Production of Functional Yogurt: Effect of Natural Antioxidant from Guava (psidium Guajava) Leaf Extract

The possibility of producing a functional yogurt from a skimmed buffalo ' s milk using guava (Psidium guajava) leaf extract was investigated. Methanol exhibited slightly higher extraction ability for phenolic compounds than ethanol and water. The total phenols were 894, 882 and 877μg/g powder, respectively, when extraction ratio was 1:12. Addition of water extract of guava leaf by different concentrations to a functional yogurt, showed significant changes of pH, titratable acidity during cold storage up to 5 days. The reducing activity of all samples significantly (P>0.05) decreased up to the end of storage period , while the inhibition of ascorbate autoxidation significantly increased with increasing of the amount of phenolic compounds till 300 μg phenolic components /100ml yogurt followed by a slight decrease. During storage, the average viable cell counts on MRS increased in yogurt contained guava leaf extract 75 μg phenolic component /100ml from log CFU/ml 9.60 after one day to 10.17 on day 5. Notwithstanding, there was a decline in log CFU/ml on M17 throughout storage. Sensory evaluation data indicated no significant differences (P>0.05) between the control and treated samples. Based on the above results, technology can be proposed for productions of a functional yogurt with water extract of guava leaf, as natural antioxidant source. J.Agric.&Env.Sci.Alex.Univ.,Egypt Vol.8 (1)2009 201