Effect of irrigation and lactic acid bacteria inoculants on the phenolic fraction,fermentation and sensory characteristics of olive (Olea europaea L. cv. Ascolana tenera) fruits

Plant productivity, phenolic profile and natural fermentation, with and without lactic acid bacteria inoculants, were investigated in olive fruit of Ascolana tenera growing under different irrigation regimes. A rainfed control and two treatments receiving a water depth equivalent to 33 and 66% of the estimated crop evapotranspiration (ETc) from the pit hardening stage and a treatment with 66% of ETc during the entire season (25 May‐4 October), were tested. Olive vigour increased with irrigation, which also induced a fresh yield enhancement, mainly due to the increase in fruit size. The differences between treatments were less evident for fruit number per tree and pulp/stone ratio. The phenolic content increased in water deficit‐stressed olives and differences were detected in the concentrations of individual phenolic compounds. Olive oil content and fatty acids composition appeared scarcely affected by irrigation. Values of pH, acidity, sugars, phenolic composition and microbial population were monitored during olive fermentation. Extracts of freshly harvested olive fruits exhibited significantly higher phenolic content than extracts of processed olives. The interaction of irrigation and fermentation appeared to have a significant effect on the chemical and sensory characteristics of the end product. The bitter taste of olive fruit was positively correlated with the level of total phenolics, but negatively correlated with the overall acceptability for direct consumption. The fermentation process was accelerated in the presence of lactic acid bacteria inoculants, indicating the potential use of these microorganisms as quality control markers in table olives during processing. Copyright © 2006 Society of Chemical Industry     

Study of the effects of temperature, pH and NaCl on the peptidase activities of non-starter lactic acid bacteria (NSLAB) by quadratic response surface methodology

The individual and interactive effects of temperature, pH and NaCl on the aminopeptidase-types N and A and proline iminopeptidase activities of several strains of non-starter lactic acid bacteria (NSLAB) were studied by quadratic response surface methodology. The effects on enzyme activities depended on the interactions among the independent variables, species, strains within species and type of activity. With few exceptions, the aminopeptidases N and A and proline iminopeptidase activities of Lactobacillus casei ssp. pseudoplantarum and Lb. curvatus were strongly inhibited by the hostile cheese-like conditions, while the peptidases of Lb. casei ssp. casei and especially Lb. plantarum were tolerant or not affected by variations in pH and showed the least sensitivity to NaCl or even a requirement for NaCl for the optimal activity. Strains which maintained relatively high activity under cheese-like conditions were selected within the species. The proline iminopeptidase of Lb. casei ssp. casei 2107 as well as Lb. plantarum 2788 and 2789 greatly tolerated the interactions among the independent variables. At 10°C in the presence of 3.750% NaCl and independent of the pH, the PepN activity of Lb. plantarum 2788 and 2789 was at least 33% of the maximum determined at pH 7.5 and 35°C. Proline iminopeptidase activity was most sensitive to the individual and interactive variations in temperature, pH and NaCl. On the other hand, aminopeptidase-type A activity seemed to be least sensitive to cheese-like conditions.