Thermal fogging with disinfectants and antifreezes enables effective industrial disinfection in subzero cold-chain environment.

AIM: During several local COVID-19 outbreaks in China in 2020, SARS-CoV-2 or its RNA was isolated or detected from frozen food or packages, revealing the lack of effective disinfection measures in the frozen food chain and risk of transmission. We explored the possibility that disinfectant plus antifreeze could be delivered as thermal fog to realize effective disinfection at subzero temperatures. METHODS AND RESULTS: We selected two disinfectant-antifreeze combinations, didecyl dimethyl ammonium bromide (DDAB) - propylene glycol (PPG) and peracetic acid (PAA) - triethylene glycol (TEG), and each combination is used with a custom-optimized thermal fogging machine. The two fogs were tested in -20°C freezer warehouses for their disinfection efficacy against a coronavirus porcine epidemic diarrhoea virus (PEDV) field strain, a swine influenza virus (SIV) field strain, and three indicator bacteria, Escherichia coli, Staphylococcus aureus and Bacillus subtilis endospores. At -20°C, the DDAB-PPG or PAA-TEG thermal fogs settle within 3.5 to 4.5 h and effectively inactivated PEDV with median tissue culture infective dose of 10-3.5 0.1 ml-1 and SIV-H1N1 with hemagglutination titre of 26  ml-1 within 15-60 min. DDAB-PPG could inactivate S. aureus and E. coli vegetative cells (106  cfu ml-1 ) within 15-60 min but not effective on B. subtilis spores, while PAA-TEG could disinfect B. subtilis spores more effectively than for S. aureus and E. coli. CONCLUSIONS: We showed that a practical subzero temperature disinfection technology was effective in killing enveloped viruses and vegetative bacteria or bacterial spores. DDAB-PPG or PAA-TEG thermal fogging may be a practical technology for cold-chain disinfection. SIGNIFICANCE AND IMPACT OF THE STUDY: This subzero temperature disinfection technology could help to meet the urgent public health need of environmental disinfection in frozen food logistics against pandemic and other potential pathogens and to enhance national and international biosecurity.

Frozen steamed breads and boiled noodles: Quality affected by ingredients and processing.

Chinese steamed breads (CSB) and noodles are staple foods for many people. The production of frozen steamed products and boiled noodles has kept increasing. This is due to the increasing demand of ready-to-eat frozen food products from the market. Frozen storage significantly increases the self-life of the products and reduces the production costs. On the other hand, the freezing and frozen storage lead to quality loss of the frozen products. This review summarizes effects of freezing and frozen storage on diverse quality attributes (e.g., structural and textural properties) of frozen northern-type steamed breads and boiled noodles. Food safety of the frozen products related to the COVID-19 pandemic is discussed. To counteract the quality loss of the frozen products, suitable processing methods, selection of basic ingredients and uses of various food additives can be done. Research gaps to improve the textural, cooking and nutritional quality of frozen CSB and noodles are suggested.