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In this study, various kinds of cryoprotectant (skim milk, lactose, and sucrose) formulations were tested to enhance the survival of Lactobacillus brevis ED25 after freezing and freeze‐drying. A Box–Behnken experimental design was used to optimize cryoprotective medium and the highest cell survival was observed with the 17.28% skim milk, 2.12% lactose, and 10% sucrose cryoprotectant as the optimum condition. The structural and physicochemical characteristics of freeze‐dried powder were acceptable for application with regards to particle surface morphology, moisture and water activity (Aw), glass transition temperature (Tg), Fourier transform infrared spectra, X‐ray structure, and also storage stability under the refrigeration and room temperature conditions. Accelerated storage test based on Arrhenius equation could be used to predict the freeze‐dried bacterial shelf life but only with a certain degree of predictability for long‐term storage. The acidification kinetics of fresh and stored culture in sourdough fermentation was also described on the basis of the Gompertz equation. Practical applications: Freezing and storage are crucial factors for the viability and acidification power of starter culture. Therefore, various types and concentrations of cryoprotectants have been used to preserve the microorganisms. L. brevis ED25 has been a good potential for the manufacture of industrial sourdoughs and this research has aimed to investigate long‐term protective effects of optimum cryoprotectant formulations on the viability of bacteria and also determine the acidification power in sourdough. The results showed the potential value of freeze‐dried L. brevis ED25 culture for commercialization. [ABSTRACT FROM AUTHOR]

The aim of this work was to study the influence of temperature (85, 90, 95 and 100 °C), total soluble solids (SS: 10 and 20°Brix or % by weight of sucrose) and pH (3.5 and 4.0) on decimal reduction time ( D-value) of the Alicyclobacillus acidoterrestris strain DSM2498 spores in apple juice, orange juice and malt extract broth (MEB). The effects of SS and pH on D-values and z-values in each media were insignificant ( P > 0.05). In apple juice, orange juice and MEB, z-values of A. acidoterrestris for pH 3.5 and pH 4.0 were 12.2 ± 1.3–14.2 ± 3.2 °C, 11.2 ± 0.3–9.4 ± 0.0 °C and 11.9 ± 0.8–10.3 ± 0.4 °C, respectively. z-values of apple juice, orange juice and MEB samples with SS = 10°Brix and SS = 20°Brix were 14.1 ± 3.2–12.2 ± 1.3 °C, 10.2 ± 0.7–10.5 ± 1.1 °C and 11.3 ± 1.5–10.9 ± 0.2 °C, respectively. However, D-values of all samples were affected by temperature significantly ( P < 0.01). Average D-values of apple juice, orange juice and MEB were 101.2 ± 14.7, 34.4 ± 7.9, 20.3 ± 4.9 and 4.3 ± 1.3 min for 85, 90, 95 and 100 °C. This study demonstrated that A. acidoterrestris spores exhibited high resistance to thermal processing applications. pH and SS of the media did not affect thermal resistance. [ABSTRACT FROM AUTHOR]