Application Of Lactic Acid Bacteria L.Casei Zhang And L.Plantarum IMAU10120in Yoghurt Used As Preservative Culture

The application of LAB used as preservative culture provides a new direction for extending shelf-life time of yoghurt. LAB can not only keep yoghurt fresh by inhibiting growing of yeasts and moulds, but also enhance its security along with health promoting effect. In the present study, L. casei Zhang and L. plantarum IMAU10120were enrolled for evaluating fermented characteristics and storage stability of yoghurt compared with commercial preservative culture in order to check whether these two strains possess the potential preservative ability. At the same time, the inhibitory extent on yeasts and moulds by the commercial strains also been investigated which provided basic data for the development of preservative culture. The results were showed as follows:(1) Adding of L. casei Zhang (3.0×106cfu/mL) or L. plantarum IMAU10120(3.0×106cfu/mL) could shorten the fermentation time to different levels, and the combined of both (1.2×106+1.2×106cfu/mL) effectively weakened the postacidification of samples. L. casei Zhang (2.4×106～3.0×106cfu/mL) inhibited the yeasts and moulds to some degree during fementation, and the inhibition to yeasts was much more outstanding. During the storage period, L. plantarum IMAU10120(2.4×106～3.0×106cfu/mL) could decrease the counts of yeasts and moulds significantly. Meanwhile, the combined strains of L. casei Zhang and L. plantarum IMAU10120(1.5×06+1.5×106cfu/mL Mnhibited the yeasts or moulds of yoghurt most significantly both in fermentation and storage time.(2) No significant effect was observed in commercial preservative culture A with inhibiting variable concentrations of yeasts and moulds. But commercial preservative culture B showed a favorable inhibitory effect on yeasts and moulds respectively with a dose of5.24cfu/mL and32cfu/mL. During the storage period, neither of two commercial preservative cultures showed a notable result in inhibiting different concentrations of yeasts. However, commercial preservative culture A significantly restrained the moulds with a adding dose of3.2cfu/mL.(3) The verification test indicated that L. casei Zhang combined with L. plantarum IMAU10120(1.5×106+1.5×106cfu/mL)could prepare a refreshing yoghurt characterized by inhibiting the yeasts and moulds during storage, suggesting they possessed excellent potential characteristics used as preservative culture.