J. C. Acton

Effects of packaging atmospheres on shelf-life quality of ground ostrich meat.

Fresh ground ostrich meat was packaged under high oxygen (O2), high nitrogen (N2), vacuum (VAC) and ambient air (AIR) atmospheres, stored at 4±1°C and displayed under 1700±100lux of fluorescent lighting for 9 days. The meat was evaluated for changes in typical shelf-life characteristics consisting of pH, color properties (CIE L(∗), a(∗), b(∗), and total color difference, ΔE), oxidative changes (thiobarbituric acid value and hexanal content) and bacterial counts (total viable cell, coliform, lactic acid bacteria, Enterobacteriaceae, Pseudomonas spp.) Initial meat pH was 6.16 and declined slightly during storage. TBA values and hexanal content were highest in O2 and lowest (P⩽0.05) in VAC and N2 atmospheres. Surface lightness (L(∗)) and redness (a(∗)) were highest in O2 packaging initially, decreasing (P⩽0.05) by day 9. ΔE of the ground ostrich increased during storage in only O(2) and AIR packaging. All packaging methods had generally similar effects on microbial outgrowth. Total aerobic bacteria attained >10(6) CFU/g meat between day 3 and day 6. Ground ostrich meat was below saleable quality in less than 6 days based on all of the meat attributes. For O2 packaging however, quality based on lipid oxidation and color properties indicated a shelf-life of less than 3 days. Oxidation is likely the limiting factor for shelf-life of ground ostrich meat.

Nisin release from films is affected by both protein type and film-forming method

Abstract Effects of protein type (wheat or corn) and film-forming method (casting or heat-pressing) on films were evaluated for the retention of biologically active nisin (Nisaplin) and release of activity into water at four different temperatures (5, 25, 35 and 45 °C). Nisin activity was measured using the agar diffusion method against Lactobacillus plantarum 1752. Cast corn zein (CCZ) and cast wheat gluten (CWG) films retained 12.1% (8.1×104 IU/g film) and 15.8% (1.1×105 IU/g film) of the original activity after film formation, respectively. Heat-pressed corn zein (HPCZ) and heat-pressed wheat gluten (HPWG) films retained 6.5% (4.3×104 IU/g film) and 7.4% (4. 9×104 IU/g film) of the original activity after film formation, respectively. The maximum nisin activity found migrating into water at any sampling time was 561 IU/ml (CCZ), 1058 IU/ml (CWG), 309 IU/ml (HPCZ), and 478 IU/ml (HPWG).

Effect of combining nisin and/or lysozyme with in-package pasteurization for control of Listeria monocytogenes in ready-to-eat turkey bologna during refrigerated storage

This study investigated the efficacy of in-package pasteurization combined with pre-surface application of nisin and/or lysozyme to reduce and prevent the subsequent recovery and growth of Listeria monocytogenes during refrigerated storage on the surface of low-fat turkey bologna. Sterile bologna samples were treated with solutions of nisin (2 mg/ml=5000 AU/ml), lysozyme (10 mg/ml=80 AU/ml) and a mixture of nisin and lysozyme (2 mg nisin+10mg lysozyme/ml) before in-package pasteurization at 65 degrees C for 32s. In-package pasteurization resulted in an immediate 3.5-4.2 log CFU/cm(2) reduction in L. monocytogenes population for all treatments. All pasteurized treatments also resulted in a significant reduction of L. monocytogenes by 12 weeks compared to un-pasteurized bologna. In-package pasteurization in combination with nisin or nisin-lysozyme treatments was effective in reducing the population below detectable levels by 2-3 weeks of storage. Results from this study could have a significant impact for the industry since a reduction in bacterial population was achieved by a relatively short pasteurization time and antimicrobials reduced populations further during refrigerated storage.

Utilization of response surface modeling to evaluate the effects of non-meat adjuncts and combinations of PSE and RFN pork on water holding capacity and cooked color in the production of boneless cured pork

Boneless cured pork was produced from combinations of pale, soft, and exudative (PSE) and red, firm, and non-exudative (RFN) semimembranosus muscle. Response Surface Methodology was utilized to determine the effects of soy protein concentrate (SPC), sodium caseinate (SC), and modified food starch (MFS) on the water holding capacity and cooked color in a chunked and formed product. Fifteen ingredient combinations were replicated three times for each PSE and RFN combination giving 75 treatments per replication. Utilization of SPC decreased (P<0.01) cooking loss and redness while increasing (P<0.01) yellowness. MFS decreased (P<0.01) expressible moisture, and both MFS and SC increased (P<0.05) cooked redness while decreasing (P<0.01) cooked lightness. Product formulations using these adjuncts demonstrate potential to improve the water-holding capacity and cooked color in PSE as well as RFN pork. This research also demonstrated that diluting RFN pork with no more than 25% PSE pork permits the formation of a high quality boneless deli ham roll.

Effect of combining nisin and/or lysozyme with in-package pasteurization on thermal inactivation of Listeria monocytogenes in ready-to-eat turkey bologna.

Achieving a targeted lethality with minimum exposure to heat and preservation of product quality during pasteurization is a challenge. The objective of this study was to evaluate the effect of nisin and/or lysozyme in combination with in-package pasteurization of a ready-to-eat low-fat turkey bologna on the inactivation of Listeria monocytogenes. Sterile bologna samples were initially treated with solutions of nisin (2 mg/ml = 5,000 AU/ml = 31.25 AU/cm2), lysozyme (10 mg/ml = 80 AU/ml = 0.5 AU/cm2), and a mixture of nisin and lysozyme (2 mg/ml nisin + 10 mg/ml lysozyme = 31.75 AU/cm2). Bologna surfaces were uniformly inoculated with a Listeria suspension resulting in a population of approximately 0.5 log CFU/cm2. Samples were vacuum packaged and subjected to heat treatment (60, 62.5, or 65 degrees C). Two nonlinear models (Weibull and log logistic) were used to analyze the data. From the model parameters, the time needed to achieve a 4-log reduction was calculated. The nisin-lysozyme combination and nisin treatments were effective in reducing the time required for 4-log reductions at 62.5 and 65 degrees C but not at 60 degrees C. At 62.5 degrees C, nisin-lysozyme-treated samples required 23% less time than did the control sample to achieve a 4-log reduction and 31% less time at 65 degrees C. Lysozyme alone did not enhance antilisterial activity with heat. Results from this study can be useful to the industry for developing an efficient intervention strategy against contamination of ready-to-eat meat products by L. monocytogenes.

Antibacterial effects of natural tenderizing enzymes on different strains of Escherichia coli O157:H7 and Listeria monocytogenes on beef.

This study determined the efficacy of actinidin and papain on reducing Listeria monocytogenes and three mixed strains of Escherichia coli O157:H7 populations on beef. The average reduction of E. coli O157:H7 was greater than that of L. monocytogenes and higher concentrations of either protease yielded greater reduction in bacterial populations. For instance, actinidin at 700 mg/ml significantly (p≤0.05) reduced the population of L. monocytogenes by 1.49 log cfu/ml meat rinse after 3h at 25 & 35 °C, and by 1.45 log cfu/ml rinse after 24h at 5 °C, while the same actinidin concentration significantly reduced the populations of three mixed strains of E. coli O157:H7 by 1.81 log cfu/ml rinse after 3h at 25 & 35 °C, and 1.94 log cfu/ml rinse after 24h at 5 °C. These findings suggest that, in addition to improving the sensory attributes of beef, proteolytic enzymes can enhance meat safety when stored at suitable temperatures.

Thermal Effects on Net Protein Ratio of Red Kidney Beans (Phaseolusvulgaris L)

Net protein ratio (NPR), predicted-protein efficiency ratio (P-PER), relative NPR (RNPR), and corrected RNPR (CRNPR) of thermally processed red kidney beans were estimated in rats and compared to in vitro protein digestibility-corrected amino acid score (AAS IVDP ), and computed-protein efficiency ratio (C-PER). Thermal processing had a significant effect on protein intake, NPR, P-PER and CRNPR values of beans. Changes in protein intake suggest that heat processing had an effect on the palatability of the beans. Home-cooked beans and commercially canned beans had higher NPR values than beans autoclaved at 128°C for 20 min, while beans autoclaved at 121°C for 10-90 min had intermediate values. High correlation coefficients between P-PER and C-PER, CRNPR and C-PER, and CRNPR and AAS IVDP (r = 0.990, 0.992 and 0.960, respectively, P < 0.001)were observed.

Microbial Persistence on Inoculated Beef Plates Sprayed with Hypochlorite Solutions

Exterior surfaces of beef plates were inoculated with aerobic mesophilic, psychrotrophic, coliform, fecal coliform and Staphylococcus aureus bacteria before spraying with city water (7.03 kg/cm2) or with 100, 150 or 200 ppm hypochlorite solutions applied at 3.75, 5.25 or 7.03 kg/cm2) for 12 sec. Surface strips excised from the inoculated carcass regions were analyzed for bacterial persistence at 2 hand 2,4,8,16 and 20 days after spray treatment. A one log. or greater, reduction incoliforms, fecal coliforms and S. aureus counts occurred within 4 days for each spray treatment. Initial aerobic mesophilic and psychrotrophic counts were reduced by < 1 log within 2 h but increased to original inoculum levels within 8 days for each treatment. Mesophilic and psychrotrophic counts increased to > 3.5 logs higher than inoculated levels after 16 days at 4-6 C. Spray pressure (P < .01) was more effective in reducing mesophilic, psychrotrophic and S. aureus counts than was hypochlorite concentration (P < .05) while both variables were about equally effective against coliforms (P < .01) and fecal coliforms (P < .05). Surprisingly, reductions of psychrotrophic, coliform and S. aureus counts on the beef carcass surface sprayed with hypochlorite solutions were not significantly (P < .05) different from those observed on carcasses sprayed with city water. However, a significantly (P < .05) greater reduction in aerobic mesophile and fecal coliform counts at 2 days after treatment was obtained when using the intermediate spray pressure of 5.25 kg/cm2 containing 200 ppm hypochlorite, rather than city water. No undesirable change in beef grade, muscle shear or color property was observed for carcasses treated with the hypochlorite solutions.

Nitrosoheme Pigment Formation and Light Effects on Color Properties of Semidry, Nonfermented and Fermented Sausages

Development of the nitrosoheme pigment responsible for visual color properties was studied in the preparation of cured, semidry nonfermented and fermented sausages. Color stability of vacuum packaged sausages differing in pH was also evaluated during 6 weeks of light exposure, and after 6 weeks in dark storage. Total pigment conversion to nitrosoheme increased (P<0.05) during 9.75 h of fermentation at 38°C. The maximum pigment conversion attained upon heat processing to 60°C appeared dependent on prior nitrosoheme formation during fermentation. Judd-Hunter tristimulus coordinates of semidry sausages showed higher (P<0.05) initial +a (redness) values when the pH was 4.85 or 4.65 as compared to pH 5.30 or 6.00. During 6 weeks of light exposure, sausage pH, and time in display were significant factors for each color property. By the fourth and sixth weeks of light exposure, nonfermented sausages (pH 6.0) had maintained redness characteristics better than all fermented sausages (pH 5.30, 4.85, and 4.65) as shown by higher +a and lower hue angle (θ) values. After 6 weeks of light exposure or dark storage, there were no differences (P>0.05) in any color property or nitrosoheme pigment content for nonfermented sausages. However, light exposure, as compared to dark storage, altered (P<0.05) all color properties and reduced (P<0.05) the nitrosoheme pigment content for fermented sausages.