and treated with ACS or LA throughout 12 weeks at 4.5 degrees C. L. monoctogenes counts remained at the minimum level of detection on all franks treated with the ACS dip, which indicated a residual bactericidal effect when L. monocytogenes populations were monitored over 12 weeks. L. monocytogenes numbers were also reduced, but not to the same degree in franks made without or with KL and treated with LA. These results revealed the effectiveness of ACS (bactericidal effect) or LA (bacteriostatic effect) as postprocessing dipping solutions to inhibit or control the growth of L. monocytogenes on vacuum-packaged frankfurters stored at 4.5 degrees C for up to 12 weeks.

Role of lactate dehydrogenase in metmyoglobin reduction and color stability of different bovine muscles

The role of lactate dehydrogenase (LDH) in metmyoglobin reducing activity (MRA) and color stability of different bovine muscles was studied in two consecutive experiments. In experiment 1, three different bovine muscles -M. longissimus lumborum (LL), M. semimembranosus (SM), and M. psoas major (PM) - were obtained (n=7, respectively), cut into steaks, PVC packaged, and then displayed for 7days at 1°C. The LL was the most red over display time and had more (P<0.05) LDH-B activity (catalyzing toward NADH generation), LDH1 isoform expression, NADH, and higher (P<0.05) MRA than the other two muscles studied. The PM had the least color stability and lowest MRA. In experiment 2, LL steaks (n=8) were cut in half, one side syringe-injected with oxamate, and the other injected with distilled water. Inclusion of oxamate decreased (P<0.05) LDH-B activity, NADH, and a* values after 10days display at 1°C. These results suggest that variation in color stability of physiologically different muscles is regulated by different replenishment rates of NADH via different LDH isozymes.

Survey of residual nitrite and nitrate in conventional and organic/natural/uncured/indirectly cured meats available at retail in the United States.

A survey of residual nitrite (NO(2)(-)) and nitrate (NO(3)(-)) in cured meats available at retail was conducted to verify concentrations in conventional (C) products and establish a baseline for organic/natural/uncured/indirectly cured (ONC) products. In this study, 470 cured meat products representing six major categories were taken from retail outlets in five major metropolitan cities across the United States. Random samples representing both C and ONC type products were analyzed for NO(2)(-) and NO(3)(-) content (ppm) using an ENO-20 high-performance liquid chromatography system equipped with a reverse phase column. Generally, there were no differences in NO(2)(-) concentrations between C and ONC meat categories, but a few ONC products surveyed in certain cities were lower in NO(3)(-) content. Pairwise comparisons between cities indicated that NO(2)(-) and NO(3)(-) contents of all C type products were not appreciably different, and the same was true for most ONC products. Numerical NO(2)(-) values were less variable than NO(3)(-) concentrations within each meat product category. NO(2)(-) concentrations were similar to those previously reported by Cassens ( Cassens , R. G. Residual nitrite in cured meat . Food Technol. 1997a , 51 , 53 - 55 ) in 1997. Residual NO(2)(-) and NO(3)(-) values in this study were numerically lower than those reported by NAS ( National Academy of Sciences . The Health Effects of Nitrate, Nitrite, and N-Nitroso Compounds ; National Academy Press : Washington, DC , 1981 ) in 1981. Data from this survey provide a benchmark of NO(2)(-) and NO(3)(-) concentrations for ONC products available at retail.

Qualitative effects of fresh and dried plum ingredients on vacuum-packaged, sliced hams.

Boneless ham muscles (Semimembranosus+Adductor) were injected (20% w/w) with a curing brine containing no plum ingredient (control), fresh plum juice concentrate (FP), dried plum juice concentrate (DP), or spray dried plum powder (PP) at 2.5% or 5%. Hams were cooked, vacuum-packaged, stored at<4°C and evaluated at 2-week intervals over 10 week. Evaluations were performed on sliced product to determine cook loss, vacuum-package purge, Allo-Kramer shear force, 2-thiobarbituric acid-reactive substances (TBARS), proximate analysis, objective color, sensory panel color and sensory attributes. FP, DP and 2.5% PP increased (P<0.05) cook loss by 2% to 7% depending on treatment and level, but the highest cook loss (17.7%) was observed in hams with 5% PP. Shear force values increased as the level of plum ingredient increased (P<0.05) from 2.5% to 5%, and the highest shear values were observed in hams containing 5% FP. There were no differences (P>0.05) in lipid oxidation among treatments as determined by TBARS and sensory evaluation. FP and PP ham color was similar to the control, but DP had a more intense atypical color of cured ham. Minimal changes in physical, chemical and sensory properties were observed during storage of all treatments.

Color stability and biochemical characteristics of bovine muscles when enhanced with L- or D-potassium lactate in high-oxygen modified atmospheres

Two different bovine muscles -M.longissimus lumborum (LD) and M. psoas major (PM) - were injection-enhanced (n=10, respectively) with solutions containing phosphate and potassium L- or D-lactate, cut into steaks, packaged with a high-oxygen (80% O(2)) modified atmosphere packaging, stored 9d at 2°C and then displayed for 5d at 1°C. Instrumental color, total reducing activity (TRA), lactate dehydrogenase (LDH) activity, and NADH were measured. Enhancement with L-lactate resulted in less color deterioration, and higher a(∗) and chroma values (P<0.05) than non-enhanced control of the bovine muscles. L-lactate enhancement significantly increased NADH concentration and TRA of LD and PM than the non-enhanced control through increased LDH-B flux at 14d. This study presents supportive evidence that the lactate-LDH system remains active for muscles with different metabolic activities and may be a possible mechanism of the lactate-color stabilization effect. Further, L-lactate enhancement can be utilized for improving muscles with lower color stability in high-oxygen modified atmosphere.