Hot air-assisted radio frequency heating for stabilization of rice bran: Enzyme activity, phenolic content, antioxidant activity and microstructure

Rice bran as a potent ingredient: unveiling its potential for value-added applications

Rice bran production significantly contributes to global environmental deterioration, yet its potential remains underutilized. This review discusses the nutritional composition, bioactive compounds, health benefits, limitations, and potential application of rice bran in both food and non-food sectors. While minor variations exist between pigmented and non-pigmented rice bran, the former is abundant in phytochemicals, which offer therapeutic benefits. The primary limitations hindering rice bran's food application include rancidity, toxic heavy metals, and antinutrients. Effective stabilization is crucial to extend rice bran's shelf life. Despite these challenges, rice bran holds significant potential for value-added products. Hence, its rich composition and diverse applications underscore its importance as a valuable resource for sustainable production practices.

Radiofrequency affects the decrystallization efficiency and physicochemical properties of rape honey via crystal structure modification and inactivating enzyme

Crystallization degrades the physicochemical properties of honey and reduces consumer acceptance. To address this issue, radiofrequency was developed to investigate the decrystallization efficiency and quality impact mechanism of rape honey. The results showed that radiofrequency significantly decreased the number and size of crystals, leading to shortening the decrystallization time to less than 10 min. The response surface optimization methodology further indicated that the highest decrystallization rate (98.72 ± 0.34 %) and lower 5-Hydroxymethylfurfural (2.45 ± 0.12 mg/kg) contents were obtained. Furthermore, radiofrequency changed the honey from a pseudoplastic into a Newtonian fluid efficiently due to the volumetric heating feature. It is worth noting that the inactivation of glucose oxidase reduced the antibacterial capacity, while the increase in total phenolic and flavonoid contents improved the antioxidant capacity of rape honey. In summary, current findings indicated that radiofrequency is a potential alternative decrystallization technology for water baths.

Combined treatment of rice bran by solid-state fermentation and extrusion: Effect of processing sequence and microbial strains

Solid-state fermentation (SSF) and extrusion are effective methods to improve the nutritional and sensory quality of rice bran. The effect of the processing sequence of SSF and extrusion and microbial strains on the quality of rice bran was studied. The results showed that the first SSF followed by extrusion increased the contents of phenolic, flavonoid and γ-oryzanol, but the color changed to brown. The first extrusion followed by SSF caused damage to bioactive components and antioxidant activity, but significantly increased the content of arabinoxylans. The difference between the two processing sequences may be related to the process time and the effect of substrate on microbial induction. Aspergillus oryzae and Neurospora sitophila were suitable for increasing the bioactive components of rice bran, while Lactiplantibacillus plantarum was suitable for increasing water-extractable arabinoxylan content. Different processing sequences and microbial strains have their advantages, and these results can provide reference for rice bran processing.

Influences of emerging drying technologies on rice quality

Rice is an important staple food in the world. Drying is an important step in the post-harvest handling of rice and can influence rice qualities and thus play a key role in determining rice commercial and nutritional value. In rice processing, traditional drying methods may lead to longer drying times, greater energy consumption, and unintended quality losses. Thus, it is imperative to improve the physical, chemical, and milling properties of rice while preserving its nutritional value, flavor, and appearance as much as possible. Additionally, it is necessary to increase the efficiency with which heat energy is utilized during the thermal processing of freshly harvested paddy. Moreover, this review provides insights into the current application status of six different innovative drying technologies such as radio frequency (RF) drying, microwave (MW) drying, infrared (IR) drying, vacuum drying (VD), superheated steam (SHS) drying, fluidized bed (FB) drying along with their effect on the quality of rice such as color, flavor, crack ratio, microstructure and morphology, bioactive components and antioxidant activity as well asstarch content and glycemic index. Dielectric methods of drying due to volumetric heating results in enhanced drying rate, improved heating uniformity, reduced crack ratio, increased head rice yield and better maintain taste value of paddy grains. These novel emerging drying techniques increased the interactions between hydrated proteins and swollen starch granules, resulting in enhanced viscosity of rice flour and promoted starch gelatinization and enhanced antioxidant activity which is helpful to produce functional rice. Moreover, this review not only highlights the existing challenges posed by these innovative thermal technologies but also presents potential solutions. Additionally, the combination of these technologies to optimize operating conditions can further boost their effectiveness in enhancing the drying process. Nevertheless, future studies are essential to gain a deeper understanding of the mechanism of quality changes induced by emerging processing technologies. This knowledge will help expand the application of these techniques in the rice processing industry.

Developing Lipase Inhibitor as a Novel Approach to Address the Rice Bran Rancidity Issue─A Critical Review

Rice bran is a valuable byproduct from the food processing industry, which contains abundant protein, essential unsaturated fatty acids, and numerous bioactive compounds. However, its susceptibility to rancidity greatly restricts its wide utilization. Many strategies have been proposed to delay the rancidity of rice bran, but most of them have their respective limitations. Here, we proposed that developing rice ban lipase peptide inhibitors represents an alternative and promising prescription for impeding the rancidity of rice bran, in contrast to the conventional stabilization approaches for rice bran. For this reason, the rancidity mechanisms of rice bran and the research progress of rice bran lipases were discussed. In addition, the feasibility of utilizing in silico screening and phage display, two state-of-the-art technologies, in the design of the related peptide inhibitors was also highlighted. This knowledge is expected to provide a theoretical basis for opening a new avenue for stabilizing rice bran.

Impact of thermal processing on dietary flavonoids

Flavonoids are a class of polyphenols which are widely distributed in natural products and foods. They have diverse bioactivities, including anti-inflammatory, anti-aging, and antioxidant activities. Generally, the foods rich in flavonoids are usually consumed after thermal processing. However, thermal stability of flavonoids is usually low, and thermal processing could cause either positive or negative influences on their stability and bioactivities. In this review, the effects of thermal processing on thermal stability and bioactivity of dietary flavonoids from different food sources are summarized. Then, strategies to improve thermal stability of dietary flavonoids are discussed and the effect of some promising thermal technologies are also preliminary clarified. The promising thermal technologies may be alternative to conventional thermal processing technologies.

Effects of corn drying and storage conditions on flour, starch, feed, and ethanol production: a review

The objective was to review the effects of the drying and storage conditions of corn on the physical-chemical quality in the processing of starch and flour, in the production of animal feed, and in the industrialization of ethanol. Initially, the review presented an overview of the post-harvest stages of corn grains, highlighting drying and storage. The main drying and storage methods used for corn grains were presented. Among the drying conditions, the air temperature was the main factor that affected the properties of starch, flour, feed, and ethanol produced from corn. It was verified that the corn grains submitted to drying at temperatures below 60 °C obtained better results in the industry. In storage, in addition to the storage time, factors such as temperature and moisture content of the grains affected the physical-chemical quality of the processed products. In this stage, the moisture content below 14% and the storage temperature below 25 °C conserved the physical-chemical quality of the grains and obtained better processing results. Further studies are needed to assess the effects of the drying and storage conditions of corn on the properties of flour, starch, animal feed, and, mainly, ethanol production.

Graphical abstract

Rice Bran: From Waste to Nutritious Food Ingredients

Rice (Oryza sativa L.) is a principal food for more than half of the world's people. Rice is predominantly consumed as white rice, a refined grain that is produced during the rice milling process which removes the bran and germ and leaves the starchy endosperm. Rice bran is a by-product produced from the rice milling process, which contains many bioactive compounds, for instance, phenolic compounds, tocotrienols, tocopherols, and γ-oryzanol. These bioactive compounds are thought to protect against cancer, vascular disease, and type 2 diabetes. Extraction of rice bran oil also generates various by-products including rice bran wax, defatted rice bran, filtered cake, and rice acid oil, and some of them exert bioactive substances that could be utilized as functional food ingredients. However, rice bran is often utilized as animal feed or discarded as waste. Therefore, this review aimed to discuss the role of rice bran in metabolic ailments. The bioactive constituents and food product application of rice bran were also highlighted in this study. Collectively, a better understanding of the underlying molecular mechanism and the role of these bioactive compounds exerted in the rice bran would provide a useful approach for the food industry and prevent metabolic ailments.

Stabilization of Rice Bran: A Review

One of the major problems in food science is meeting the demand of the world's growing population, despite environmental limitations such as climate change, water scarcity, land degradation, marine pollution, and desertification. Preventing food from going to waste and utilizing nutritive by-products as food rather than feed are easy and powerful strategies for overcoming this problem. Rice is an important staple food crop for more than half of the world's population and substantial quantities of rice bran emerge as the main by-product of rice grain milling. Usually, rice bran is used as animal feed or discarded as waste. Although it is highly nutritious and comprises many bioactive compounds with considerable health benefits, the rapid deterioration of bran limits the exploitation of the full potential of rice bran. Hydrolytic rancidity is the main obstacle to using rice bran as food, and the enzyme inactivation process, which is termed stabilization, is the only way to prevent it. This study reviews the methods of stabilizing rice bran and other rice-milling by-products comprising rice bran in the context of the efficiency of the process upon storage. The effect of the process on the components of rice bran is also discussed.

Hot-air-assisted radio frequency blanching of broccoli: heating uniformity, physicochemical parameters, bioactive compounds, and microstructure

BACKGROUND

Vegetables are often blanched before drying. The hot-water blanching (HWB) of broccoli reduces quality and is environmentally harmful. In this work, hot-air-assisted radio frequency heating blanching (HA-RFB) of broccoli was developed for use before further drying processes. Blanching sufficiency, heating uniformity, and heating rate during HA-RFB were investigated to improve the product's physicochemical properties and texture. Suitable heating conditions were achieved when HA-RFB was applied with hot air at 70 °C, with an electrode gap of 10.7 cm, using a cylindrical container for the broccoli.

RESULTS

Under these conditions, the relative peroxidase activity in broccoli decreased to 3.26% within 117 s, with 13.45% of weight loss. In comparison with HWB broccoli, the products blanched by HA-RFB preserved their texture, bioactive compounds, and microstructure better. The ascorbic acid, sulforaphane, and total glucosinolate content in HA-RFB products were 251.1%, 131.9% and 36.7% higher than those in HWB broccoli, and HA-RFB treatment led to a greater weight loss (13.45 ± 0.50%) than HWB (8.70 ± 1.70%), which is very helpful for the subsequent drying process.

CONCLUSION

This study demonstrated that HA-RFB could be a promising substitute for HWB to blanch broccoli and other flower vegetables, especially as a pretreatment in the drying process. © 2023 Society of Chemical Industry.

Rice Bran and Its Potential To Complement the Nutritional Needs of Children and Elderly

Rice bran is an agro-industrial by-product of low added value that can be used to complement human nutritional needs. In this work, the profile of minerals, fatty acids and amino acids in brown rice bran was determined, aiming to evaluate its potential to complement the nutritional needs of different age groups, according to recommendations of regulatory agencies. The brown rice bran was supplied by a rice processing industry located in the south of the state of Rio Grande do Sul. Minerals were quantified using an emission spectrometer; the fatty acid profile was determined by gas chromatography and the amino acids were quantified by high-performance liquid chromatography with fluorescence (HPLC-FL). The main minerals were phosphorus (P), magnesium (Mg), potassium (K) and calcium (Ca) (2,933, 1,029, 211 and 56 mg / 100 g of rice bran). Saturated, monounsaturated and polyunsaturated fatty acids in rice bran were 22.4, 36.2 and 34.5% of lipid content, respectively. The polar, neutral and charged amino acids represented 8.8, 9.3 and 12.8% of the protein content, respectively. The composition of this co-product of rice supply chain is a good alternative to the new demand on plant-based food supplying the recommended daily intake (RDI) of national and international food polices.

Recent developments in radio frequency drying for food and agricultural products using a multi-stage strategy: a review

Radio frequency (RF) drying is an emerging technology for food and agricultural products, holding features of rapid, uniform, stable, and volumetric heating, high energy efficiency, and moisture leveling. However, the RF drying with a single stage commonly has drawbacks of unexpected product quality, non-uniform moisture distribution, and prolonged drying time. The multi-stage drying approach could overcome the shortcomings of one-stage strategy accordingly by applying different drying methods or operating parameter values in each phase separately. This review describes the principle of RF heating, presents the typical systems and superiorities of RF drying, and provides a comprehensive overview on recent development in applications of both the one-stage and the multi-stage RF drying, and analysis of drying characteristics and merits for different types of the two-stage strategy. This review finally proposes recommendations for future studies in improving and optimizing the existing RF drying protocols and scaling up them to industrial applications.

Effects of Radio Frequency Heating on the Stability and Antioxidant Properties of Rice Bran

Radio frequency (RF) technology is considered as a rapid heating method. Lipase in rice bran could highly accelerate lipid oxidation. The objectives of this study were to establish the radio frequency heating conditions for lipase inactivation and to evaluate the stability and antioxidant capacity. The results showed that the suitable electrode gap for a 1 kg sample load was 6 cm, and it only took 2 min to heat rice bran from 25 °C to 100 °C. Besides, there were no significant differences in the total phenolic content, flavonoid content and color between the untreated and RF-treated group, and the DPPH free radical scavenging activity of the RF treatment reached 84.8%. The acid value, free fatty acid content and peroxide value of the RF-treated rice bran met the quality standard after 8 weeks of storage at 4, 25 and 37 °C. In summary, this study provides valuable information about the RF heating procedure, and shows the great potential of RF technology for stabilizing rice bran efficiently.