Microwave Parboiling: Reduction in Process Time, Browning of Rice and Residual Phosphorus Content in the Waste Water.

The conventional prolonged parboiling process results in high operation cost and grain darkening, which may limit consumption. Moreover, residue generation by rice industries is another challenge. The objective of this study was to evaluate the use of microwave irradiation during soaking and gelatinization stages of parboiling rice. Processing time, colorimetric profile, broken and nongelatinized grains, sucrose and glucose content, free 5-hydroxymethyl-2-furfural, and residual phosphorus were evaluated. As the soaking and gelatinization times during microwave treatments increased, the colorimetric parameters increased; however, the values were lower than those with the conventional process. Regardless of soaking time, a decrease in broken and nongelatinized grains was obtained by using the lowest steaming time (5 min). Additionally, lower residual phosphorus content was found in soaking water (10 and 20 min) when using microwave irradiation. Under favorable conditions, a reduction in the levels of broken and nongelatinized grains, residual phosphorus, and color changes was observed, indicating that microwave irradiation may be more beneficial than conventional parboiling. PRACTICAL APPLICATION: Parboiling requires a high volume of water and soaking time, which leads to high costs, underutilization of infrastructures, and high residue in the water after processing. The rapid parboiling process involves the use of microwaves during the soaking and gelatinization stages. The main advantages of the microwave parboiling process include reduced processing time, ranging from 83% to 95%, higher gelatinization, greater yield, reduced darkening, and reduced residual phosphorus in the effluents by 60%. This report can aid industries in streamlining their processes, thereby providing a high-quality, lower cost, and environmentally safe product.

Discrimination of genotype and geographical origin of black rice grown in Brazil by LC-MS analysis of phenolics.

Physicochemical properties, cooking time, and phenolics profile of two black rice genotypes grown at six different locations in Brazil were determined. The cultivar IAC 600 and the elite-line AE 153045 were used. The main growing locations for black rice were considered, as follows: Alegrete (ALG), Capão do Leão (CPL), Guaratinguetá (GUA), Roseira (ROS), Santa Vitória do Palmar (SVP), and Taubaté (TBT). Principal component analysis (PCA) and supervised partial least squares-discriminant analysis (PLS-DA) from liquid chromatography-mass spectrometry (LC-MS) data sets showed distinction among genotypes and locations. Quercetin-3-O-glucoside and vanillic acid were the most relevant compounds for discriminating genotypes. SVP location provided the most distinctive black rice, with greater total phenolics content. Characteristics of black rice from SVP location were associated to effects of latitude and wind conditions. Hesperetin, vanillic acid, quercetion-3-O-glucoside, and p-coumaric acid were the most relevant compounds for discriminating locations.

Impact of cooking temperature on the quality of quick cooking brown rice.

Three cooking temperatures (72, 80, and 88 °C) were applied to two rice genotypes (Puitá Inta CL and INOV CL) for preparing quick cooking brown rice. Samples were analyzed for cooking time, color, scanning electron microscopy (SEM), damaged grains, amylose, protein content and extractability, differential scanning calorimetry (DSC), X-ray diffraction (XRD), sensory properties, and in vitro digestion. Cooking time was reduced from 23.0-23.6 to 5.5-6.9 min when the highest temperature was applied, depending on genotype. The greatest grain deformation was observed for treatments from Puitá Inta CL. XRD showed greater ability of brown rice from Puitá Inta CL to gelatinize at 88 °C. Appearance, texture, and flavor of quick cooking brown rice prepared at 88 °C was inferior to its brown rice counterparts. Starch digestibility decreased by around 20-22% in 88 °C-prepared-quick cooking brown rice. Lower digestibility values were determined for 88 °C-treated-INOV CL, and were associated with grain integrity.

Effects of drying temperature and long-term storage conditions on black rice phenolic compounds.

This study aimed to investigate the influence of drying temperatures (20, 40, 60, 80, and 100 °C) followed by 12 months-storage under normal-atmosphere (conventional), nitrogen-atmosphere, and vacuum-atmosphere on black rice phenolics. Increase in drying temperature reduced the total content of free-phenolics, free-flavonoids, and anthocyanins. An increase in bound phenolics extractability was observed at 60 and 80 °C, suggesting some extent of phenolics polymerization and complexation at these drying temperatures. The free fraction of ferulic, caffeic, p-coumaric, and gallic acids were the most thermally unstable compounds. After storage, no reductions were observed only for free caffeic and protocatechuic acids. For total flavonoids, an increase in the free fraction and reduction of the bound fraction were observed in the grains stored under conventional- and vacuum-atmosphere. A reduction of total phenolics occurred regardless of the storage condition. However, storage under nitrogen-atmosphere is the most recommendable condition for maintenance of phenolics in black rice.

Characteristics of starch from different bean genotypes and its effect on biodegradable films.

BACKGROUND: Starches from four common bean genotypes were characterized and used in the production of biodegradable films. Starches were characterized by their swelling power, solubility, amylose content, granule morphology, relative crystallinity, thermal and pasting properties, and susceptibility to α-amylase hydrolysis. Films were characterized according to their morphology, mechanical and water vapor barrier properties, whiteness and opacity. RESULT: Depending on the common bean genotype, a great variation on starch properties was found, which, in turn, clearly impacted on the characteristics of the starch-based films. Starches from BRS Pitanga and BRS Pérola genotypes exhibited the highest amylose content and the lowest swelling capabilities. Bean starch from the IPR Uirapuru genotype presented granules with an irregular surface and shape. Starches from IPR Uirapuru and BRS Estilo genotypes provided well-structured biodegradable films, without the occurrence of fissures or cracks. Moreover, starch films containing starch from BRS Estilo genotype exhibited the highest flexibility, permeability and solubility. CONCLUSION: The morphological, mechanical and water vapor barrier properties of films elaborated with common bean starch vary greatly as a function of the bean genotype used for starch production. © 2018 Society of Chemical Industry.

Physicochemical, pasting, crystallinity, and morphological properties of starches isolated from maize kernels exhibiting different types of defects.

The present study aims to evaluate the physicochemical, rheological, and safety properties of starches isolated from maize kernels with different types of defects. Starch isolation showed to be a valuable alternative to defective yellow maize kernels, since the presence of the evaluated kernel defects (broken, fermented, rotten, moldy, germinated, insect-damaged, and shrunken and immature kernels) did not provide significant changes on starch purity and colour. Only starch isolated from shrunken and immature kernels exhibited reduced extractability. Starch obtained from germinated kernels exhibited the greatest solubility. While flour from moldy kernels showed 7.5 ppb of aflatoxin A1, 25.0 ppb of aflatoxin A2, and 1229.4 ppb of fumonisin B1, any of these mycotoxins were detected in isolated starch. In sum, minor changes in pasting, thermal, crystallinity, and morphological properties of the isolated starches from defective kernels were determined, which does not impair its use in industrial processes.

Immobilization of xylanase and xylanase-ß-cyclodextrin complex in polyvinyl alcohol via electrospinning improves enzyme activity at a wide pH and temperature range.

Xylanase (EC 3.2.1.8) is a key enzyme for degradation of xylan. A limitation of xylanase application in food and beverage industries is the low enzyme activity and stability at a wide pH and temperature range. In the present study, different levels of pure xylanase (XY) and xylanase-ß-cyclodextrin (XY-ß-CD) inclusion complex were immobilized in polyvinyl alcohol (PVA) via electrospinning. Morphological and structural characteristics of obtained fibers were investigated by Fourier-transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyzes. Inclusion complex formation was evaluated by FTIR, XRD, and differential scanning calorimetry (DSC) analyzes. Obtained electrospun fibers showed a smooth surface with average diameter from around 200 to 600 nm. Greater diameters were observed at higher xylanase levels. In addition, inclusion complex provided thicker fibers than pure xylanase. Optimum xylanase activity changed from 60 to 70 °C when enzyme was immobilized in PVA. FTIR results suggest a more efficient enzyme conformation after immobilization. The greatest xylanase efficiency of immobilization was achieved at 0.5%-XY, with specific activity of 59.73 µM/min/mg of immobilized xylanase. Xylanase immobilized in PVA fibers exhibited higher activity at extremer pH conditions (4, 5, 7, and 8), as compared to free xylanase.

Hydrothermal treatment of maize: Changes in physical, chemical, and functional properties.

The objective of this work was to assess the effects of a traditional parboiling treatment on physical, chemical and functional properties of yellow maize kernels. For this, maize kernels were subjected to the three main stages of a traditional parboiling process (soaking, steaming, and drying) at different moisture contents (15%, 25%, or 35%), and different pressure steaming times (0, 15, or 30 min). Kernels were evaluated for physical and chemical changes, while manually generated endosperm fractions were further evaluated for nutritional and functional changes. The parboiling process negatively altered the maize kernels properties by increasing the number of kernels with burst pericarp and decreasing the total carotenoid content in the endosperm by 42%. However, the most intense conditions (35% moisture and 30 min steam) lowered the number of broken kernels by 41%, and the number of stress cracks by 36%. Results also demonstrated that soaking enhanced the nutritional value of soaked yellow maize by increasing the thiamine content and the bound phenolic content in the endosperm fraction up to 102%. The proper implementation of this hydrothermal treatment could lead to significant enhancements in nutritional and functionality of maize products.

Quality of black beans as a function of long-term storage and moldy development: Chemical and functional properties of flour and isolated protein.

The aim of this study was to evaluate the effects of moisture content and storage temperature on the percentage of moldy and fermented beans, mycotoxins levels, phenolic acids content, pasting properties of whole flour, as well as functional and thermal properties of protein isolates from black beans stored for 12 months. Beans stored under 14%/32 °C exhibited 16% of fermented grains, while at 17%/25 °C (42.3%) and 17%/32 °C (93.5%) of moldy plus fermented grains, named drastic conditions (DC). Mycotoxins were not present in grains from all storage conditions. Reduction of gallic, caffeic, and p-hydroxybenzoic acid contents, and increase of sinapic acid were observed in DC. Reduction of peak, final, and setback viscosities of bean flours in DC indicate the application in refrigerated and frozen products. The increase in foaming and reduction in foam degradation of the proteins highlights their use in beverages where the foam is an important factor.

Cooking quality properties and free and bound phenolics content of brown, black, and red rice grains stored at different temperatures for six months.

The changes in cooking quality and phenolic composition of whole black and red rice grains stored during six months at different temperatures were evaluated. Brown rice with known cooking quality properties and low phenolic levels was used for purposes comparison. All rice genotypes were stored at 13% moisture content at temperatures of 16, 24, 32, and 40°C. Cooking time, hardness, free and bound phenolics, anthocyanins, proanthocyanidins, and free radical scavenging capacity were analysed. The traditional rice with brown pericarp exhibited an increase in cooking time and free phenolics content, while rice with black pericarp exhibited a reduction in cooking time after six months of storage at the highest studied temperature of 40°C. There as increases in ferulic acid levels occurred as a function of storage temperature. Red pericarp rice grains showed decreased antioxidant capacity against ABTS radical for the soluble phenolic fraction with increased time and storage temperature.

Effects of Organic and Conventional Cropping Systems on Technological Properties and Phenolic Compounds of Freshly Harvested and Stored Rice.

This study compared the physicochemical and technological properties of the IRGA 410 rice cultivar, obtained from organic and conventional cropping systems, and showed its susceptibility to changes during storage at 0, 6, and 12 mo. The rice conventional cropping system exhibited greater protein, lipids, and ash levels, and a head rice yield. However, organic rice presented greater total carbohydrates, soluble protein, amylose content, 33% greater free phenolics, and phenolic acids, but exhibited a greater percentage of stained grains during the storage period. The free phenolic content of cooked rice was lower than the free phenolic content of the raw rice. By Liquid chromatography with mass spectrometer (LC-MS) were identified p-coumaric and ferulic acids in both fractions (free and bound). The content of p-coumaric acid and ferulic acid in bound fraction was higher in organic brown rice than in conventional brown rice. At 6 and 12 mo of storage, the main fungi found were Aspergillus sp. and Penicillium sp. Prior to storage, the Bipolaris sp. fungi was identified only in organic rice. For conventional rice, the infestation level by Aspergillus sp. increased from 3% to 70% at the 6th mo of storage. In addition to the advantage of organic rice being free of agrochemicals, this study revealed that natural plant defense compounds could be produced when the rice was subjected to more biotic and abiotic stresses. However, some disadvantages were observed, such as lower protein content and a greater percentage of soluble protein, which favored the breaking of rice in processing, and a greater percentage of grain stained before and during storage. PRACTICAL APPLICATION: The organic and conventional cropping systems affect the physicochemical and technological properties of rice grains, which is one of the main cereals grown and consumed in the world. This study shows the advantages and disadvantages of the cropping system in grain properties that are in the interest of both consumers and processing industries.

Foliar Desiccators Glyphosate, Carfentrazone, and Paraquat Affect the Technological and Chemical Properties of Cowpea Grains.

The effects of the use of glyphosate (GLY), glyphosate plus carfentrazone (GLY/CAR), and paraquat (PAR) as plant desiccators on the technological and chemical properties of cowpea grains were investigated. All studied desiccants provided lower cooking time to freshly harvested cowpea. However, the coat color of PAR- and GLY/CAR-treated cowpea was reddish in comparison to the control treatment. Principal component analysis (PCA) from liquid chromatography-mass spectrometry (LC-MS) data sets showed a clear distinction among cowpea from the different treatments. Catechin-3-glucoside and epicatechin significantly contributed for discriminating GLY-treated cowpea, while citric acid was responsible for discriminating GLY/CAR-treated cowpea. Quercetin derivative and gluconic acid were responsible for discriminating control treatment. Residual glyphosate and paraquat content was higher than the maximum limits allowed by Codex Alimentarius and the European Union Commission. Improvements in the technological and chemical properties of cowpea may not be overlapped by the risks that those desiccants exhibit when exceeding the maximum limits of tolerance in food.

Improvement of the quality of parboiled rice by using anti-browning agents during parboiling process.

Browning occurs in parboiled rice as a result of the Maillard reaction that negatively affects consumers' acceptability. The aim of this study was to evaluate the ability of gallic acid, glycine, reduced glutathione and l-cysteine at 0.1, 0.5, 1.0 and 2.0% levels to inhibit browning reactions during the parboiling of rice. Gallic acid and l-cysteine did not exhibit browning inhibition effect at the studied levels. On the other hand, glycine and the higher concentrations of reduced glutathione (1.0 and 2.0%) were able to promote a whiter color and a low free 5-hydroxymethyl-2-furaldehyde content (HMF). The highest level of 2.0% for glycine and reduced glutathione favored protein extractability and a weaker protein-starch matrix, roughly increasing the broken grains percentage. Cooking time changed just for reduced glutathione-treated rice, as a result of their weaker protein-starch matrix and the greater ability of the grains to soften during cooking.

Black bean (Phaseolus vulgaris L.) protein hydrolysates: Physicochemical and functional properties.

Black bean protein hydrolysates obtained from pepsin and alcalase digestions until 120min of hydrolysis were evaluated by gel electrophoresis, relative fluorescence intensity, emulsifying properties, light micrograph of emulsions and in vitro antioxidant activity. The emulsion stability of the bean protein hydrolysates were evaluated during 30days of storage. The pepsin-treated bean protein hydrolysates presented higher degree of hydrolysis than the alcalase-treated protein hydrolysates. The alcalase-treated bean protein hydrolysates showed higher surface hydrophobicity. Moreover, the protein hydrolysates obtained with alcalase digestion presented higher emulsion stability during 30-days than those obtained from pepsin digestion. The protein concentrate and especially the hydrolysates obtained from alcalase digestion had good emulsion stability and antioxidant activity. Thus, they could be exploited as protein supplements in the diet as nutritional and bioactive foods.

Molecular structure, functionality and applications of oxidized starches: A review.

During oxidation, the hydroxyl groups of starch molecules are first oxidized to carbonyl groups, then to carboxyl groups. The contents of the carbonyl and carboxyl groups in a starch molecule therefore indicate the extent of starch oxidation. The mechanisms of starch oxidation with different oxidizing agents, including sodium hypochlorite, hydrogen peroxide, ozone and sodium periodate, are described in this review. The effects of these oxidizing agents on the molecular, physicochemical, thermal, pasting and morphological properties of starch are described as well. In addition, the main industrial applications of oxidized starches are presented. The present review is important for understanding the effects of oxidation on starch properties, and this information may facilitate the development of novel oxidized starches for both food and non-food applications.

Starch digestibility and molecular weight distribution of proteins in rice grains subjected to heat-moisture treatment.

The objective of this study was to evaluate the effects of the heat-moisture treatment (HMT) applied to paddy rice grains on the physicochemical properties, in vitro starch digestibility, and molecular weight distribution of proteins in rice flour. The paddy rice grains were adjusted to 13%, 16%, and 18% moisture and autoclaved at 121°C for 30 and 60min. The HMT promoted a reduction of the amylose content, the swelling power, and the solubility of the rice flour. Changes in the relative crystallinity and molecular weight of the proteins extracted with a sodium phosphate buffer containing 2.0% sodium dodecyl sulfate (SDDS) were observed in HMT samples. The different methods for the quantification of resistant starch resulted in distinct resistant starch contents. The HMT (18%-60min) promoted an increase in resistant starch content and the HMT (16%-60min) caused an increase in the slowly digestible starch in the rice flour.

Extrusion of Rice, Bean and Corn Starches: Extrudate Structure and Molecular Changes in Amylose and Amylopectin.

The objective of this study was to evaluate the effects of starch source and amylose content on the expansion ratio, density, and texture of expanded extrudates, as well as to investigate the structural and molecular changes that occur in starch granules as a function of extrusion. The starches employed were rice starches (8%, 20%, and 32% amylose), carioca bean starch (35% amylose), and Hylon V® corn starch (55% amylose). The extrudates from rice starches containing 20% and 32% amylose exhibited the highest expansion ratio, while, extrudates from Hylon V® corn starch containing 55% amylose exhibited the lowest expansion ratio. The hardness values of the extrudates with 55% amylose were twice those of the extrudates with 20%, 32%, and 35% amylose. An additional finding was that although the amylopectin promoted the expansion of the gelatinized starch matrix, it failed to strengthen and sustain the walls of the extrudate bubbles during expansion.

The revisited levels of free and bound phenolics in rice: Effects of the extraction procedure.

The effects of the type of solvolytic solution and number of extraction steps on the recovery of free phenolics, anthocyanins and proanthocyanidins from different rice samples were evaluated. Moreover, bound phenolic acids were determined as a function of enzymatic and/or alkaline hydrolysis treatment of the rice residue obtained after the extraction of free phenolics. The Acetone/Water (70:30 v/v) was the most effective solvolytic solution for extracting free phenolics from pigmented rice, as well as anthocyanins from black and wild rice, and proanthocyanidins from red rice. The application of three extraction steps increased the recovery of free phenolics up to 10%. The adoption of an enzymatic treatment, with α-amylase in order to reduce the paste viscosity of the residue, increased the extractability of bound phenolics. α-Amylase at 37°C during 15min followed by an alkaline hydrolysis at 37°C was the best treatment for the recovery of bound phenolics.

Changes in the Bioactive Compounds Content of Soybean as a Function of Grain Moisture Content and Temperature during Long-Term Storage.

Soybean is a rich source of bioactive compounds, such as phenolic acids, flavonoids, isoflavones, carotenoids, and tocopherols. The amount of bioactive compounds in freshly harvested soybeans and their derived products has been determined; however, when they are used in the food industry, soybeans are generally stored prior to being processed. This study aimed to evaluate the effects of soybean moisture content (12%, 15%, and 18%) and storage temperature (11, 18, 25, and 32 °C) on the free phenolic, total flavonoid, vanillic acid, total carotenoid, and δ- and γ-tocopherol content of soybeans stored for 12 mo. Moreover, the ABTS and DPPH radical scavenging activities of phenolic extracts were determined. There was an increase in free phenolics and total flavonoids in the stored grains compared with the grains on the 1st d of storage. Vanillic acid showed a decrease in soybeans stored at 15% and 18% moisture content and 25 or 32 °C, which indicated some degradation into other metabolites. Total carotenoid content decreased as a function of storage temperature and showed some temperature-dependent degradation. The δ- and γ-tocopherol content also tended to decrease in grains stored at 15% or 18% moisture content or 25 or 32 °C, regardless of the moisture content studied.

Polishing and parboiling effect on the nutritional and technological properties of pigmented rice.

This study aims to evaluate the effects of polishing and parboiling on proximate composition, structure, phenolic compounds, antioxidant activity, cooking time and hardness of IAC-600 black rice cultivar and MPB-10 red rice lineage. Proximate analysis and light micrographs revealed higher migration of red rice proteins than black rice proteins to the endosperm as a result of parboiling. Parboiling reduced the ash content of red rice while no difference was determined in black rice. Gelatinized starch granules from both genotypes showed similar appearance. There was a decrease in relative crystallinity on both black and red rice subjected to parboiling, which was an indicative of crystallites disruption. Polishing removed more than 90% of free phenolics for both genotypes, while parboiling allowed the partial preservation of free phenolics content in polished rice. Parboiling induced an increase in the cooking time of red rice, but a decrease in the cooking time of black rice.