Effect of removing cadmium with citric acid on the physicochemical and microstructure properties of rice bran

Mitigation strategies for excessive cadmium in rice

Cadmium (Cd)-contaminated rice is a human food safety problem that lacks a clear solution. A large amount of rice having an excessive Cd content is processed yearly, but it cannot be discarded and placed in landfills because it will cause secondary pollution. How do we best cope with this toxic rice? From the perspectives of food safety, food waste prevention, and human hunger eradication, the use of contemporary physical, chemical, and biological techniques to lower the Cd content in postharvest Cd-contaminated rice so that it can be used safely is the best course of action. In this review, the contamination, chemical speciation, and distribution of Cd in rice are analyzed and discussed, as are the methods of Cd removal from rice, including a comparison of the advantages and disadvantages of various techniques. Owing to the limitations of current technology, research and technological development recommendations for removing Cd from rice grain are presented. The chemical and biological methods produce higher Cd-removal rates than physical methods. However, they are limited to small-scale laboratory applications and cannot be applied on a large industrial scale. For the efficient safe removal of Cd from food, mixed fermentation with lactic acid bacteria and yeast has good application prospects. However, limited strains having high Cd-removal rates have been screened. In addition, modern biotechnology has rarely been applied to reduce rice Cd levels. Therefore, applying genetic engineering techniques to rapidly obtain microorganisms with high Cd-removal rates in rice should be the focus of future research.

Effect of gluconic acid rinsing on cadmium decontamination from rice protein

Cadmium (Cd) accumulation in rice protein has long been considered a significant threat to human health. In the present study, a costless and effective method based on gluconic acid (GA) rinsing of rice protein was developed to reduce Cd contamination in rice protein. Moreover, the effect of GA on the structural and functional properties of rice protein was evaluated. With liquid-solid ratio of 30 mL/g and oscillation time of 120 min, 96.0% and 93.6% of Cd were eliminated from rice protein-H and rice protein-L, respectively. In addition, the results of scanning electron microscopy, Fourier transform infrared, and sodium dodecyl sulfate polyacrylamide gel electrophoresis analyses showed that GA treatment did not significantly change the structural properties of rice protein. However, GA treatment increased foaming properties, water holding capacity, and oil holding capacity of the rice protein, without affecting its further applicability. Thus, the proposed GA rinsing method can be considered a green and efficient strategy to solve the issue brought by Cd residual contamination in rice protein. PRACTICAL APPLICATION: Given the advantages of green and efficient agriculture, gluconic acid (GA) has emerged as a powerful strategy for removing the Cd from rice protein. The method developed herein showed great potentials for applications in the manufacture of rice-based products.

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.

Synergistic effects of rice straw and rice bran on enhanced methane production and process stability of anaerobic digestion of food waste

This study investigated the synergistic effects of rice straw (RS) and rice bran (RB) addition on methane production and process stability of anaerobic digestion of food waste (FW). Positive synergistic effect (Synergy index (SI) = 1.03-1.24 > 1) was noticed in all the co-digestion reactors. The optimum mixing ratio of FW:RS:RB (volatile solid (VS) basis) was 60:10:30 with the maximum SI (1.24), achieving 27.4% increase in methane yield (235.4 mL/g-VS) and around 5 days shorter of λ (3.7 days) compared to the mono-digestion of FW (184.8 mL/g-VS and 8.2 days). Remarkably high concentration of volatile fatty acids (VFAs) was also accumulated in the mono-digestion of FW, especially propionic acid, which to a great extent caused the methane production to stagnate. Results from this study demonstrate that co-digestion of FW and RS with RB has high potentials for energy recovery from AD of the mixed feedstocks and its stable operation.

Accumulation potential and tolerance response of Typha latifolia L. under citric acid assisted phytoextraction of lead and mercury

Chelate-assisted phytoextraction by high biomass producing macrophyte plant Typha latifolia L. commonly known as cattail, is gaining much attention worldwide. The present study investigated the effects of Lead (Pb) and Mercury (Hg) on physiology and biochemistry of plant, Pb and Hg uptake in T. latifolia with and without citric acid (CA) amendment. The uniform seedlings of T. latifolia were treated with various concentrations in the hydroponics as: Pb and Hg (1, 2.5, 5 mM) each alone and/or with CA (5 mM). After four weeks of treatments, the results revealed that Pb and Hg significantly reduced the plant agronomic traits as compare to non-treated plants. The addition of CA improved the plant physiology and enhanced the antioxidant enzymes activities to overcome Pb and Hg induced oxidative damage and electrolyte leakage. Our results depicted that Pb and Hg uptake and accumulation by T. latifolia was dose depend whereas, the addition of CA further increased the concentration and accumulation of Pb and Hg by up to 22 & 35% Pb and 72 & 40% Hg in roots, 25 & 26% Pb and 85 & 60% Hg in stems and 22 & 15 Pb and 100 & 58% Hg in leaves respectively compared to Pb and Hg treated only plants. On other hand, the root-shoot translocation factor was ≥1 and bioconcentration factor was also ≥2 for both Pb & Hg. The results also revealed that T. latifolia showed greater tolerance towards Hg and accumulated higher Hg in all parts compared with Pb.

Reducing the cadmium, inorganic arsenic and dimethylarsinic acid content of rice through food-safe chemical cooking pre-treatment

Cadmium, inorganic arsenic and, potentially, dimethyl arsenic acid are carcinogens widely elevated in rice. Here it was identified that the food-safe and common cadmium chelator citric acid efficiently removed cadmium from intact grain via pre-soaking procedure, while also reducing arsenic species. A twostep pre-soaking stage was developed whereby rice was first incubated, at ambient temperature, in 1 M citric acid for 12 h, and then in 1 M calcium carbonate for another 12 h, the latter step to neutralize pH, followed by cooking. When 10 different individual types of rice were processed in such a way this resulted in removal rates of 79% for cadmium, 81% for inorganic arsenic and a 66% for DMA. The technology is particularly suitable for bulk food processing and could be deployed in the most cadmium and arsenic impacted regions where rice is a staple.

Rice intercropping with alligator flag (Thalia dealbata): A novel model to produce safe cereal grains while remediating cadmium contaminated paddy soil

Phytoremediation has been employed as a cost-effective technique to remove the cadmium (Cd) from soil and water in several ecosystems. However, little is known about whether intercropping the remediating plants with rice (Oryza sativa) crop could reduce Cd accumulation in rice grains. We conducted greenhouse pot and concrete pond trials to explore the effects of intercropping alligator flag (Thalia dealbata, Marantaceae) on soil Cd remediation, paddy soil and microbial properties, and rice production. Our results suggest that intercropping with alligator flag significantly decreased Cd absorption, transportation, and accumulation from the soil to the rice grains (under 0.2 mg kg^-1 at a soil Cd content below 2.50 mg kg^-1). This decrease was due to the lowered Cd availability and higher soil pH in the rice-alligator flag intercropping system. Although planting alligator flag resulted in the reduction of soil NH₄-N and NO₃-N, Cd content in the rhizosphere was the main factor restricting microbial biomass, species, and community composition. Alligator flag could tolerate higher Cd contamination, and accumulate and stabilize more Cd in its tissues than rice. Our study suggests that alligator flag intercropped with rice has potential as a phytostabilization plant to produce rice safely for human consumption in moderately Cd-contaminated soils.

Rice bran attenuated obesity via alleviating dyslipidemia, browning of white adipocytes and modulating gut microbiota in high-fat diet-induced obese mice

Obesity has become an international public health problem. In this study, an obese mice diet was supplemented with raw rice bran (RRB) or infrared radiation-stabilized rice bran (IRRB) to investigate the attenuation of obesity induced by a high-fat diet. Mice were fed a normal diet or a high-fat diet with and without rice bran supplementation (300 mg per kg body weight per day) by oral gavage for 39 days to investigate the obesity preventive effect. The results indicate that different rice bran supplements reduced body weight, relative adipose tissue weight, inflammation, and serum parameters, and relieve liver steatosis to varying degrees. The data of real-time qPCR and western blots (WB) showed that rice bran activated brown adipose tissue (BAT) and increased white adipose tissue (WAT) browning. Rice bran also reduced the ratio of Firmicutes/Bacteroidetes and enhanced the relative abundance of Akkermansia. In summary, our findings suggest that rice bran intervention played a significant role in reducing dyslipidemia, alleviating inflammation, enhancing thermogenesis and modulating gut microbiota for the prevention and control of obesity.