Enzymatic polishing of rice – A new processing technology

A Rapid and Accurate Quantitative Analysis of Cellulose in the Rice Bran Layer Based on Near-Infrared Spectroscopy

Cultivating rice varieties with lower cellulose content in the bran layer has the potential to enhance both the nutritional value and texture of brown rice. This study aims to establish a rapid and accurate method to quantify cellulose content in the bran layer utilizing near-infrared spectroscopy (NIRS), thereby providing a technical foundation for the selection, screening, and breeding of rice germplasm cultivars characterized by a low cellulose content in the bran layer. To ensure the accuracy of the NIR spectroscopic analysis, the potassium dichromate oxidation (PDO) method was improved and then used as a reference method. Using 141 samples of rice bran layer (rice bran without germ), near-infrared diffuse reflectance (NIRdr) spectra, near-infrared diffuse transmittance (NIRdt) spectra, and fusion spectra of NIRdr and NIRdt were used to establish cellulose quantitative analysis models, followed by a comparative evaluation of these models' predictive performance. Results indicate that the optimized PDO method demonstrates superior precision compared to the original PDO method. Upon examining the established models, their predictive capabilities were ranked in the following order: the fusion model outperforms the NIRdt model, which in turn surpasses the NIRdr model. Of all the fusion models developed, the model exhibiting the highest predictive accuracy utilized fusion spectra (NIRdr-NIRdt (1st der)) derived from preprocessed (first derivative) diffuse reflectance and transmittance spectra. This model achieved an external predictive R2p of 0.903 and an RMSEP of 0.213%. Using this specific model, the rice mutant O2 was successfully identified, which displayed a cellulose content in the bran layer of 3.28%, representing a 0.86% decrease compared to the wild type (W7). The utilization of NIRS enables quantitative analysis of the cellulose content within the rice bran layer, thereby providing essential technical support for the selection of rice varieties characterized by lower cellulose content in the bran layer.

Pre-gelatinization and cellulase addition improve fermentation performance and antioxidant activity of black rice wine

BACKGROUND

Black rice contains a variety of bioactive substances that contribute to the high nutritional value of black rice wine (BRW). However, the dense bran layer of black rice retards the fermentation rate and reduces the dissolution of active components. Hence, this study aims to investigate the effects of pre-gelatinization (PG) before cooking and cellulase (CE) addition during fermentation on the fermentation performance of BRW and its antioxidant activity.

RESULTS

PG combined with CE treatments (PGCE) increases the alcohol content, free amino acid content, volatile flavor content and total antioxidant activity of BRW by 90.81%, 15.36%, 38.05% and 19.56%, respectively, compared with the control group. Scanning electron microscopy, low-field nuclear magnetic resonance and texture properties analysis indicate that PG treatment increases gelatinization degree of starch during cooking, decreases bound water content in cooked black rice and promotes unbound water release. CE destroys the aleurone layer structure, facilitates the release of unbound water and the exposure of rice starch, thus increasing the reaction area and extravasation content significantly, which is beneficial to microbial growth and fermentation. Incomplete aleurone layer also promotes the dissolution of anthocyanins, phenols and other active substances, increasing the antioxidant activities of BRW.

CONCLUSION

PG and CE treatments reduce the fermentation time and improve the quality of BRW by destroying the black rice structure. © 2022 Society of Chemical Industry.

Drying Characteristics and Quality Attributes Affected by a Fluidized-Bed Drying Assisted with Swirling Compressed-Air for Preparing Instant Red Jasmine Rice

A new process for the production of instant red jasmine rice was investigated using fluidized bed drying with the aid of swirling compressed air. Drying characteristics were evaluated using the operating parameters of fluidizing air temperature (90–120 °C) and pressure of swirling compressed air (4–6 bar). Appropriate air pressure was determined based on the highest value of model parameters from the semi-empirical Page equation and effective diffusivity. Influences of supply time of swirling compressed air (2–10 min) and drying temperature of 90–120 °C were investigated and optimized based on the quality attributes using response surface methodology. Drying at 120 °C and compressed air pressure of 6 bar gave the highest rate constant and effective diffusion coefficient. Drying at 120 °C combined with injecting swirling air for 2 min was the most suitable approach, while drying at 90 °C and supplying compressed air for 10 min was the best choice to preserve antioxidant properties. Air temperature of 98.5 °C with 2 min supply of swirling compressed air suitably provided high physical and rehydration properties and retained high health benefits of antioxidant compounds. Finally, after rehydration in warm water at 70 °C for 10 min, the textural properties of the rehydrated rice sample were comparable to conventionally cooked rice.

Influence of microwave heating as accelerated aging on physicochemical, texture, pasting properties, and microstructure in brown rice of selected Indian rice varieties

Most of the population does not prefer to consume brown rice because of its strong nutty and chewy texture imparted by bran and germ. The present study has been undertaken to investigate the influence of accelerated aging through microwave (MW) heating at a lower and higher MW power levels of 950 and 1,400 W for 72 and 91 s to observe the changes in physicochemical, texture, pasting properties, sensory attributes, and microstructure of selected rice varieties (Sona masuri and RNR-15048) stored as brown rice for 6 months. The results revealed a significant decrease in moisture, amylose, free fatty acids (FFAs) with changes in color (L*, a*, and b* values) in both the varieties treated at 1,400 W for 91 s. An increase in kernel elongation ratio, water uptake, and a decrease in cooking time and solid loss was noted in both the varieties. After cooking, the texture of both the varieties showed an increase in hardness with reduced stickiness at both lower and higher MW power levels of 950 W for 72 s and 1,400 W for 91 s compared to untreated brown rice with an improved porous structure when observed under SEM analyzer followed by better water absorption and organoleptic properties after cooking. The reduction in final viscosity has been noted in both the varieties at 1,400 W for 91 s due to the binding of FFA with starch. Thus, the MW power level of 950 W for 72 s and 1,400 W for 91 s showed the better results for short-grain varieties like Sona masuri and RNR-15048 stored as brown rice.

Effect of enzyme pretreatment on dehulling, cooking time and protein content of pigeon pea (variety BDN2)

This study was carried out to investigate the effect of enzymatic pretreatment at different enzyme concentration, incubation time, incubation temperature and tempering water pH on the hulling efficiency, cooking quality and protein content of pigeon pea (variety BDN2). Response surface methodology based on a four-factor, five-level, central composite design was employed to study the effect of the independent variables and optimize processing conditions. A quadratic model satisfactorily described the hulling efficiency, cooking time and protein content with high value for the coefficient of determination R² (0.95, 0.92 and 0.97 respectively). It predicted a maximum hulling efficiency of 84.35%, minimum cooking time 13.06 min and maximum protein content 22.60% at enzyme concentration, and 31.34 mg/100 g dry matter, incubation time, 8.72 h, incubation temperature, 43.47 °C and tempering water, pH 5.99. Results were also compared with hulling efficiency, cooking time and protein content obtained with traditional oil pretreated method 78.30%, 14.30 min and 18.53% respectively. It revealed that hulling efficiency and protein content of enzyme pretreated pigeon pea could be increased 2.44% and 6.77% respectively, whereas cooking time could be reduced 1.50 min compared to the oil pretreated method.

Textural Properties, Resistant Starch, and in Vitro Starch Digestibility as Affected by Parboiling of Brown Glutinous Rice in a Retort Pouch

The effects that two preparation methods (parboiling with different degrees of gelatinization and parboiling with enzymatic hydrolysis) have on the qualities of brown glutinous rice were investigated in order to optimize the pretreatment conditions of brown glutinous rice for the ready-to-eat product in retort pouch. The brown glutinous rice was parboiled at various temperatures (50, 70 and 90C) and steamed at atmospheric pressure until the gelatinize level of 60, 80 and 100%. For the parboiling with enzymatic hydrolysis, the brown glutinous rice was immersed in xylanase before steamed. Results showed that parboiling not only affected the nutritional composition, color, and texture of glutinous rice but also decreased the Glycemic index (GI) to 61.3 ± 0.03 and raised the Resistance starch (RS) to 2.9 ± 0.02. There was interaction among RS, GI, and the amylopectin content of brown glutinous rice during parboiling without enzymatic hydrolysis. Amylopectin is directly proportional to GI but inversely proportional to RS. Enzymatic hydrolysis improved both the texture and the physical and chemical properties. In addition, the GI value of enzyme treated samples decreased to 62.7 ± 0.24 and the RS increased to 2.9 ± 0.05. The highest overall preference score was attained by parboiled rice which was soaked in water at 90°C and then steamed until 100%gelatinization.

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.

Fungal Biomass Protein Production from Trichoderma harzianum Using Rice Polishing

Industrially important enzymes and microbial biomass proteins have been produced from fungi for more than 50 years. High levels of crude protein as much as 45% are present in fungal biomass with balanced essential amino acids. The aim of this study was to access the potential of Trichoderma harzianum to produce fungal biomass protein from rice polishings. Maximum biomass yield was obtained at 5% (w/v) rice polishings after 72 h of incubation at 28°C at pH 4. Carbon and nitrogen ratio of 20 : 1 gave significantly higher production of fungal biomass protein. The FBP in the 75 L fermenter contained 49.50% crude protein, 32.00% true protein, 19.45% crude fiber, 9.62% ash, 11.5% cellulose content, and 0.325% RNA content. The profile of amino acids of final FBP exhibited that all essential amino acids were present in great quantities. The FBP produced by this fungus has been shown to be of good nutritional value for supplementation to poultry. The results presented in this study have practical implications in that the fungus T. harzianum could be used successfully to produce fungal biomass protein using rice polishings.

Enzymatic processing of pigmented and non pigmented rice bran on changes in oryzanol, polyphenols and antioxidant activity

Bran from different rice varieties is a treasure of nutrients and nutraceuticals, and its use is limited due to the poor sensory and functional properties. Application of enzymes can alter the functional and phytochemical properties. So the effect of endo-xylanase, cellulase and their combination on microstructural, nutraceutical and antioxidant properties of pigmented (Jyothi) and non-pigmented (IR64) rice bran were investigated. Scanning electron micrograph revealed micro structural changes in fibre structures on processing. All the enzymatic processing methods resulted in an increase in the content of oryzanol, soluble, bound and total polyphenols, flavonoid and tannin. It also showed an increase in the bioactivity with respect to free radical scavenging activity and total antioxidant activity. However, extent of the increase in bio-actives varied with the type of bran and enzyme application method. Endo-xylanase showed higher percentage difference compared to controls of Jyothi and IR64 bran extracts respectively in the content of the bound (10 & 19 %) and total (20 & 14 %) polyphenols. Combination of both the enzymes resulted in higher percentage increase of bioactive components and properties. It resulted in greater percentage difference compared to controls of Jyothi and IR64 extracts respectively in the content of soluble (58 & 17 %) and total (21 & 14 %) polyphenols, flavonoids (12 & 38 %), γ-oryzanol (10 & 12 %), free radical scavenging activity (64 & 30 %) and total antioxidant activity (82 & 136 %). It may be concluded that enzymatic bio-processing of bran with cellulose and hemicellulose degrading enzymes can improve its nutraceutical properties, and it may be used for development of functional foods.

Enzymatic polishing of cereal grains for improved nutrient retainment

Consumer acceptance of food products is largely driven by the dietary and functional quality of their ingredients. Though whole cereal grains are well known for bioactive components, scientists are facing dire need for better technologies to prevent the nutritional losses incurred through the conventional food processing technologies. Application of enzyme for depolymerisation of carbohydrates present in bran layer of grain is becoming an efficient method for phenolic mobilization and dietary fiber solubilisation. The present article emphasizes deep insights about the application of enzyme as an alternative technology for cereal grain processing to improve the product quality while forbidding the nutritional losses in an eco-friendly manner.

Optimization of Xylanase production from Penicillium sp.WX-Z1 by a two-step statistical strategy: Plackett-Burman and Box-Behnken experimental design

The objective of the study was to optimize the nutrition sources in a culture medium for the production of xylanase from Penicillium sp.WX-Z1 using Plackett-Burman design and Box-Behnken design. The Plackett-Burman multifactorial design was first employed to screen the important nutrient sources in the medium for xylanase production by Penicillium sp.WX-Z1 and subsequent use of the response surface methodology (RSM) was further optimized for xylanase production by Box-Behnken design. The important nutrient sources in the culture medium, identified by the initial screening method of Placket-Burman, were wheat bran, yeast extract, NaNO(3), MgSO(4), and CaCl(2). The optimal amounts (in g/L) for maximum production of xylanase were: wheat bran, 32.8; yeast extract, 1.02; NaNO(3), 12.71; MgSO(4), 0.96; and CaCl(2), 1.04. Using this statistical experimental design, the xylanase production under optimal condition reached 46.50 U/mL and an increase in xylanase activity of 1.34-fold was obtained compared with the original medium for fermentation carried out in a 30-L bioreactor.

Functional properties of protein isolates extracted from stabilized rice bran by microwave, dry heat, and parboiling

Protein isolates extracted from differently stabilized rice bran were analyzed to work out the food use potential. Bulk density remained higher for isolates obtained from heat stabilized bran, the treatments were found to have positive impact on the oil absorption properties, while the water absorption was slightly impaired owing to some possible configurational changes. Surface hydrophobicity and emulsion properties were improved with bran stabilization. Isolates exhibited better foaming properties owing to the flexible nature of protein molecules, with less intensive disulfide bonding, that were slightly affected by the stabilization treatment. Nitrogen solubility index followed a curved pattern with the least value near isoelectric point that showed an increasing trend toward basic pH, and parboiled protein isolates exhibited better gelling properties among the isolates.