Abstract
Yellow alkaline noodle (YAN) is very susceptible to spoilage and has a short shelf life due to the high moisture content. This study was conducted to isolate and identify spoilage bacteria of YAN in an attempt to apply local plant extracts that possess antibacterial activity in extending the shelf life of YAN. Thirty colonies were isolated from spoiled YAN and were identified using the Biolog GEN III system. Eight bacteria which consisted of five Gram-positive (GP) and three Gram-negative (GN) (Bacillus pumilus, Clavibacter agropyri, Corynebacterium urealyticum, Corynebacterium jeikeium, Enterobacter cloaceae, Pseudomonas aeruginosa, Serratia marcescens and Staphylococcus sciuri) were identified. E. cloaceae and S. sciuri were the most abundant bacteria on YAN with percentage values of 23 and 26%, respectively. The antibacterial activities of ethanol and water extracts of six types of leaves (Centella asiatica, Jasminum sambac, Pereskia bleo, Cosmos caudatus caudatus, Murraya koenigii, and Melicope lunu) against all the identified bacteria were studied. The ethanol extracts of M. koenigii are most effective extract that possess the highest antibacterial activity against all the eight spoilage bacteria studied.
Highlights
Yellow alkaline noodle (YAN) is one of the popular food in Malaysia, Indonesia and Singapore
They comprised of five GP bacteria which were Bacillus pumilus, C. agropyri, C. urealyticum, C. jeikeium, S. sciuri and three GN bacteria which were E. cloaceae, P. aeruginosa, S. marcescens
The least dominant spoilage bacteria found in YAN were S. marcescens and C. urealyticum with similarity index of 0.58 and 0.75 and at probability of 94 and 99%, respectively
Summary
Yellow alkaline noodle (YAN) is one of the popular food in Malaysia, Indonesia and Singapore. The addition of alkaline salt confers a unique flavor and quality of YAN, which is absent in pasta or other type of noodles. Besides producing noodles with a pH range of 9.0 to 10.0, microbial or fungal growth causes development of sliminess on the surface of noodles at this pH range. Yellow alkaline noodles are partially boiled wet noodles with moisture content of 50 to 60% (Karim, 1989), they are very susceptible to spoilage and have a shelf life of 1 to 1.5 days. According to Ray (2001) the highest incidence of spoilage in processed foods is caused by bacteria followed by yeast and moulds
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