A multi-Omic approach to food spoilage and nutritional composition within a food matrix

Porter, Kate (2022) A multi-Omic approach to food spoilage and nutritional composition within a food matrix. Doctoral thesis, Northumbria University.

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Abstract

Foods are subject to microbiological and physiochemical alterations during preparation that influence the shelf life, but the comprehensive nutritional composition of food remains unassessed. At present, food deterioration is determined using techniques based on microbial and physiochemical assessments that are both outdated and lacking sensitivity. However, advances in-Omic technologies enables a greater understanding of bacterial dynamics and spoilage mechanisms.

In this study, a novel multi-omic characterisation of spoilage in a commercially available vegetable matrix was performed. To profile spoilage the vegetable matrix was stored for 5-days under baseline condition (20 °C) and a series of conditions composing of various temperature, gas composition and pH environments. The B-vitamin composition was determined through the development of an efficient analytical method which showed excellent linearity (r 2=0.98-0.99), reproducibility (intra-day=%CV <7) and low detection (2.4-9.0 ng/mL) and quantification limits (8-30 ng/mL).

Amplicon sequencing revealed the genera Lactococcus, Leuconostoc and Yersinia were responsible for spoilage under baseline conditions. However, overall bacterial dynamics were dependent on the storage condition, for example storage in air promoted Bacillus. Storage at different temperatures 7 °C and 37 °C promoted Pseudomonas and Bacillus alongside lactic acid bacteria respectively. Amplicon sequencing was complemented with untargeted metabolite profiling of volatile and non-volatile metabolites which highlighted metabolites linked to freshness (e.g. glutathione, adenosine 5’monophosphate, arginine) or spoilage (e.g. hypoxanthine and biogenic amines). This further showed metabolic pathways such as purine, glutathione, arginine and proline metabolism were pathways involved in the spoilage of the vegetable matrix. The main volatile groups that changed during storage included, aldehydes, alkanes, alcohols, free fatty acids (FFAs), ketones and monoterpenoids. However, metabolites were shown to be dependent on microbial load and the bacterial communities present. Furthermore, this research highlighted a relationship between B-vitamins and spoilage activity. The content of riboflavin and thiamine reduced by 85.2% and 41% respectively, and nicotinamide was fully exhausted when growth of Lactococcus, Leuconostoc and Yersinia reached spoilage levels (2.105 x 108 CFU/g). This relationship was also influenced by the storage conditions, but in all conditions where growth of microorganisms reached 107-108 CFU/g, nicotinamide was depleted. Therefore, nicotinamide has the potential to be a marker of product freshness and on-going spoilage.

In conclusion, this comprehensive -Omic evaluation of food spoilage has provided novel findings regarding food spoilage dynamics that could inform future studies into food spoilage detection and shelf-life extension.

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