| Thermal processing was the most common treatment during canned foods production. Intensely thermal process was usually used to sterilize canned food which was prone to be contaminated by thermophilic but high temperature resistance microorganism. However, intense sterilization processing would induce deterioration of quality in the color and the texture, loss of nutrition and increase the energy cost. In this study, the effect of main environmental stresses on the thermal resistance of Bacillus Stearothermophilus spores was investigated, which were pH values, food ingredients, selected synthetic antiseptic, natural bacteriostat. Moreover, the synergic effects between various food ingredients and Nisin on the thermal resistance of Bacillus Stearothermophilus spores were also probed.Initially, effects of different pH values, concentration of sodium chloride, whey protein and sucrose on the thermal resistance of Bacillus Stearothermophilus spores were conducted. Meanwhile, synergic effects of sucrose or whey protein with different pH,10% sucrose with different concentration of salt and sucrose with whey protein on the thermal resistance of Bacillus Stearothermophilus spores were also estimated. The results demonstrated that pH had significant ly affect the thermal resistance of spore, namely D value reduced and Z value increased when pH decreased. Whey protein exhibited protecting for spore from thermal treatment at the temperature of 115℃and 118℃, whereas whey protein did not work at the temperature of 121℃. No significant effect on the thermal resistance of spore was detected by sodium chlorine within the concentration of 8% at the temperature of 115℃, but the thermal resistance of spore was decreased by sodium chlorine at the concentration of 4-8% at the temperature of 118℃and 121℃. Sucrose showed protective effect on the thermal resistance of spore only at the concentration of 10%. Both sucrose at the concentration of 10% and whey protein at the concentration of 8% did not increase the thermal resistance of spore at the low pH values of 3.0 and 4.0. Combination of sucrose and whey protein indicated relatively high synergic effect on the thermal resistance of spore during sterilization, which leading to remarkably enhance the thermal resistance of spore.On the other hand, the effects of potassium sorbate, Epigallocatechin gallate (EGCG), sodium lactate, Nisin, sucrose esters or lecithin, and their synergic effects of sucrose or whey protein plus Nisin on the thermal resistance of Bacillus Stearothermophilus spores were systematically investigated, respectively. EGCG at the concentration of 0.4 mg/mL and sodium lactate at the concentration of 4% had no significant effect on the thermal resistance of spore. Nisin was capable of remarkably decreasing the D value of spore. Besides, Nisin also exerted promoted significant reduction on the thermal resistance of the spore (Z value) as its concentration increased. D value of spore was caused decreasing by potassium sorbate, whereas changes of Z value were limited to its type but not concentration, and was less effective than Nisin. Unfortunately, sodium benzoate has no effect to the thermal resistance. The similar effects on the thermal resistance of spore causing by sucrose ester and lecithin were also observed. The result implied that any each of them did not induce remarkably decreasing the thermal resistance of spore; however D value can be effectively decreased in the emulsion system via addition of other ingredients, such as milk. Interestingly, whey protein can impair the effect of D value with Nisin on thermal properties of Bacillus Stearothermophilus, whereas sucrose reduced Z value but not D value which caused by Nisin.Compared the blank, the thermal resistance and sterilization time of spore were dramatically reduced under 115 oC treatment when Nisin concentration at 0.2 mg/ml added to the broth.Overall, among various factors that affecting thermal resistance of Bacillus Stearothermophilus spores, the current work suggests pH values were critical to the aforementioned properties of spores based on comparing with different food ingredients (e.g., sugar, protein, and mineral as well). Protein and inorganic matter subsequently indicated effectiveness on the thermal resistance of Bacillus stearothermophilus spores. In other words, small molecular like mineral salts were seemly ineffective. As for the inhibiting bacterial, natural bacteriostat Nisin was the most effective additive, whereas potassium sorbate taken second palace. Polyphenol and sodium lactate were lowest effective. Noticeably, the sterilizing process and intensity were also playing an important role in the canned foods sterilization. Our results present a rational consideration for canned foods production.
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