Effect of Thaw Conditions on Ground Beef 1

Microbiological analysis of frozen profiteroles and mini chocolate eclairs implicated in a national salmonellosis outbreak

Between November 2018 and May 2019, Canada experienced a nationwide salmonellosis outbreak linked to the presence of Salmonella enterica ser. Enteritidis in frozen profiteroles. Analysis of the implicated food products revealed low levels of Salmonella ranging from 0.2 to 0.7 MPN/100g. Water activity and pH of the food samples ranged from 0.9479 to 0.9867 and 4.6-6.8 respectively indicating conditions conducive to bacterial growth. Higher levels of the hygiene indicators Enterobacteriaceae and coliforms were associated with Salmonella positive samples compared to Salmonella negative samples. Investigation of the relationship between storage conditions, temperature, and pathogen levels during thawing revealed that the profiteroles reached temperatures permissive to pathogen growth (≥5 °C) much sooner than pathogen growth was observed and that the composition of the food matrix can influence bacterial levels upon thawing. Collectively these data can be used to inform guidance to minimize the risk of infection from the consumption of contaminated cream-filled frozen desserts.

Effect of Repeated Freeze-Thaw Cycles on Beef Quality and Safety

The objectives of this study were to know the effect of repeated freeze-thaw cycles of beef on the sensory, physicochemical quality and microbiological assessment. The effects of three successive freeze-thaw cycles on beef forelimb were investigated comparing with unfrozen fresh beef for 75 d by keeping at -20±1℃. The freeze-thaw cycles were subjected to three thawing methods and carried out to know the best one. As the number of freeze-thaw cycles increased color and odor declined significantly before cook within the cycles and tenderness, overall acceptability also declined among the cycles after cook by thawing methods. The thawing loss increased and dripping loss decreased significantly (p<0.05). Water holding capacity (WHC) increased (p<0.05) until two cycles and then decreased. Cooking loss increased in cycle 1 and 3, but decreased in cycle 2. pH decreased significantly (p<0.05) among the cycles. Moreover, drip loss, cooking loss and WHC were affected (p<0.05) by thawing methods within the cycles. 2-Thiobarbituric acid (TBARS) value increased (p<0.05) gradually within the cycles and among the cycles by thawing methods. Total viable bacteria, total coliform and total yeast-mould count decreased significantly (p<0.05) within and among the cycles in comparison to the initial count in repeated freeze-thaw cycles. As a result, repeated freeze-thaw cycles affected the sensory, physicochemical and microbiological qua- lity of beef, causing the deterioration of beef quality, but improved the microbiological quality. Although repeated freeze-thaw cycles did not affect much on beef quality and safety but it may be concluded that repeated freeze and thaw should be minimized in terms of beef color for commercial value and WHC and tenderness/juiciness for eating quality.

Thermal destruction of Escherichia coli O157:H7 in beef and chicken: determination of D- and z-values

Thermal inactivation of a four-strain mixture of E. coli O157:H7 was determined in 90% lean ground beef, and lean ground chicken. Inoculated meat was packaged in bags which were completely immersed in a circulating water bath and held at 55, 57.5, 60, 62.5, and 65 degrees C for predetermined lengths of time. D-values, determined by linear regression, in beef were 21.13, 4.95, 3.17, 0.93 and 0.39 min, respectively (z = 6.0 degrees C). Using a survival model for non-linear survival curves, D-values in beef ranged from 20.45 min (D1; and there was no D2) at 55 degrees C to 0.16 min (D1) and 1.45 min (D2) at 65 degrees C. When E. coli O157:H7 four-strain cocktail was heated in chicken, D-values calculated by both approaches were consistently less at all temperatures. The heat resistance of E. coli O157:H7 was not altered after refrigerated or frozen storage of inoculated beef for 48 h. The results of this study will be beneficial to the food industry in designing HACCP plans to effectively eliminate E. coli O157:H7 in the meat products used in this study.