Variation in heat resistance of Clostridium sporogenes spores in oils and oil-water systems: Insights from oil physicochemical properties and spore surface properties

Abstract

Our recent research found that oil could greatly improve the heat resistance of Clostridium sporogenes spores in liquid foods. To figure out the key factors influencing the spore heat resistance, we characterized the heat resistance of C. sporogenes CICC 8021 spores in three pure edible oils (rapeseed oil, peanut oil, and palm oil) and their oil-water systems and analyzed their relations with the oil's physicochemical properties and spore surface properties. The results showed that in pure oils, the water activity (a_w) of oil is significantly negatively related to spore heat resistance (P < 0.05). In the oil-water systems, the distribution of the spores was affected by the addition level of peanut and palm oils, but not applied to rapeseed oil. In the low-oil system (10 % peanut oil-water system), the spore hydrophobicity increased during heating, causing the spores to migrate to the oil phase and thus increasing spore heat resistance. In the high-oil system (50 % peanut oil-water system), the increase of the spore's ζ-potential during heating was the key factor for the spore heat resistance. The interfacial tension of peanut oil decreased at the elevated temperature, facilitating the adsorption of the spores at the oil-water interface and their entrance to the oil phase, and this is worth further exploration. This study provides a novel interpretation of oil physicochemical properties and spore surface characteristics on the heat resistance of C. sporogenes spores in oils and oil-water systems, offering valuable insights for exploring the mechanism of spore resistance in liquid foods with oils.