Effects of Superheated Steam Fluidized Bed Drying on the Quality of Parboiled Germinated Brown Rice

A Comprehensive Study on the Influence of Superheated Steam Treatment on Lipolytic Enzymes, Physicochemical Characteristics, and Volatile Composition of Lightly Milled Rice

Enzyme inactivation is crucial for enhancing the shelf life of lightly milled rice (LMR), yet the impact of diverse superheated steam (SS) treatment conditions on lipolytic enzyme efficiency, physicochemical properties, and volatile profiles of LMR remains unclear. This study investigated varying SS conditions, employing temperatures of 120 °C, 140 °C, and 160 °C and exposure times of 2, 4, 6, and 8 min. The research aimed to discern the influence of these conditions on enzyme activities, physicochemical characteristics, and quality attributes of LMR. Results indicated a significant rise in the inactivation rate with increased treatment temperature or duration, achieving a notable 70% reduction in enzyme activities at 120 °C for 6 min. Prolonged exposure to higher temperatures also induced pronounced fissures on LMR surfaces. Furthermore, intensive SS treatment led to a noteworthy 5.52% reduction in the relative crystallinity of LMR starch. GC/MS analysis revealed a consequential decrease, ranging from 44.7% to 65.7%, in undesirable odor ketones post-SS treatment. These findings underscore the potential of SS treatment in enhancing the commercial attributes of LMR.

Superheated steam processing of cereals and cereal products: A review

The concept of superheated steam (SS) was proposed over a century ago and has been widely studied as a drying method. SS processing of cereals and cereal products has been extensively studied in recent years for its advantages of higher drying rates above the inversion temperature, oxygen-free environment, energy conservation, and environmental protection. This review provides a brief introduction to the history, principles, and classification of SS. The applications of SS processing in the drying, enzymatic inactivation, sterilization, mycotoxin degradation, roasting, and cooking of cereals and cereal products are summarized and discussed. Moreover, the effects of SS processing on the physicochemical properties of cereals and the qualities of cereal foods are reviewed and discussed. The applications of SS for cereal processing and its effects on cereal properties have been extensively studied; however, issues such as the browning of cereal foods, thermal damage of starch, protein denaturation, and nutrition loss have not been comprehensively studied. Therefore, further studies are required to better understand the mechanism of the quality changes caused by SS processing and to expand the fields of application of SS in the cereal processing industry. This review enhances the understanding of SS processing and presents theoretical suggestions for promoting SS processing to improve the safety and quality of cereals and cereal products.

Effects of a Combined Processes of Low-Pressure Steam Enrichment and Low-Pressure Superheated Steam Drying on the γ-Aminobutyric Acid Content of Japonica Rice

In order to improve the content of GABA in japonica rice, so as to improve the nutritional composition and enhance the added value of rice, this study explored a combined process of low-pressure steam enrichment of γ-aminobutyric acid (GABA) content in japonica rice and low-pressure superheated steam (LPSS) drying of japonica rice. The low-pressure energy and the energy stored in rice grains were used to promote water absorption and activation of rice germs in a steam environment. Under the action of glutamate decarboxylase, the germ glutamate underwent an enzymatic reaction to generate GABA, which was transferred to and stored in the rice endosperm due to the concentration gradient and water gradient. After germination, LPSS was successively applied to dry the rice grains. The response surface method was used to optimize the parameters of low-pressure wet steam enrichment and LPSS drying of the rice grains. The experimental results showed that when the pressure was 0.026 MPa, the temperature was 60.66°C, the time was 5.01 h, and the flow rate was 0.31 L/h; the GABA content produced by low-pressure wet steam germination of japonica rice peaked at 94.1751 mg/100 g. When the germinated and enriched japonica rice was put through LPSS drying with a pressure of 0.021 MPa, a temperature of 66.55°C, a time of 1.57 h, and a flow rate of 0.28 L/h, the GABA content peaked at 104.161 mg/100 g. The results show that the combined process of low-pressure steam enrichment and drying continuously produced GABA in the soaking enrichment and drying stages, and the content of GABA in the drying stage accounted for 10% of the total content, which effectively increased the content of GABA in japonica rice and shortened the enrichment time. This study provides a technical reference for industrialized production of GABA-rich brown rice, embryonic rice, and polished rice.

Superheated steam processing: An emerging technology to improve food quality and safety

Heat processing is one of the most efficient strategies used in food industry to improve quality and prolong shelf life. However, conventional processing methods such as microwave heating, burning charcoal treatment, boiling, and frying are energy-inefficient and often lead to inferior product quality. Superheated steam (SHS) is an innovative technology that offers many potential benefits to industry and is increasingly used in food industry. Compared to conventional processing methods, SHS holds higher heat transfer coefficients, which can reduce microorganisms on surface of foodstuffs efficiently. Additionally, SHS generates a low oxygen environment, which prevents lipid oxidation and harmful compounds generation. Furthermore, SHS can facilitate development of desired product quality, such as protein denaturation with functional characteristics, proper starch gelatinization, and can also reduce nutrient loss, and improve the physicochemical properties of foodstuffs. The current work provides a comprehensive review of the impact of SHS on the nutritional, physicochemical, and safety properties of various foodstuffs including meat, fruits, and vegetables, cereals, etc. Additionally, it also provides food manufacturers and researchers with basic knowledge and practical techniques for SHS processing of foodstuffs, which may improve the current scope of SHS and transfer current food systems to a healthy and sustainable one.

Application of Two-Stage Variable Temperature Drying in Hot Air-Drying of Paddy Rice

The aim of this study was to investigate the effect of two-stage variable temperature drying (VTD) on the quality and drying efficiency of paddy rice in the hot air-drying process. A constant temperature of 50 °C (CTD) was used as a control group. VTD and CTD methods were applied in a 15 ton batch type recirculating grain dryer. Three aspects (appearance quality, physical and chemical properties, taste quality) of the paddy rice samples from the dryer were measured and compared. It was observed that paddy rice with an initial moisture content of 25.3% (wet basis) was dried to 14% (wet basis). Compared to CTD, the VTD method could reduce the drying time and fissuring rate by 0.7 h and 42%, respectively. It had a head rice yield (HRY) of 78.45%, compared to 76.45% by CTD. The fatty acid content of the VTD samples was 2.28% lower than those of CTD, and it exhibited a 34% decrease in amylose content. These results show that two-stage VTD is an advanced hot air-drying method that can be used to improve the quality of dried paddy rice, maintain efficiency, and reduce the cost of the drying process by minimizing the rate of energy consumption.

Drying characteristics of ready-to-eat komal chawal rice: processing and modeling

A traditional ready-to-eat rice from Assam, India, known as komal chawal is produced by steaming of steeped chokuwa paddy, which is a low-amylose variety, and by drying the steamed paddy under shade as a measure of controlling the drying rate for sustenance of a quick rehydration quality. As an improvement over this traditional method in terms of production time, komal chawal is produced by parboiling the chokuwa brown rice with model predicted soaking and steaming conditions. Thin-layer drying behavior of the steamed brown rice was studied at drying temperatures of 40-60 °C, at an air velocity of 1 m/s. Among different thin-layer drying models, Page equation fitted best to the drying data, with the coefficient of determination (R2) and root mean square error as the measures for selection of the best fitted model. While the moisture diffusivity values were in the range of 2.08 × 10-10-3.34 × 10-10 m2/s, the effects of drying air temperature on the drying rate was modeled with an activation energy of 20.44 kJ/mol for an the Arrhenius kind of temperature dependence of diffusivity. Based on the effects of drying temperature on rehydration, textural, and pasting properties of the product a lower drying temperature is recommended.

Improvement of germinated brown rice quality with autoclaving treatment

Germinated brown rice (GBR) is a popular functional food containing considerable amounts of beneficial nutrients and bioactive compounds. Here, autoclaving at 115°C for 20 min was employed to process GBR (AGBR) to evaluate the effect of autoclaving on the nutritional and health function of GBR in microstructure, taste value, aroma, as well as the physiological ingredients. The results showed that autoclaving treatment influenced the starch gelatinization and aroma to improve the taste of cooked AGBR. Autoclaving treatment significantly increased the gamma‐aminobutyric acid (GABA) and ferulic acid levels of AGBR (p < .05). In addition, consuming AGBR for 1 month significantly decreased the fasting plasma glucose (FPG), 0.5, 1, and 2 hr postprandial plasma glucose (PPG), triglyceride (TG), total cholesterol (TC), high‐density lipoprotein cholesterol (HDL‐c), and low‐density lipoprotein cholesterol (LDL‐c) in metabolic syndrome (MS) patients (p < .05). Therefore, autoclaving treatment, as a promising processing strategy, may both improve the sensory attributes and the nutrition of GBR.

Superheated Steam Drying of Black Tea and Quality Improvement

The effects of drying temperature (120 °C to 200 °C) on drying characteristics of black tea leaves using superheated steam dryer (SHS) were investigated. It was observed that increased drying temperature caused higher drying rate that helped to shorten drying times. The effective diffusivities of moisture transfer in SHS ranged between 2.30 × 10–10 and 3.90 × 10–10 m2/s within the temperature range tested. The effective diffusivities were correlated by Arrhenius relationship with Arrhenius constant and activation energy estimated at 1.07 × 10–8 m2/s and activation energy 12.34 kJ/mol, respectively. Increased in drying temperature and time significantly decreased the brightness (*L) of tea leaves from 26.34 to 22.66 and TPC from 87.93 to 42.39 mg/g. However, comparison to commercial black tea showed that SHS dried-tea leaves exhibited better colour attribute and 91.4% higher in phenolic content.

Innovative processing techniques for altering the physicochemical properties of wholegrain brown rice (Oryza sativa L.) - opportunities for enhancing food quality and health attributes

Rice is a globally important staple consumed by billions of people, and recently there has been considerable interest in promoting the consumption of wholegrain brown rice (WBR) due to its obvious advantages over polished rice in metabolically protective activities. This work highlights the effects of innovative processing technologies on the quality and functional properties of WBR in comparison with traditional approaches; and it is aimed at establishing a quantitative and/or qualitative link between physicochemical changes and high-efficient processing methods. Compared with thermal treatments, applications of innovative nonthermal techniques, such as high hydrostatic pressure (HHP), pulsed electric fields (PEF), ultrasound and cold plasma, are not limited to modifying physicochemical properties of WBR grains, since improvements in nutritional and functional components as well as a reduction in anti-nutritional factors can also be achieved through inducing related biochemical transformation. Much information about processing methods and parameters which influence WBR quality changes has been obtained, but simultaneously achieving the product stabilization and functionality of processed WBR grains requires a comprehensive evaluation of all the quality changes induced by different processing procedures as well as quantitative insights into the relationship between the changes and processing variables.

Physicochemical properties of germinated dehulled rice flour and energy requirement in germination as affected by ultrasound treatment

Limited data are published regarding changes in the physicochemical properties of rice flours from germinated de-hulled rice treated by ultrasound. This work was undertaken to evaluate the effect of ultrasound treatment (25 kHz, 16 W/L, 5 min) on starch hydrolysis and functional properties of rice flours produced from ultrasound-treated red rice and brown rice germinated for up to 36 h. Environmental Scanning Electron Microscopy (ESEM) microimages showed that the ultrasound treatment altered the surface microstructure of rice, which helped to improve moisture transfer during steam-cooking. The flours from sonicated germinated de-hulled rice exhibited significantly (p < .05) enhanced starch hydrolysis, increased the glucose content, and decreased falling number values and viscosities determined by a Rapid Visco Analyzer. The amylase activity of the germinating red rice and brown rice displayed different sensitivity to ultrasonic treatment. The ultrasonic pre-treatment resulted in a significant reduction in energy use during germination with a potential to further reduce energy use in germinated rice cooking process. The present study indicated that ultrasound could be a low-power consumption method to modify the rheological behavior of germinated rice flour, as well as an efficient approach to improve the texture, flavor, and nutrient properties of steam-cooked germinated rice.

Numerical Simulation on Superheated Steam Fluidized Bed Drying at Different Operating Pressures

During superheated steam fluidized bed drying process, the operating pressure has an important influence on heat and mass transfer characteristics and the vapor-solid two-phase flow characteristics. Based on the two-dimensional unsteady model of rapeseeds drying process, the influence of operating pressure on the superheated steam fluidized bed drying kinetics was revealed by computer numerical simulation. The quantitative analysis of relationship between operating pressure and maximum drying rate was conducted under negative pressure, near atmospheric pressure and high pressure environment, respectively. The optimum operating pressure values for superheated steam fluidized bed drying were obtained with the imported superheated steam temperature and superficial velocity. The simulation results provide a theoretical reference for superheated steam fluidized bed drying technology applying to agro-processing projects.