RESPONSE OF LACTIC ACID BACTERIA TO ZINC SALTS USABLE FOR SUPPLEMENTATION OF FERMENTED MILK AND MILK-BASED PRODUCTS

Zinc is a trace mineral that is essential for a multitude of basic physiological functions in humans. The human body has a limited capacity of storing zinc and zinc deficiency can develop rapidly when intakes are low. Due to the massive number of zinc-dependent biological processes and interactions, zinc deficiency has serious implication on human health. Poverty, limited food availability and food preferences are some of the factors that contribute to risk of zinc deficiency. There is a wide variety of zinc food sources available naturally. Milk and dairy products contain ~ 1.2 mg/100 g of zinc and provide ~ 20% of the Recommended Dietary Allowance. Milk may also be used as a vehicle for zinc fortification or as an ingredient in supplemented foods. Zinc naturally occurring in milk is unlikely to have an inhibitory effect on lactic acid bacteria (LAB), which spontaneously occur in raw milk or may be added as selected starter cultures for the manufacture of fermented dairy products. However very scarce information are available on the comparative response of this microbial group to different zinc salts usable for supplementation of fermented milk and milk-based products. Accordingly, the present research work was aimed at assessing the effect of three zinc salts on the acidifying activity of 108 LAB ascribed to species of dairy interest. Supplemented skimmed-milk with 250 ppm of zinc sulphate, zinc gluconate, and zinc aspartate was inoculated with each active culture, incubated at the opportune conditions, and subjected to pH measurement after 6 and 24 h of fermentation. Statistical elaboration of data was performed in order to assess the response (inhibition, stimulation or no effect) of these LAB cultures to the three zinc salts considered. II.02 – GESTIONE DELLO STRESS IDRICO IN TAPPETI ERBOSI DI CYNODON