Effects of antibacterial substances in aloe vera gel to the growth of lactic acid bacteria in yoghurt
1997
Chongkolnee Waeohongsa
Optimal formula for yoghurt production was 40 percent fresh milk, 12 percent skin milk powder, 0.1 percent gelatin and 46 percent water. The optimal starter was 3 percent freeze-dried lactic culture type B-58. The mixture was incubated at 43 deg C for 6-8 hours. Fresh and processed aloe vera had no effects to the growth of lactic acid bacteria. Sensory evaluation by Response Surface Method (RSM) showed that the suitable amount of aloe vera and sugar for yoghurt production was 13 percent and 7 percent, respectively. The aloe vera yoghurt had L, a and b values 93.30, 8.20 and 38.20, respectively. Its syneresis was 30.12 percent and viscosity was 4280.00 centipoises. The final pH was 4.2 and lactic acid yield was 1.29 percent. It contains 84.49 percent total solid, 15.51 percent moisture, 12.85 percent protein, 2.35 percent fat, 1.35 percent ash, 0.03 percent crude fiber, 67.91 percent carbohydrate and 6.67 percent lactose. The vitamin A and D content were 96.00 and 226.94 IU/100 g respectively. It had 2.35 g/kg calcium and 0.11 percent chloride. Lactic acid bacteria count and total cell count were 1.68*10*[9) and 1.53*10*[9) cfu/g respectively. Coliform bacteria was less than 3 MPN/100 g while yeast and mold were not found. The aloe vera yoghurt was stored at 4 deg C for 30 days. After 15 days, L value, b value, pH and lactic acid yield were significantly difference from initial product. The a value, lactic acid bacteria count and total cell count were not significantly difference from the initial product. The coliform bacteria was 3 MPN/g in initial product and decreased to less than 3 MPN/g after 9 days. While Salmonella sp., Listeria sp., Staphylococcus sp., yeast and mold were not found during storage time. The trained panels accepted the yoghurt when it was stored for 18 days while consumers accepted it before 24 days. Consumers liked this product moderately to like strongly.
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