Herbal tea is known rich in bioactive compounds and pigments. Herbal tea can be derived from Butterfly pea flowers. Butterfly pea has a high level of anthocyanins and flavonoid levels. However, butterfly pea has not been used optimally in fermentation products such as water kefir. Water kefir has many benefits and potential antioxidant sources. This research aimed to optimize fermentation time (24-48 hours) and concentration grain (5-15%) for the production of butterfly pea water kefir with a good antioxidant activity using response surface methodology. Central Composite Design was used to develop models of the response. The response used in this research is antioxidant activity, flavonoid, anthocyanin and brightness. The optimum condition was obtained at 36 hours 2 minutes of fermentation time, and 15% of grain concentration using Design Expert 10.01. The optimum combination for butterfly pea water kefir resulted in 58 ppm of antioxidant activity, 39 of brightness, 81 mg/g QE of flavonoid and 4.2 ppm of anthocyanin. A validation experiment showed that no significant difference between actual and predicted values based on paired t-test (p>0.05) using Minitab 17.0.

Kefir adalah susu fermentasi dengan aroma yeasty. Kefir diproses melalui susu pasteurisasi menggunakan starter biji kefir. Tujuan penelitian ini untuk mengetahui pengaruh suhu dan lama penyimpanan terhadap kadar alkohol kefir susu sapi. Metode penelitian yang digunakan adalah Rancangan Acak Kelompok Faktorial dengan dua faktor dan tiga level. Faktor yang digunakan adalah lama penyimpanan selama 7, 14 , dan 21 hari serta suhu penyimpanan pembekuan(-10°C), pendinginan (15°C), dan suhu ruang (20°C). Analisis menggunakan ANNOVA, uji lanjut DMRT 95%, Zeleny. Hasil menunjukkan bahwa adanya interaksi antara lama penyimpanan dengan suhu penyimpanan yang nyata (α = 0.05). Hasil perlakuan terbaik adalah penyimpanan suhu (-10°C) hari ke 7 dengan karakteristik pH sebesar 4.47 , TPT sebesar 10.00 %Brix, total gula sebesar 3.07%, total asam sebesar 0.26%, kadar alkohol sebesar 0.04%, total bakteri asam laktat sebesar 5.91 Log CFU/ml dan total khamir sebesar 6.56 Log CFU/ml

Kefir is an acidic-alcoholic fermented milk product with little acidic taste and creamy consistency and has a distinctive yeasty aroma. Bacteria in the grain produce lactic acid and flavor components, carbon dioxide, and alcohol. Increased alcohol levels can occur with longer storage. The optimal temperature for the growth of alcohol-producing microorganisms can be at room temperature, whereas low temperatures can inhibit microbial growth and biochemical processes. This study aimed to determine the effect of temperature and storage time on the alcohol content of cow milk kefir. The research method used Randomized Block Design Factorial with two factors and three levels. The first factor was the storage time that consists of 7, 14 and 21 days. While, the second factor was storage temperature that consists of freezing storage (-10°C), refrigerator storage (15°C), and room storage (20°C). Data were analysed using ANOVA, then the further test DMRT with a 95% confidence interval. The best treatment result was tested using Zeleny. The best treatment result was attributed to freezing storage (day 7) at -10°C, with physical parameters include pH of 4.47 and total soluble solids of 10.00% Brix. Then, chemical parameters are total sugar (3.07%), total acid (0.26%), and alcohol content (0.04%). Lastly, microbiological parameters include the total of lactic acid bacteria (5.91 Log CFU/ml) and the total of yeast (6.56 Log CFU/ml). Kefir with the best treatment could decrease the alcohol level and safe for consumption.