Evaluation and Improvement of Microbiological Quality of Convenient Prepared and Minimally Processed Foods

• Main Authors: Che-Lun Hsu, 許哲綸
• Other Authors: Chihwei P. Chiu
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/20298912740576173184

碩士 === 輔仁大學 === 食品營養學系 === 88 === Ninety-seven commercial ready-to-use prepared foods from retail markets and factories were collected for microbiological analyses. Twelve of 47 refrigerated samples (25.5%) showed high aerobic plate count (APC), >105 CFU/g; whereas, 9 of 50 frozen samples (18%) had APC exceeding 105 CFU/g. Coliforms were detected from 14 samples, exceeding 10 MPN/g, and Escherichia coli was also found in 2 samples. Staphylococcus aureus was not detected. One hundred and forty five minimally processed foods were collected for microbiological analyses. Eighty-nine samples (61.4%) had APC exceeding 105 CFU/g. Coliforms were detected from 93 samples (64.1%), exceeding 10 MPN/g, and E. coli was also found in 2 samples, and S. aureus in 3 samples. The changes of microbial count and pH value were determined in spaghetti sauce, new spaghetti sauce and corn chowder during storage at —18, 4, 18, 25, 30, 40 and 50℃.All samples were not contaminated with coliforms, E. coli and S. aureus. The APC and the pH values of all samples maintained stable during storage at —18 and 4℃. The APC in spaghetti sauce and new spaghetti sauce increased after 24h storage at 25, 30 and 40℃, and reached 105 CFU/g after 48h. The APC of corn chowder was 102 CFU/g at 18℃after 24h storage, while it became greater than 105 CFU/g at other storage temperatures. The pH values did not change obviously at 18℃, whereas, it dropped to below 5.0 at 40 and 50℃ after 24h storage. The pH values of shredded lettuce dropped significantly (p<0.05) after immersion in various concentrations of acetic, lactic and citric acid for 30min. The inhibition effect of 1% acetic acid on APC and coliforms were significantly (p<0.05). As the level of acetic acid reached 2%, APC decreased to below 102 CFU/g, while coliforms were not detected when 0.1% lactic acid was in use. The APC was not detected when 3.0% citric acid was used, whereas coliforms count dropped to none when 0.3% citric acid was employed. With the treatment of hydrogen peroxide, the APC decreased by 2 log values. However, trace of hydrogen peroxide was also found in lettuces. E. coli and S. aureus were totally inhibited. Microbial evaluations of personnel, utensil, equipment, air and water were conducted in one minimally processed foods manufacturer. The APC of worker’s hands decreased from initial counts of 103-106 CFU/hand to 102-105 CFU/hand after washing with soap and water. Coliforms decreased 10-102 MPN/hand. None of E. coli and S. aureus was detected from worker’s hands. After cleaning, APC of equipment in the area of ready-to-use prepared foods, decreased 10102 CFU/cm2 and none of coliforms was detected. In food processing area, APC of equipment decreased 10-103 CFU/cm2, while coliforms were not found. The microbial count of air in the plant was below 30 CFU/plate/5min, which coliforms to the GMP regulation. The APC of water in the plant were below 102 CFU/mL. No coliforms, E. coli and S. aureus was found.