Micro-organisms: spoilage

Most concentrated beverages contain fruit juice or whole fruit , a term that refers to a comminuted form of citius that includes components of juice, essential oil, peel (flavedo) and pith (albedo). Concentrated soft drinks are usually flash-pasteurised and chemically preserved. Their dilutable form means that they are often held in partially filled bottles for significant lengths of time (often many weeks or even months) and are extremely vulnerable to spoilage by micro-organisms. 

If juice is to be sold as not from concentrate it is usually screened and pasteurised immediately after pressing - an operation with two main objectives. The first is to control the growth of spoilage micro-organisms that live on the fruit surface (mainly yeasts and moulds). The second is to destroy the pectolytic enzymes that occur naturally in fruit that would otherwise break down the cloudy nature of the juice. If, however, a clear juice is required (e.g. apple or raspberry), enzymes can be added to accelerate this natural process. 

Banerjee, M. and Sarkar, RK. 2004. Antibiotic resistance and susceptibility to some food preservative measures of spoilage and pathogenic micro-organisms from spices. Food Microbiology 21 335-342. 

It is difficult to be specific about microbial damage in fruit and vegetables because there is usually a succession of micro-organisms and each commodity will differ. However, numerous different types of spoilage can be recognised. 

Sagoo S., Board R., RoUer S., 2002. Chitosan inhibits growth of spoilage micro-organisms in chilled pork products. Food Microbiol. 19 175-182. 

Harrison, 1., Webb, T. J. B., Martin, P. A. (1974). The rapid detection of brewery spoilage micro-organisms. Journal of the Institute of Brewing, 80(4), 390-398. 

Mejlholm O, Dalgaard P (2002) Antimicrobial effect of essential oils on the seafood spoilage micro-organism Photobacterium phosphoreum in liquid media and fish products. Lett Appl... 

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