PENGARUH PENAMBAHAN EKSTRAK UMBI BENGKUANG (Pachyrrizus erosus) DAN UBI JALAR UNGU (Ipomoea batatas poiret) TERHADAP KUALITAS MIKROBIOLOGIS DAN VISKOSITAS YOGHURT

SATYAGUNA RAKHMATULLOH, Dr. Ir. Nurliyani, MS

2015 | Skripsi | S1 ILMU DAN INDUSTRI PETERNAKAN

Penelitian ini bertujuan untuk mengetahui pengaruh penambahan ekstrak umbi bengkuang (Pachyrrizus erosus) dan ubi jalar ungu (Ipomoea batatas poiret) pada yoghurt probiotik terhadap kualitas mikrobiologis, dan fisik. Yoghurt dibuat dari susu segar, susu skim sebesar 5% (b/v) dengan penambahan ekstrak umbi bengkuang dan ubi jalar ungu sebesar 10% (v/v) serta tanpa ekstrak sebagai yoghurt kontrol, kemudian diinokulasi dengan Streptococcus thermophillus, Lactobacillus bulgaricus, dan bakteri probiotik Lactobacillus casei subsp rhamnosus, sebanyak 3% (v/v). Kualitas mikrobiologis yang diuji meliputi total bakteri asam laktat (BAL), total probiotik, dan daya hambat terhadap bakteri En-teropathogenic Eschericia coli (EPEC), kualitas kimia yang diuji meliputi kadar keasaman dan nilai pH, sedangkan kualitas fisik yaitu viskositas. Hasil penelitian menunjukkan bahwa terdapat perbedaan yang nyata (P<0,05) total BAL antara yoghurt dan yoghurt probiotik. Rerata total BAL pada yoghurt 10,04±0,33 log cfu/ml, sedangkan pada yoghurt probiotik sebesar 9,59±0,49 log cfu/ml. Penambahan ektrak umbi bengkuang dan ubi jalar ungu memberikan pengaruh yang nyata (P<0,05) pada kadar keasaman. Rerata daya hambat yoghurt dan yoghurt probiotik terdapat perbedaan yang signifikan (P<0,05). Rerata daya hambat yoghurt dan yoghurt probiotik sebesar 1,87±0,12 mm dan 1,13±0,09 mm terhadap EPEC. Tidak terdapat perbedaan pada viskositas yoghurt. Rerata viskositas yoghurt tanpa penambahan ekstrak, penambahan 10% ekstrak umbi bengkuang, dan 10% ubi jalar ungu berturut-turut sebesar 1.646,2±614,0; 1.489,2±515,5; dan 1.218,3±1.155,0 cP. Penambahan ekstrak umbi bengkuang dan ubi jalar ungu dapat meningkatkan keasaman. Yoghurt tanpa penambahan Lactobacillus rhamnosus mampu menghambat bakteri EPEC yang lebih besar. Kata kunci : Yoghurt, Umbi bengkuang, Ubi jalar ungu, Lactobacillus casei subsp rhamnosus, Antibakteri EPEC

This study aimed to determine the effect of extracts of yam tuber (Pachyrrizus erosus) and purple sweet potato (Ipomoea batatas poiret) in the probiotic yoghurt against microbiological and physical quality. Yoghurt made of fresh milk, skim milk 5% (w/v) with the addition of yam tuber extract and purple sweet potato 10% (v/v) and without extract as yogurt control, then it was inoculated by Streptococcus thermophillus, Lactobacillus bulgaricus, and probiotic Lactobacillus casei subsp rhamnosus 3% (v/v). Microbiological quality tested a total lactic acid bacte-ria (LAB), total of probiotics, and inhibition against Enteropathogenic Escherichia coli (EPEC). The chemicals quality test were acidity and pH values, and also physical quality test was viscosity. The results show that there were significant differences (P<0.05) between the total LAB probiotic yoghurt and yoghurt. The mean of LAB total of yoghurt was 10.04±0.33 log cfu/ml, the probiotic yoghurt was 9.59±0.49 log cfu/ml. The addition of yam tuber extract and purple sweet potato significant (P<0.05) in the acidity. The mean of inhibition of yoghurt and probiotic yoghurt were no significant differences (P<0.05). The mean of inhibition of yoghurt and probiotic yoghurt for 1.87±0.12 mm and 1.13±0.09 mm on EPEC. There were no differences in the viscosity of yoghurt. The mean of viscosity of yogurt without the addition of the extract, the addition of yam tuber extract 10%, and 10% purple sweet potato were of 1646.2±614.0, 1489.2±515.5, and 1218.3±1155.0 cP. The addition of yam tuber extract and purple sweet potatoes could increse levels of acidity. Yogurt without addition of Lactobacillus rhamnosus bacteria could inhibit EPEC. Keywords: Yoghurt, Tubers yam, Purple sweet potato, Lactobacillus casei subsp rhamnosus, Antibacterial EPEC.

Kata Kunci : Yoghurt, Umbi bengkuang, Ubi jalar ungu, Lactobacillus casei subsp rhamnosus, Antibakteri EPEC