Effect of different alkali treatments on the chemical composition, physical properties, and microstructure of pidan white.

Changes in chemical composition, physical property and microstructure of pidan white treated with 4.5 % NaOH or 5.5 % KOH were monitored during pickling up to 4 weeks, and followed by aging for another 2 weeks. As the pickling and ageing times increased, moisture content of pidan white decreased and salt content increased for both (4.5 % NaOH and 5.5 % KOH) treatments (P < 0.05). Free alkalinity and pH of pidan white treated with 4.5 % NaOH increased as pickling proceeded, but decreased during ageing for both pickling treatments (P < 0.05). At week 4 of pickling, pidan white treated with 5.5 % KOH had higher hardness, cohesiveness, gumminess and chewiness than those treated with 4.5 % NaOH. After ageing, higher springiness, elastic modulus (G') and viscous modulus (G") were generally found in pidan white treated with 5.5 % KOH (P < 0.05). As the pickling time increased, lower L*, b* values and higher a* value were observed in pidan white from both treatments (P < 0.05). As visualized by scanning electron microscope, the aggregation of egg proteins took place in pidan white gels, irrespective of pickling treatments used. Nevertheless, closer and more orderly protein aggregates with denser network were founded in pidan white treated with 5.5 % KOH.

Quality preservation of reduced sodium pork patties: effects of antioxidants on colour and lipid stability.

BACKGROUND: The purpose of this study was to explore the effect of lipid oxidation and colour change of precooked pork patties with reduced sodium and added antioxidants. This study can fill the gap of antioxidant application between meat products with regular and low salt content. RESULTS: For precooked pork patties, addition of sodium tripolyphosphate and carnosine increased pH values and cooking yields. Patties with ascorbic acid had significantly higher a* values compared to the other samples. There was no significant difference of b* values among treatments. Precooked pork patties with sodium tripolyphosphate or carnosine had significantly higher L* values compared to other patties. The addition of antioxidants reduced lipid oxidation in precooked pork patties during refrigerated storage, except for the addition of 0.5% carnosine. CONCLUSION: Tripolyphosphate and ascorbic acid were successfully proven to be effective in retarding lipid oxidation and preserve the colour stability in reduced salt pork patties. This study provides a preliminary foundation of keeping meat products from lipid oxidation and maintaining in better stability.

Effects of Electrical Stimulation on Lipid Oxidation and Warmed-over Flavor of Precooked Roast Beef.

Many manufacturing processes damage the structure of meat products and this often contributes to lipid oxidation which could influence warmed-over flavor (WOF) in precooked beef that is reheated beef. Electrical stimulation causes contraction of muscles and improves tissue tenderization. The purpose of this study was to evaluate the rate of lipid oxidation or warmed-over flavor that could be affected by electrical stimulation of precooked roast beef after refrigerated storage and reheating. The results show that there was no significant difference between chemical compositions and cooking yields when comparing non-electrically stimulated and electrically stimulated roast beef. Moreover, electrical stimulation had no significant effect on oxidative stability and off-flavor problems of precooked roast beef as evaluated by thiobarbituric acid reactive substances (TBARS) and sensory test (warmed-over aroma and warmed-over flavor). However, there was an increased undesirable WOF and a decrease in tenderness for both ES and Non-ES treatments over refrigerated storage time. Electrical stimulation did cause reactions of amino acids or other compounds to decrease the desirable beef flavor in re-cooked meat.

Effect of phosphate, ascorbic acid and α-tocopherol injected at one-location with tumbling on quality of roast beef.

The purpose of this study was to evaluate if continuous non-vacuum or vacuum tumbling improves the quality of roast beef utilizing the one location injection. Basically, fresh roast beef treated by one location injection with tumbling had significantly different quality compared to non-tumbled ones. However, the cooked roast beef did not significantly exhibit better quality due to tumbling. There was insignificant difference of TBARS value for whole meat among treatments at day 0. The control had significantly higher TBARS value compared to roast beef with non-vacuum and vacuum tumbled samples at day 2. At 4, 7 and 14 days of refrigerated storage, the control maintained the significantly highest values when compared to the other treatments that had similar TBARS values. The addition of three antioxidants was the major contributor to lipid stability of the cooked roast beef.

Lipid oxidation and color change of salted pork patties.

The purposes of this study were to explore the interaction of lipid oxidation and pigment oxidation in salted pork patties and to study the mutual relationship between lipid and pigment oxidation caused by replacing sodium chloride with potassium chloride at low salt levels. For fresh pork patties, a(∗) and b(∗) values decreased with the replacement of sodium chloride by potassium chloride. However, there were no significant differences of L(∗) values, pH values, total pigments and heme irons by replacement of NaCl with KCl; however, the replacement reduced 2-thiobarbituric acid reactive substances (TBARS). The addition of sodium tripolyphosphate, ascorbic acid and carnosine did not change a(∗) and b(∗) values of raw pork patties. However, raw pork patties with 0.25% sodium tripolyphosphate had significantly higher L(∗) value compared to other samples. The pH of raw pork patties with 0.5% carnosine was higher than those of other treatments. The pH of raw pork patties with 0.25% sodium tripolyphosphate was significantly higher than that of the control treatment with no antioxidant. Samples with 550ppm ascorbic acid had significantly higher total pigment and heme iron than patties with 0.25% sodium tripolyphosphate. Although control treatment with no antioxidant had slightly higher TBARS values, these differences were not large enough to be significant.

Sensitivity of three pathogenic bacteria to Turkish cemen paste and its ingredients.

Pastirma is a dry cured meat product which is pasted with cemen. This paste is prepared from ground fenugreek, garlic and red hot pepper (RHPP). In this study, the cemen mix/paste and all its ingredients were tested for their inhibitory effects on Escherichia coli, Staphylococcus aureus and Yersinia enterocolitica. All samples had a varying inhibitory effect against all the bacteria tested during 4 days of storage. Complete cemen paste showed the strongest inhibitory effect on the three pathogens compared to ingredients alone. Fenugreek and RHPP had a bacteriostatic effect while the cemen paste and garlic had a bactericidal effect. S. aureus was the most sensitive bacterium while Y. enterocolitica was the most resistant. The results of this study confirmed the protective effect of cemen paste and garlic in food preservation especially against E. coli, S. aureus and Y. enterocolitica proving safety for public health. Hence it might be concluded that cemen paste is the first hurdle to prevent bacterial contamination, and a low pH (∼4.83) value would also add an additional barrier to secure safety of the product. Finally, it can be suggested that similar studies should be conducted on actual meat systems to confirm these findings.

Effect of phosphate with tumbling on lipid oxidation of precooked roast beef.

This study was a 4×2×4 factorial experiment, sodium tripolyphosphate (0, 0.25, 0.4 and 0.5%), tumbling (nontumbled and tumbled), and storage time (day 0, 2, 4 and 7). Cooking yield was dependent on the level of phosphate and tumbling. For thiobarbituric acid reactive substances (TBARS) values, only sodium tripolyphosphate level and storage time had a significant two-way interaction. The TBARS value of tumbled roast beef with phosphates was the same as that of nontumbled roast beef. For the interaction of phosphate level and storage time, roast beef without phosphate had the significantly highest TBARS values compared with other phosphate levels at day 4 of storage. At day 7, the addition of 0.5% phosphate maintained the oxidative stability of precooked roast beef. The use of 0.5% sodium tripolyphosphate, an iron chelator, should be an effective strategy to reduce the formation of TBARS in precooked roast beef.

Inactivation and Attachment of Listeria monocytogenes on Beef Muscle Treated with Lactic Acid and Selected Bacteriocins.

Cubical pieces (1 cm3) of aseptically obtained beef muscle were treated with lactic acid (2%), nisin (4 × 104 IU/ml) and pediocin PO2 (a bacteriocin produced by Pediococcus acidilactici PO2; 3.2 × 103 arbitrary units/ml). Treated meat was immersed for 1 min in a cell suspension of a mixture of two strains of Listeria monocytogenes and then stored for 48 h at 4°C. Meat cubes were analyzed immediately after immersion in the cell suspension, then after 1, 24, and 48 h of storage. Count of L. monocytogenes per cube and percentage of attached cells were determined. Data indicated that the antimicrobial agents significantly (p = 0.05) decreased the count of L. monocytogenes during the 48-h storage by 1.7, 1.1, and 0.6 log10 CFU/6 cm2 of meat surface for lactic acid, nisin, and pediocin PO2 treatments, respectively. Lactic acid on the meat surface had an immediate and also a delayed listericidal action, but bacteriocins only inhibited L. monocytogenes immediately, and had little or no delayed antilisterial effect. The percentage of Listeria cell attached to the beef muscle significantly (p = 0.05) increased in the presence of lactic acid, but the value did not change significantly or slightly decreased in the presence of nisin and pediocin PO2, respectively.