Hygiene status and cleaning effect evaluation of freezers in domestic refrigerators

Abstract

ObjectiveTo investigate the current status of microbial contamination in domestic freezers and evaluate the microbial improvement effects of professional refrigerator cleaning.MethodsSamples were collected aseptically from the food dividers， vegetable frames， and door seals of 15 household refrigerators before and after cleaning in Chengdu City. A total of 90 samples were obtained. The total number of bacteria， fungi， and coliforms in the samples was determined to reflect the sanitary conditions of the refrigerator. Coliform bacteria， Staphylococcus aureus， Salmonella， Listeria monocytogenes and Yersinia enterocolitica were isolated and cultured to determine the contamination status of these pathogenic bacteria. The effect of refrigerator cleaning was analyzed comprehensively according to microorganism detection and clearance rates before and after cleaning.ResultsBefore cleaning， the total number of bacteria in the refrigerator ranged from 2.4×103 to 1.4×105 CFU/cm2. After cleaning， the total number of bacteria ranged from 0 to 230 CFU/cm2. The bacterial clearance rates of the food dividers， vegetable frames， and door seals were 99.90%， 99.89%， and 99.81%， respectively. Before cleaning， the total number of fungi in the refrigerator ranged from 0 to 750 CFU/cm2. After cleaning， the total number of fungi in the refrigerator ranged from 0 to 58 CFU/cm2. The fungal clearance rates for the partition， vegetable frame， and door seal were 99.40%， 96.99%， and 99.41%， respectively. Before cleaning， the average detection rates of coliform bacteria， Staphylococcus aureus and Salmonella， were 64.44%， 13.33%， and 2.22%， respectively； Listeria monocytogenes and Yersinia enterocolitica were not detected. After washing， the average coliform bacteria detection rate was 13.33%； Staphylococcus aureus， Salmonella， Listeria monocytogenes， and Yersinia enterocolitica were not detected.ConclusionThis study revealed the presence of a high number of bacteria and fungi in the freezers of domestic refrigerators before cleaning， with S. aureus and Salmonella contamination. After professional cleaning， their sterility significantly improved， notably reducing potential food safety risks.

Keywords

• household refrigerator
• cold storage
• microbial contamination
• cleaning effect