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Abstract

Optimization of composition of Lactobacillus bulgaricus and Streptococcus thermophilus in yoghurt fortified by lakum fruit (Cayratia trifolia (L.) Domin) extract as an antibacterial against Escherichia coli was investigated for the first time in this research. Yoghurt was made by fermenting milk with several compositions of L. bulgaricus and S. thermophilus as starter cultures and also adding lakum fruit extract as an antibacterial against E. coli. The fermentation process was depended on the bacterial culture used. The aim of the research was to determine the optimal composition of L. Bulgaricus and S. thermophilus bacteria in lakum fruit yoghurt as an antibacterial against E. coli. The research was done by making variation of composition of L. bulgaricus and S. thermophilus bacteria culture in lakum fruit yoghurt. Lakum fruit yoghurt was analysed with acidity stability test, pH, anthocyanin level and inhibitory activity against E. coli. The data analysis was done with MANOVA (Multivariate Analysis of Variance). The results showed that lakum fruit yoghurt with composition of L. bulgaricus and S. thermophilus 2:1 (v/v) had a good stability with increased acidity dan decreased pH. The value of anthocyanin in lakum fruit yogurt decreased and plain yoghurt (without lakum fruit extract) with composition of L. bulgaricus and S. thermophilus 2:1 (v/v) gave the highest inhibitory value against E. coli.

Bahasa Abstract

Optimasi komposisi Lactobacillus bulgaricus dan Streptococcus thermophilus pada yogurt terfortifikasi buah lakum (Cayratia trifolia (L.) Domin) sebagai antibakteri terhadap Escherichia coli telah dilakukan. Yogurt dibuat dengan memfermentasikan susu bubuk full cream dengan penambahan variasi kultur bakteri L. bulgaricus dan S. thermophilus, serta penambahan ekstrak buah lakum. Proses fermentasi sangat bergantung pada kultur bakteri yang digunakan. Penelitian ini bertujuan untuk mengetahui komposisi optimal bakteri L. bulgaricus dan S. thermophilus pada yogurt terfortifikasi buah lakum sebagai antibakteri pada E. coli. Penelitian dilakukan dengan cara memvariasikan komposisi bakteri L. bulgaricus dan S. thermophilus pada yogurt buah lakum. Analisis terhadap yogurt buah lakum dilakukan dengan pengujian stabilitas keasaman, pH, kadar antosianin dan aktivitas daya hambat terhadap bakteri E.coli. Analisis data dilakukan dengan menggunakan MANOVA (Multivariate Analysis of Variance). Hasil penelitian menunjukan bahwa yogurt buah lakum dengan kombinasi L. bulgaricus dan S. thermophilus 2:1 (v/v) memberikan stabilitas yang baik selama penyimpanan dengan nilai keasaman yang meningkat dan pH yang turun. Kadar antosianin dalam yogurt selama penyimpanan mengalami penurunan dan yogurt plain (tanpa penambahan ekstrak buah lakum) dengan kombinasi L. bulgaricus dan S. thermophilus 2:1 (v/v) memiliki daya hambat terhadap bakteri E. coli dengan nilai yang paling tinggi.

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