Publication: Effects of Incorporation of Lactic Acid Bacteria on Microbiological Quality and Shelf Life of Raw 'Satar'
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Date
2015
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Publisher
Springer
Abstract
Maintaining a safe food supply has become an ever-changing endeavour as some emerging pathogens are discovered. Relying on traditional methods of thermal processing to create microbiologically safe foods is not sufficient. Research on finding other methods of controlling the growth and multiplication of pathogenic and spoilage bacteria needs to be explored. The use of crude bacteriocin produced by lactic acid bacteria may be one promising solution of controlling microbial growth in ready-to-eat (RTE) foods. The ability of lactic acid bacteria (LAB) to produce metabolites with broad-spectrum inhibitory activity that are heat stable is an important criterion for the application of LAB as preservative in food. 'Satar' was used as a model for this study because it is highly perishable and has a short shelf life (<12 h) at ambient temperature and, therefore, is unable to be stored for a long period of time. This chapter briefly describes the background of 'Satar' and its relations to microbiological safety. The study focused on choosing the suitable strains of LAB, identifying the isolates phenotypically using biochemical tests and VITEK 2 Compact System. The isolates were tested on their ability to inhibit LAB microflora, ability to inhibit a broad spectrum of Gram-negative and Gram-positive bacteria and ability to exhibit the antimicrobial activity after being subjected to heating temperatures. Among nine isolates of LAB from fermented fish, supernatants of four isolates were studied extensively for their heat stability at different heating temperatures (70, 80, 90, 100 and 121 degrees C) and heating times (5 and 20 min). Two strains, Lb. acidophilus and Lb. plantarum, were chosen for the incorporation of their crude bacteriocin in raw ' Satar', and their characteristics and microbiological shelf life were evaluated. Incorporation of crude bacteriocin of Lb. acidophilus and Lb. plantarum at 3 % and 6 % did not significantly affect (P>0.05) the water activity and pH, but significantly increased the moisture content when Satar was stored more than 20 h at ambient temperature. There was no significant difference (P>0.05) for a* value and b* value of 'Satar' among all samples at 0 h of storage time, except after 3 h of storage at ambient temperature. The colour analysis of samples showed a range of colour between grey and light grey. The incorporation of 3 % and 6 % crude bacteriocin of Lb. acidophilus and Lb. plantarum in raw ' Satar' could extend the shelf life from 8 h to 20 h and 17 h, respectively. This study has proven that LAB can be used to extend the shelf life of ready-to-eat food.