Hari Niwas Mishra

A Review on Biological Control and Metabolism of Aflatoxin

The series of events that led to the discovery of aflatoxin as a potent carcinogen, its biosynthesis, mechanism of action, structure-function relationship provide interesting insight into the economical and technological factors involved in the development of an effective control measure for the toxin. Scientists all over the world are making continuous efforts to explore a generalized process of detoxification, which can bring down the toxin content in heterogeneous commodities to a threshold level. In this article biological control methods with special emphasis on in vivo and in vitro enzymatic detoxification of aflatoxin have been reviewed. Future areas of research involving large-scale enzymatic detoxification and modified atmosphere storage are also discussed. Referee: Dr. F. S. Chu, 16458 Denhave Court, Chino Hills, CA 91709

Fermented Milks and Milk Products as Functional Foods—A Review

Fermented foods and beverages possess various nutritional and therapeutic properties. Lactic acid bacteria (LAB) play a major role in determining the positive health effects of fermented milks and related products. The L. acidophilus and Bifidobacteria spp are known for their use in probiotic dairy foods. Cultured products sold with any claim of health benefits should meet the criteria of suggested minimum number of more than 106 cfu/g at the time of consumption. Yoghurt is redefined as a probiotic carrier food. Several food powders like yoghurt powder and curd (dahi) powder are manufactured taking into consideration the number of organisms surviving in the product after drying. Such foods, beverages and powders are highly acceptable to consumers because of their flavor and aroma and high nutritive value. Antitumor activity is associated with the cell wall of starter bacteria and so the activity remains even after drying. Other health benefits of fermented milks include prevention of gastrointestinal infections, reduction of serum cholesterol levels and antimutagenic activity. The fermented products are recommended for consumption by lactose intolerant individuals and patients suffering from atherosclerosis. The formulation of fermented dietetic preparations and special products is an expanding research area. The health benefits, the technology of production of fermented milks and the kinetics of lactic acid fermentation in dairy products are reviewed here.

High-Pressure Inactivation of Enzymes: A Review on Its Recent Applications on Fruit Purees and Juices

In the last 2 decades high-pressure processing (HPP) has established itself as one of the most suitable nonthermal technologies applied to fruit products for the extension of shelf-life. Several oxidative and pectic enzymes are responsible for deterioration in color, flavor, and texture in fruit purees and juices (FP&J). The effect of HPP on the activities of polyphenoloxidase, peroxidase, β-glucosidase, pectinmethylesterase, polygalacturonase, lipoxygenase, amylase, and hydroperoxide lyase specific to FP&J have been studied by several researchers. In most of the cases, partial inactivation of the target enzymes was possible under the experimental domain, although their pressure sensitivity largely depended on the origin and their microenvironmental condition. The variable sensitivity of different enzymes also reflects on their kinetics. Several empirical models have been established to describe the kinetics of an enzyme specific to a FP&J. The scientific literature in the last decade illustrating the effects of HPP on enzymes in FP&J, enzymatic action on those products, mechanism of enzyme inactivation during high pressure, their inactivation kinetics, and several intrinsic and extrinsic factors influencing the efficacy of HPP is critically reviewed in this article. In addition, process optimization of HPP targeting specific enzymes is of great interest from an industrial approach. This review will give a fair idea about the target enzymes specific to FP&J and the optimum conditions needed to achieve sufficient inactivation during HPP treatment.

YOGHURT POWDER—A REVIEW OF PROCESS TECHNOLOGY, STORAGE AND UTILIZATION

Yoghurt powders possess various nutritional and therapeutic values. Antitumour activity is associated with the cell wall of starter bacteria and so the activity remains even after drying. The primary objective of drying yoghurt is to preserve it in a shelf-stable powdered form of high quality without a need for refrigeration. Such powder can be prepared by various methods, such as freeze-drying, spray-drying, microwave-drying and vacuumdrying. Before drying, it is beneficial to concentrate yoghurt by methods including cloth bag method, mechanical, centrifugation, ultrafiltration and vacuum concentration. S. thermophilus shows less sensitivity in comparison to L. bulgaricus, during freeze- as well as spray-drying of yoghurt. Cultured products sold with any claims of health benefits should meet the criteria of suggested minimum number of more than 106 cfu g–1 at the expiry date. Freeze-dried yoghurt can be stored for up to 1–2 years at 4°C. After 1 year of storage, the powder typically contains total bacterial counts of 106 cfu g–1. Active cultures are guaranteed for 1 year under cool, dry conditions for spray-dried yoghurt; it can be used in the bakery and confectionary industries.

Magnetic Ni/Ag core–shell nanostructure from prickly Ni nanowire precursor and its catalytic and antibacterial activity

A microemulsion template assisted hydrazine hydrate mediated wet chemical reduction of nickel chloride hexahydrate at 70 °C has been used for the fabrication of prickly nickel nanowires. Subsequently, the nanowire surfaces are modified with silver using the well known Tollens reagent to form Ni/Ag core–shell nanostructures. X-Ray diffraction studies confirm the formation of face centered cubic type structures of nickel as well as silver in Ni/Ag nanostructures individually and they are found to be devoid of any trace of contamination. Low magnification field emission scanning electron microscope (FESEM) images confirm the wire-like morphology of nickel as well as Ni/Ag core–shell nanostructures. However, the high magnification FESEM and transmission electron microscopy images show the prickly surface of nickel nanowires consisting of cone-like nanostructures, where small spherical silver particles are deposited. Vibrating sample magnetometer (VSM) studies show well defined ferromagnetic behavior of the Ni as well as core–shell Ni/Ag structures. In addition, these nanostructures have been proved to be efficient catalysts at room temperature for the reduction of p-nitrophenol compared to bare Ni nanowires, and the magnetic behaviour serves as an added advantage in its easy separation from the reaction mixture so that it can be reused. Furthermore, Ni/Ag nanostructures also exhibit excellent antibacterial properties, which are significantly better than commercially available antibacterial materials.

Ultrasound for Improved Crystallisation in Food Processing

Within the food industry, controlling crystallisation is a key factor governing food structure, texture and consumer appeal, with some foods requiring the promotion of crystallisation in a controlled manner (e.g. chocolate) and others a check (e.g. honey). Sonocrystallisation is the application of ultrasound energy to control the nucleation of a crystallisation process. The use of power ultrasound provides a useful approach to producing crystals with desired properties. Sonocrystallisation facilitates process control by modulating crystal size distribution and morphology. This paper details the governing mechanisms of sonocrystallisation. Proven and potential applications of the process in foods are reviewed including chocolate, honey, fats and frozen foods. Challenges of process adoption such as scale-up are discussed.

Optimization of Mango Soy Fortified Yogurt Formulation Using Response Surface Methodology

Abstract The response surface methodology (RSM) was used to optimize the formulation of mango soy fortified yogurt (MSFY). The independent variables were proportions of mango pulp (1.2–13.8%), soymilk (2.39–27.61%), and fat content (0.48–5.52%) of buffalo milk. The responses were overall acceptability rating, counts of Streptococcus thermophilus and Lactobacillus bulgaricus and hardness of the product. Statistical analysis revealed that mango pulp, soymilk, and fat content of buffalo milk significantly affected (95% confidence level) all the responses. Contour plots for each response were used to generate an optimum area by superimposition. Model validation was conducted using separate experiments at optimum conditions. The optimum formulation conditions of 7.1 kg mango pulp (18% total solids), 14.7 kg soymilk (8.2% total solids), and 78.2 kg buffalo milk (2.95% fat content and 9% solid not fat) per 100 kg are recommended for the blend formulation yielding an acceptable and good quality MSFY.

Effect of aflatoxin B1 detoxification on the physicochemical properties and quality of ground nut meal

Abstract Aflatoxin B 1 (AFB 1 ) in groundnut meal (GNM) was detoxified up to 97% by a combination of enzymatic and physical processes. Finely-powdered defatted groundnut meal containing 1.2 mM AFB 1 per 100 g of meal was first detoxified up to 53% with 10 IU of horseradish peroxidase enzyme in the presence of hydrogen peroxide and then the meal containing 12–15% (wb) moisture was treated with microwave radiation at 1 kwt for 15 min to achieve a final 97% detoxification. A comparison was made of the treated and untreated groundnut meal quality with respect to their nitrogen solubility, total nitrogen and protein nitrogen contents, and protein composition. Rat feeding experiments were performed to study the effect of detoxification processes on ground nut meal quality as indicated by the mortality, food efficiency ratio and food conversion rate. Mean weight gains of the rats receiving the treated meals were essentially comparable to those for animals receiving aflatoxin-free diets. Overall, nitrogen-solubility of the enzyme-treated meal increases in the pH 2–6 range. Polyacrylamide gel electrophoretic patterns of the protein did not show any notable changes. Amount of protein nitrogen in the meal increased after the enzymatic treatment. Mortality rates of the young animals were high when they were fed untreated meal containing aflatoxin. Resistance increased with age, which was evidenced by the relatively lower mortality rate of the rats after prolonged feeding of aflatoxin-infected meal.

Fourier Transform Near-Infrared Spectroscopy for rapid and simple determination of phytic acid content in green gram seeds (Vigna radiata).

The feasibility of measuring phytic acid content in green gram (Vigna radiata) seeds was investigated by Fourier Transform Near-Infrared (FT-NIR) spectroscopic technique. Pure phytic acid standards of varying concentrations were scanned using FTNIR spectroscopy. The spectra were measured in diffused reflectance mode by keeping 100-1500 mg/100g standard of pure phytic acid in small sample cuvette. A calibration model was developed using pure phytic acid standards of varying concentrations in the near-infrared region (4000-12,000 cm(-1)). FT-NIR spectroscopy with chemometrics, using the first derivative plus vector normalisation method could predict the phytic acid content in green gram seeds samples. The developed model was validated using cross-validation technique. Maximum coefficient of determination (R(2)) value of 0.97 was obtained for the calibration model developed. The developed model was applied to predict phytic acid content in green gram seeds samples within 1-2 min. The developed procedure was further validated by recovery studies by comparing with UV spectroscopic method of phytic acid determination.

Microwave drying for safe storage and improved nutritional quality of green gram seed (Vigna radiata).

The present study describes the effect of the microwave-heating method on disinfestations and physico characteristics, viz., grain size, grain hardness, and nutritional quality, of the stored green gram seed. It has been observed that the use of the microwave-heating method not only prolongs the storage duration of the green gram seed but also enhances its nutritional quality. The effect of independent parameters, viz., microwave power level and time of exposure, on the moisture content, insect mortality, color, and antinutrient factor (phyic acid) was optimized using response surface methodology (RSM), with the optimized value for power of 808 W and time at 80 s. The optimally treated green gram seed has 8.9% moisture, 99.5% insect mortality, 2.22 Δa* (green color of seed), and 591.79 mg/100 g of antinutrient factor (phytic acid). The grain size (geometric mean diameter, D(m)) of the control (untreated) sample was 3.75 mm, and that of the microwave-treated sample using optimum conditions was 3.99 mm. The grain hardness of the control sample was 3.31 kg, and that of the microwave-treated sample using optimum conditions was 1.305 kg. In vitro protein digestibility (IVPD) of the control (untreated) sample was 83 ± 0.289%, and that of the microwave-treated sample using optimum conditions was 85 ± 0.296%. These values are significantly difference (p < 0.05). The mineral elements studied were Zn, Fe, Mg, Mn, Cu, K, Ca, and Na. The microwave treatment resulted in a non-significant (p < 0.05) effect for Mg, Mn, Cu, K, and Na but a significant (p < 0.05) effect for Zn, Ca, and Fe. The results indicate that the microwave heating not only increases the insect mortality but also reduces the moisture content and antinutritional factor (phytic acid), while the natural green color of the seed is not affected much. This study provides a novel and environmentally safe technique and increase in the nutritive quality.