Pressure-assisted thermal processing (PATP) is an emerging sterilization technology in which a combination of pressure (500 to 700 MPa) and temperature (90 to 120 degrees C) are used to inactivate bacterial spores. The objective of this study was to examine the role of pressurization rate and pressure pulsing in enhancing PATP lethality to the bacterial spore. Bacillus amyloliquefaciens TMW 2.479 spore suspensions were prepared in deionized water at three inoculum levels (1.1 x 10(9), 1.4 x 10(8), and 1.3 x 10(6) CFU/ml), treated at two pressurization rates (18.06 and 3.75 MPa/s), and held at 600 MPa and 105 degrees C for 0, 0.5, 1, 2, 3, and 5 min. Experiments were carried out using custom-fabricated, high-pressure microbial kinetic testing equipment. Single and double pulses with equivalent pressure-holding times (1 to 3 min) were investigated by using the spore suspension containing 1.4 x 10(8) CFU/ml. Spore survivors were enumerated by pour plating, using Trypticase soy agar after incubation at 32 degrees C for 2 days. During short pressure-holding times (< or = 2 min), PATP treatment with the slow pressurization rate provided enhanced spore reduction over that of the fast pressurization rate. However, these differences diminished with extended pressure-holding times. After a 5-min pressure-holding time, B. amyloliquefaciens population decreased about 6 log CFU/ml, regardless of pressurization rate and inoculum level. Double-pulse treatment enhanced PATP spore lethality by approximately 2.4 to 4 log CFU/ml, in comparison to single pulse for a given pressure-holding time. In conclusion, pressure pulsing considerably increases the efficacy of PATP treatment against bacterial spores. Contribution of pressurization rate to PATP spore lethality varies with duration of pressure holding.

Summary Jasmine rice (Oryza sativa L.) was subjected to two drying operations: combined microwave‐hot air drying (MHA) at initial power intensity of 3, 4 and 6 W g−1 and superheated steam drying (SHS) at 300 °C and 400 °C. During drying, kinetic rate constants of SHS were significantly higher than those of MHA. Both drying operations could decrease enthalpy of starch gelatinisation from 9.28 J g−1 to 1.64–6.17 J g−1, increase gelatinisation extent to 33.51–82.33%, decrease crystallinity from 28.87% to 18.15–21.33%, improve scavenging ability of 1,1‐diphenyl‐2‐picrylhydrazyl, increase ferric reducing antioxidant power and increase hardness of cooked rice from 5.66 N to 5.83–6.55 N, depending on microwave power and drying medium temperature. However, taste profiles and liking scores were comparable to the regular brown rice. Therefore, MHA and SHS operations could be potentially used for reducing drying process and promoting antioxidant activity.

Effect of organic acids (acetic, citric, and lactic; 100 mM, pH 5) on spore inactivation by pressure-assisted thermal processing (PATP; 700 MPa and 105 degrees C), high pressure processing (HPP; 700 MPa, 35 degrees C), and thermal processing (TP; 105 degrees C, 0.1 MPa) was investigated. Bacillus amyloliquefaciens spores were inoculated into sterile organic acid solutions to obtain a final concentration of approximately 1.3 x 10(8) CFU/mL. B. amyloliquefaciens spores were inactivated to undetectable levels with or without organic acids after 3 min PATP holding time. At a shorter PATP treatment time (approximately 2 min), the inactivation was greater when spores were suspended in citric and acetic acids than in lactic acid or deionized water. Presence of organic acids during PATP resulted in 33% to 80% germination in the population of spores that survived the treatment. In contrast to PATP, neither HPP nor TP, for up to 5 min holding time with or without addition of organic acids, was sporicidal. In a separate set of experiments, carrot puree was tested, as a low-acid food matrix, to study spore recovery during extended storage following PATP. Results showed that organic acids were effective in inhibiting spore recovery in treated carrot puree during extended storage (up to 28 d) at 32 degrees C. In conclusion, addition of some organic acids provided significant lethality enhancement (P < 0.05) during PATP treatments and suppressed spore recovery in the treated carrot puree.

Consumption of glutinous rice has been increasing. Leum Pua rice (Oryza sativa Linn.) is black glutinous rice containing high nutrition, but its cooking process is time-consuming. This study aimed at decreasing cooking time by changing rice properties using superheated steam treatment. The black glutinous rice was subjected to pretreatment: uncooking and precooking before superheated steam treatment at 250°C and 300°C. Drying rate constant (k) of uncooked rice was 0.0301–0.0744 s−1. Precooking rice prior to superheated steam treatment at 300°C reduced the kinetic rate constant to 0.0596 s−1. From SEM, porosity of the treated rice was observed. However, superheated steam treatment reduced ferric reducing antioxidant power and total phenolic content, compared with control. From X-ray diffraction, A-type crystalline structure of the treated rice was disappeared. Cooking time of the superheated steam-treated rice was reduced to 1–5 min. Their hardness and overall liking scores were comparable to control.

Brown rice (Oryza sativa L.) was subjected to ultrasonic treatment (UT) and three enzymatic treatments (ET) with cellulase, glucoamylase and α‐amylase. All treatments changed pasting properties of brown rice flour and structure of brown rice grain surface, but only UT and α‐amylase treatment (AT) significantly affected starch granules inside the grain. During cooking, water uptake and volume expansion of UT brown rice were higher than those of ET. Both UT and ET decreased hardness of the cooked brown rice from 206.05 N to 192.22–154.02 N in which the AT cooked rice was the softest. Although UT reduced hardness and increased volume expansion, the brown rice from AT had the highest liking score. Principle component analysis also visualized the preferable brown rice from AT. Therefore, AT was considered to potentially become a novel technology for development of high‐quality brown rice. Practical applications Brown rice is normally soaked in water before cooking. Modifying the structure of brown rice by ultrasonic or enzymatic treatment could improve water uptake, volume expansion and texture of the cooked brown rice. Therefore, enzymatic treatment by α‐amylase was recommended to produce the soften brown rice without soaking before cooking.

Microwaves have been applied for cooking, warming, and thawing food for many years. Microwave heating differs from conventional heating and may cause variation in the food quality. This study determined the quality of Riceberry rice (Oryza sativa L.) after microwave cooking using various rice-to-water ratios at three power levels (360, 600, and 900 W). The texture of all microwave-cooked samples was in the range 162.35 ± 5.86 to 180.11 ± 7.17 N and was comparable to the conventionally cooked rice (162.03 N). The total phenolic content (TPC) and the antioxidant activity of the microwave-cooked rice were higher than those of the conventional-cooked rice. Microwave cooking appeared to keep the TPC in the range 241.15–246.89 mg GAE/100 g db and the antioxidant activities based on DPPH and ABTS assays in the ranges 134.24–137.15 and 302.80–311.85 mg·TE/100 g db, respectively. Microwave cooking also maintained similar contents of fiber, ash, and total starch to those from conventional cooking. The glycemic index (GI) for all freshly cooked rice samples was not significantly different, and the rice was classified as a high-GI food. Microwave cooking could be recommended as an alternative technique for rice cooking due to its rapid heating regime and the comparable quality and maximized TPC and antioxidant activity of the cooked rice.

Brown rice (Oryza sativa Linn.) was subjected to ultrasonic treatment (UT) and enzymatic treatment (ET) with cellulase (CT), glucoamylase (GT), and α‐amylase (AT). UT showed no significant effect on thermal properties, crystalline pattern and, glycemic response of brown rice. AT decreased gelatinization enthalpy from 7.19 g/J (control) to 5.31 g/J and reduced degree of crystallinity from 23.06% (control) to 21.02%. These changes significantly increased glycemic index of AT brown rice. CT and GT had insignificant effect on crystallinity and thermal properties of rice. Both UT and ET decreased hardness of cooked rice from 206.05 to 189.63–148.87 N in which the AT cooked rice was the softest. Both AT and UT were potentially used as novel processes to develop the soften brown rice. However, UT brown rice had lower glycemic response, required shorter cooking time, and was more practically produced in industrial scale than ET brown rice. Practical applications Soaking is the hydration process, which is normally used for brown rice before cooking. However, it is inconvenient and time‐consuming. Results of this study revealed the effects of enzymatic and ultrasonic treatments (UTs) on modifying of the bran layer and changing of physiochemical properties of rice grains. These changes promoted water uptake, reduced hardness, and improved cooking properties of brown rice. In consideration of glycemic response, UT represents good practice in the production of soften brown rice without soaking before cooking.

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