Identification and characterization of beneficial microbiota in beef biltong from Namibia Central regions
Loading...
Date
2017
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Namibia
Abstract
Microbiota associated with beef biltong has not been assessed in Namibia and there is limited data in the literature describing the presence and role of lactic acid bacteria (LAB) in biltong products which is involved in the transformation of many aroma and flavour compounds and therefore, the quality of the final product. The aims of this study were to document the steps involved in beef biltong production, determine the physicochemical parameters that may influence microbial growth, characterize and identify LAB, yeast and moulds associated with beef biltong and, profiling LAB isolates for enzymatic and bacteriocin activities. Beef biltong is produced by a dry curing process. Its average pH ranged from 5.1±0.15 to 5.98±0.16, average sodium chloride content ranged from 3.16±0.62 to 3.98±0.86 g/100g, the average moisture content ranged from 7.56±7.56% to 18.86±8.96% and average water activity (aw) ranged from 0.79±0.05 to 0.84±0.06. Beef biltong samples from Otjozondjupa, Omaheke and Khomas regions were characterized with an average total plate count ranging from 5.4±0.36 to 6.46±0.36 log CFU/g, average total LAB ranging from 5.66±0.41 to 7.02±0.35 log CFU/g while average total yeast and moulds ranged from 5.25±0.78 to 6.14±0.14 log CFU/g. Yeasts associated with beef biltong were identified as Candida zeylanoides, C. guilliermondii, C. famata, C. krusei, C. tropicalis, Meyerozyma guiliermondii and Yarrowia lipolytica using API 20 C AUX and sequencing of the 26S rRNA and ITS genes. The LAB were identified using API 50CHL and sequencing of the 16S rRNA as: Lactobacillus brevis, L. graminis, L. plantarum, L. pentosus, L. paraplantarum, Lactococcus lactis ssp. lactis, Leuconostoc mesenteroides ssp. mesenteroides, Pediococcus acidilactici, P. pentosaceus, Weisella cibaria, and W. confusa, The cell free supernatant (CFS) of LAB was found to exhibit a variable degree of antimicrobial activity by agar well diffusion method against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Clostridium perfringens, Candida albicans and Aspergillus niger. After pH neutralization of the CFS, the antimicrobial activity due to bacteriocin or bacteriocin-like substances was detected in L. plantarum against B. subtilis, C. albicans and A. niger. Enzymatic activities detected in LAB using API ZYM included esterase, lipase, valine arylamidase, cysteine arylamidase, acid phosphatase, leucine arylamidase and β galactosidase. Beef biltong samples were associated with beneficial yeast with applications in food industries, as well as LAB with biotechnological properties such as enzymatic activity and bacteriocin production. Therefore, these strains may be important to be used as starter cultures to improve the quality and safety of meat products.
Description
A thesis submitted in partial fulfilment of the requirements for the Master of Science (Food Microbiology)
Keywords
Microbiota, Beef biltong