Nitrogen-Nanobubble technology to improve the shelf-life of fish : A dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Food Innovation at Lincoln University

Abstract

Freshness and quality of fish is a critical issue of concern in international fishery industry. Although various techniques in preservation has introduced over years, a safe, economic and sustainable approach is significant to meet consumers demand and to alleviate the issues faced by fishery trade. Nitrogen -nanobubble technology in combination with refrigeration is an approach that can be considered as a sustainable and safe preservation technique that is capable of eventually replacing todays expensive, synthetic and artificial preservatives. Nanobubble technology with nitrogen gas has anti-microbial effect with the release of free radicals when they collapse, besides nitrogen replaces dissolved oxygen and creates an anaerobic environment during treatment which controls microbial activity and its growth. The current study is concentrated on this aspect of nitrogen nanobubble technology to extend the shelf life of salmon fish fillet. Two fillets were taken, and each fish fillet was portioned to 3 parts- for treating with nitrogen nanobubble treated RO water, other one with untreated RO water and third portion for refrigeration alone. After proposed treatments, fillets were refrigerated at 4⁰C for microbial analysis at different storage days such as 0, 3, 6 and 9. Microbial analysis was performed on respective days to enumerate total aerobic viable count, total anaerobic count, total coliform counts, psychrotrophic counts and H2S producing bacterial count. Generation time of aerobic and anaerobic bacterial counts were analysed to assess the influence of different treatments on bacterial colony generation and the average time taken to generate the colonies. Results obtained from analysing microbial count as well as generation time, provides positive results favouring the present research work. However, the study had limitations such as variations in bacterial count between replicates, hence future research work is recommended on the promising preservation technology – Nitrogen nanobubble treatment in combination with refrigeration.