Antimicrobial activity of chitosan‐based films against Salmonella typhimurium and Staphylococcus aureus

The antibacterial effect of polyamide 6/66‐chitosan blend and chitosan‐coated plastic films was compared to chitosan films and chitosan solution, against Salmonella typhimurium and Staphylococcus aureus. The chitosan films did not show inhibition halos; however, contact inhibition was observed. During the tests, the films absorbed moisture, increasing of the diameter discs in relation to the concentration of the chitosan for both microorganisms at least 31%. Chitosan plastic film coating (bilayer system) showed only contact inhibition, without increase in contact area. The films from polyamide 6/66‐chitosan blend had no antibacterial activity. The highest inhibitory effect resulted from a chitosan solution at 1000 and 2000 ppm for S. typhimurium and S. aureus, respectively. The results of this study showed that the antimicrobial activity was lessened when the chitosan was combined with the plastic matrix because of the absence of contact inhibition, and the best activity was obtained with films prepared by casting of chitosan solution.     

A novel emulsion coating and its effects on internal quality and shelf life of eggs during room temperature storage

Effects of mineral oil (MO), chitosan solution (CH) and their emulsions (MO:CH = 75:25, 50:50, and 25:75 ratios) as coating materials in preserving internal quality of eggs were evaluated during a 5‐weeks storage at 25 °C. Consumers (n = 109) evaluated surface properties and purchase intent of freshly coated eggs. As storage time increased, Haugh unit and yolk index values decreased whereas weight loss increased. Noncoated eggs rapidly changed from AA to B and C grades after 1 and 3 weeks, respectively. However, all emulsion‐coated eggs maintained their A‐grade quality for 4 weeks. Compared with noncoated eggs, all emulsion coatings reduced weight loss of eggs by at least seven times (0.88–1.03% vs. 7.14%). Only MO:CH = 25:75 emulsion‐coated eggs were not sensorially glossier than noncoated eggs. All emulsion‐coated eggs had >80% positive purchase intent and were negative for Salmonella. This study demonstrated that MO:CH emulsion coatings preserved internal quality and prolonged shelf life of eggs.     

甘草多糖对肉仔鸡肠道微生物调控的研究

研究饲料中添加甘草多糖对肉鸡肠道微生物区系的调节作用。试验分5个组,其中3个组饲喂分别添加0.5、1.0和1.5g/kg甘草多糖的饲料,1个组饲喂添加0.09g/kg金霉素的饲料,1个组饲喂基础日粮作为对照。结果表明:1.0g/kg甘草多糖组肠道大肠杆菌数和沙门氏菌数均比对照组低(P<0.05),与金霉素组相比差异不显著。肠道优势菌群乳酸杆菌数和双歧杆菌数在15日龄时高于对照组(P>0.05)和金霉素组(P<0.05);30日龄时高于对照组(P<0.05),但低于金霉素组(P<0.05)。甘草多糖适宜的添加水平为1.0g/kg。     

Role of peroxyacetic acid, octanoic acid, malic acid, and potassium lactate on the microbiological and instrumental color characteristics of ground beef

Abstract: This study evaluated the effects of peroxyacetic acid (PAA), malic acid (MA), octanoic acid (OA), and potassium lactate (KL) followed by mixing with trisodium phosphate (TSP) and an ultra‐chilled CO₂ snow shower on microbial counts of Escherichia coli (EC), coliform (CF), aerobic plate count (APC), and Salmonella Typhimurium (ST) on inoculated beef trimmings and the instrumental color attributes of the resultant ground beef. Beef trimmings inoculated with EC and ST were treated with either 0.02% PAA; 2% MA; 0.04% OA; or 2% KL, followed by mixing with 10% TSP and rapid chilling with CO₂ snow shower. Treated trimmings were then ground, packaged, displayed under simulated retail conditions, and sampled on days 1, 2, 3, 5, and 7 for microbial counts and instrumental color characteristics. PAA, MA, OA, and KL reduced (P < 0.05) the microbial counts of EC, CF, APC, and ST during display. Among treatments, OA was most effective on EC, CF, ST, and APC during retail display. Chilling beef trimmings with CO₂ improved instrumental color characteristics of the produced ground beef but made little difference in reducing microbial counts during display. During retail display, ground beef produced from beef trimmings treated with antimicrobials tended to maintain redness, myoglobin redox form stability (630 nm/580 nm), and overall instrumental color characteristics. Practical Application: This research provides a practical and cost‐effective decontamination technology for beef processors that can be immediately implemented in the ground beef production chain. Using antimicrobial intervention coupled with rapid chilling could benefit the meat industry by preserving the quality attributes of ground beef during retail display under aerobic packaging environment.     

Survival of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella spp. on Catfish Fillets Exposed to Microwave Heating in a Continuous Mode

Microwave (MW) heating using continuous power output with feedback control and a modified ingredient formulation may provide better and consistent cooking of foods. Currently, household units with build-in inverter power supply units are available. These new generation MW ovens provide continuous, adjustable output and cooking, in contrast to the traditional rectifier-based ovens that rely on the on-off mechanism for control. This study attempted to apply a feedback power control (termed as modified or "smart" MW oven) and phosphate treatment to further improve heating uniformity and enhance food quality and safety. Listeria monocytogenes (Lm, 4-strain cocktail), Escherichia coli O157:H7 (Ec, 5-strain cocktail), and Salmonella spp. (Sal, 6-strain cocktail), surface inoculated onto catfish fillets (75 × 100 × 15 mm; weight 110 g), were heated using the modified MW oven to study the inactivation of the pathogens. The sensitivity of these 3 bacteria to MW heating was in the order of Ec (most), Lm, and Sal (least). Greater than 4 to 5 log CFU reductions of Ec, Lm, or Sal counts on catfish fillet surfaces were inactivated within 2 min of 1250 W MW heating, where the fillet surface temperature increased from 10 to 20 °C to 80 to 90 °C. MW heating caused degradation of catfish fillet texture, which was noticeable as early as 10 to 15 s after the heating started, as evidenced by bumping sounds. Bumping can be significantly reduced by soaking fillets in phosphate solution. However, the results may need verification if applied in different MW ovens and/or with foods positioned away the geometric oven center. This study successfully demonstrated the feasibility of applying MW energy to eliminate foodborne pathogens on fish fillets. Practical Application: The results demonstrated in this report with the "smart" microwave oven design may enhance microwaveable food safety and quality, and therefore promote the microwaveable food business.     

Advances in enteropathogen control throughout the meat chicken production chain

Enteropathogens, namely Salmonella and Campylobacter, are a concern in global public health and have been attributed in numerous risk assessments to a poultry source. During the last decade, a large body of research addressing this problem has been published. The literature reviewed contains review articles on certain aspects of poultry production chain; however, in the past decade there has not been a review on the entire chain—farm to fork—of poultry production. For this review, a pool of 514 articles were selected for relevance via a systematic screening process (from >7500 original search articles). These studies identified a diversity of management and intervention strategies for the elimination or reduction of enteropathogens in poultry production. Many studies were laboratory or limited field trials with implementation in true commercial operations being problematic. Entities considering using commercial antienteropathogen products and interventions are advised to perform an internal validation and fit-for-purpose trial as Salmonella and Campylobacter serovars and biovars may have regional diversity. Future research should focus on nonchemical application within the processing plant and how a combination of synergisticinterventions through the production chain may contribute to reducing the overall carcass burden of enteropathogens, coupled with increased consumer education on safe handling and cooking of poultry.