Under conditions of stress, cells of Campylobacter assume a coccoid shape that may be an evolutionary strategy evolved by the organism to enable survival between hosts. However, the physiology of Campylobacter as it devolves from spiral to coccoid-shaped morphology is poorly understood. In this study, conditions influencing the survival of Campylobacter jejuni ATCC 35921 in broth were determined. Cells in late log phase were resuspended in broth at 4 or 60 degrees C. The culturability of these cold- or heat-stressed cell suspensions was determined by spread plate counts and the activity of cells by the direct viable count technique and 5-cyano-2,3-ditolyltetrazolium chloride staining. C. jejuni changed form completely from culturable to viable but nonculturable cells (VBNC) within 25 days at 4 degrees C, and 15 min at 60 degrees C. Light microscopy of C. jejuni VBNC cells showed that the spiral-shaped cells became coccoid, and transmission electron microscopy of C. jejuni VBNC cells showed that the outer membrane was lost in aging cell suspensions. Furthermore, a limited proteomic study was carried out to compare C. jejuni proteins that exhibited increased or decreased synthesis on exposure to 60 degrees C.

ObjectiveThe objective of this research was to evaluate the physico-chemical, microbiological and sensorial qualities of restructured steaks processed from beef trimmings (grade I and II) and frozen beef (fresh beef as control and frozen beef).MethodsBeef trimmings from commercial butcher were collected, designated into 4 treatments differing in beef trimmings grade and freezing, processed into restructured steaks with 1% microbial transglutaminase and then analyzed for product quality.ResultsThe results showed that all meat from different groups could be tightly bound together via cross-linking of myosin heavy chain and actin as observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Microbial counts of psychrotrophic and mesophilic bacteria were not affected by treatments (p>0.05), and no detectable of thermophilic bacteria were found. Regarding effect of beef trimmings grade, steaks made from beef trimmings grade II (16.03% fat) showed some superior sensorial qualities including higher tenderness score (p<0.05) and tendency for higher scores of juiciness and overall acceptability (p<0.07) than those made from beef trimmings grade I (2.15% fat). Moreover, a hardness value from texture profile analysis was lower in steaks processed from beef trimmings grade II than those made from grade I (p< 0.05). Although some inferior qualities in terms of cooking loss and discoloration after cooking were higher in steaks made from beef trimmings grade II than those made from beef trimmings grade I (p<0.05), these differences did not affect the sensory evaluation. Frozen beef improved the soft texture and resulted in effective meat binding as considered by higher cohesiveness and springiness of the raw restructured product as compared to fresh beef (p<0.05).ConclusionThe results indicated the most suitable raw beef for producing restructured steaks without detrimental effect on product quality was beef trimmings grade II containing up to 17% fat which positively affected the sensory quality and that frozen beef trimmings increased tenderness and meat binding of restructured beef steaks.

The objective of this study was to investigate the in vitro activities of sodium diacetate (SD), sodium citrate (SC), or sodium lactate (SL) in combination with lauric arginate (LAE) against Listeria monocytogenes and Salmonella Rissen. Bacteria isolated from a pig carcass were used to determine the minimum inhibitory and bactericidal concentrations (MIC and MBC), fractional bactericidal concentration index (FBCI), time-kill method, as well as to perform scanning and transmission electron microscopy characterizations. For L. monocytogenes, the MBC of SD, SC, LAE and SL were 62.5, 62.5, 0.032 mg/ml, and 8.4% (v/v), respectively. As for S. Rissen, the MBC of SD and LAE were 62.5 and 0.032 mg/ml, respectively. The effects of SD, SC, and SL in combination with LAE were synergistic against both bacteria, exhibiting FBCIs of 0.19, 0.50, and 0.50, respectively, for L. monocytogenes and 0.19, 0.50 and 0.50, respectively, for S. Rissen. In time-kill studies, all salts of organic acids plus LAE combinations added at their MBC produced a bactericidal effect that was dependent on the type of bacteria and antimicrobial. This resulted in a loss and change of the cytoplasm and membrane in cells of both bacteria. Furthermore, SC and SL alone were not active in killing S. Rissen. The present investigation revealed that salts of organic acid in combination with LAE are potentially antilisterial and anti-salmonella agents, which can be applied to meat products.

ObjectiveThe influence of konjac gel level on fermentation process and product qualities were assessed to evaluate the feasibility of using it as fat analog in Northeastern Thai fermented sausage (Sai Krok E-san).MethodsFive treatments of fermented sausages were formulated by replacing pork backfat with 0%, 7.5%, 22.5%, and 30% konjac gel. The changes in lactic acid bacteria (LAB) and important physicochemical properties of samples were assessed during 3 days of fermentation. After the end of fermentation at day 3, water activity (aw), instrumental texture, color, microbial counts, and sensory evaluation were compared. The best product formulation using konjac for replacing pork back fat were selected and used to compare proximate composition and energy value with control sample (30% pork backfat).ResultsAn increase in konjac gel resulted in higher values of LAB, total acidity, and proteolysis index with lower pH and lipid oxidation during 3 days of product fermentation (p< 0.05). It was noted that larger weight loss and product shrinkage during fermentation was observed with higher levels of konjac gel (p<0.05). The resulting sausage at day 3 with 15% to 30% konjac gel exhibited higher hardness, cohesiveness, gumminess, springiness, and chewiness than control (p<0.05). The external color of samples with 22.5% to 30% konjac gel were redder than others (p<0.05). Mold, Salmonella spp., Staphylococcus aureus, and Escherichia coli in all finished products were lower than detectable levels. Product with 15% konjac gel had the highest scores of sourness linking and overall acceptability (p<0.05).ConclusionThe product with 15% of konjac gel was the optimum formulation for replacing pork backfat. It had higher sensorial scores of sourness and overall acceptability than control with less negative impact on external appearance (product shrinkage) and weight loss. Moreover, it provided 46% fat reduction and 32% energy reduction than control.

Lauric acid and monolaurin in combination with lactic acid were evaluated for their effectiveness in reducing total plate count (TPC) and Staphylococcus aureus of fresh pork loin. Fresh pork loins were dipped in control (non treated), sterile distilled water, 3.2 mg/ml lauric acid, 0.4% (v/v) lactic acid, 0.2 mg/ml lauric acid + 0.1% (v/v) lactic acid, 0.1 mg/ml monolaurin, 0.05 mg/ml monolaurin + 0.1% (v/v) lactic acid solution. Total plate count, population of S. aureus and physical and sensory qualities were determined. TPC and S. aureus counts found in pork loin treated with lauric acid and monolaurin alone and in combination with lactic acid were not significantly different (P > 0.05). The colour, odour and overall acceptability of the pork loins were adversely affected by the treatment with lactic acid alone, but when combinations of the agents were used the sensory quality was acceptable. Furthermore, during storage, both lipids in combination with lactic acid controlled growth of S. aureus for 8 and 4 days of storage at 4 and 15°C respectively, and TPC for 8 and 2 days of storage at 4 and 15°C, respectively. The low pH of the antimicrobials caused the highest weight loss of range 4.41-5.38% drip loss, 22.56-23.35% cooking loss, and discolouration. In contrast, L * , PV, TBARS of pork in all treatments increased but shear force and a * decreased as storage was longer in all solution types (P < 0.05). However, for sensory acceptability, there was no loss of colour or adverse odour and the overall acceptability scores remained satisfactory.