Effects of microwave roasting on physicochemical properties of pistachios (Pistaciavera L.)

Use of X-Irradiations in Reducing the Waste of Aflatoxin-Contaminated Pistachios and Evaluation of the Physicochemical Properties of the Irradiated Product

This study investigates the effects of electron beam irradiation (0, 1, 2, 4, and 6 kGy) on Aspergillus flavus, aflatoxin B1 (AFB1), and the physicochemical properties of pistachios. The findings suggested that e-beam significantly reduced the spore population of A. flavus and the concentration of AFB1 at doses of 4 and 6 kGy. Three AFB1 degradation products were detected via LC-MS analysis and their structures were presented. Total phenolic content was improved at a dose of 2 kGy, while antioxidant activity was decreased in all treatments in both DPPH and ABTS assays. The chlorophyll and carotenoid content declined and the color indices changed, leading to a darker color. E-beam at a dose of 2 kGy raised the soluble protein levels and changed the intensity and pattern of protein bands. Irradiation doses of up to 6 kGy enhanced the content of malondialdehyde and total saturated fatty acids while leading to a decline in unsaturated fatty acids. The quality features were adversely affected at doses > 4 kGy. The findings suggest that as an alternative method, e-beam at doses ≥ 2 kGy can effectively decrease fungal load and aflatoxin B1 contamination, and e-beam application at doses ≤ 2 kGy can maintain the physicochemical attributes of pistachios to an acceptable extent.

Impact of different microwave treatments on food texture

Electromagnetic waves are frequently used for food processing with commercial or domestic type microwave ovens at present. Microwaves cause molecular movement by the migration of ionic particles or rotation of dipolar particles. Considering the potential applications of microwave technique in food industry, it is seen that microwaves have many advantages such as saving time, better final product quality (more taste, color, and nutritional value), and rapid heat generation. Although microwave treatment used for food processing with developing technologies have a positive effect in terms of time, energy, or nutrient value, it is also very important to what extent they affect the textural properties of the food that they apply to. For this purpose, in this study, it has been investigated that the effects of commonly used microwave treatments such as drying, heating, baking, cooking, thawing, toasting, blanching, frying, and sterilization on the textural properties of food. In addition, this study has also covered the challenges of microwave treatments and future work. In conclusion, microwave treatments cause energy saving due to a short processing time. Therefore, it can be said that it affects the textural properties positively. However, it is important that the microwave processing conditions used are chosen appropriately for each food material.

Roasted fox nuts (Euryale Ferox L.) contain higher concentration of phenolics, flavonoids, minerals and antioxidants, and exhibit lower Glycemic Index (GI) in human subjects

Fox nut (Euryale ferox) is categorized among superior quality foods because of its highly nutritious profile. It also serves as a good protein source for vegetarian diets. However, it is not widely consumed, due to soggy texture and bland flavor as compared to other nuts. In this study, we used roasting and seasoning to enhance its consumer acceptance. Furthermore, we have also compared biochemical, nutritional and physical properties of the roasted and unroasted fox nuts; and their Glycemic Index (GI) in human subjects. Results showed that roasting significantly (P ≤ 0.05) improved the minerals content (from 0.58 to 0.66%), protein content (from 11.40 to 14.57%), total phenolics (from 346.02 to 470.62 mg GAE/100 g), flavonoids (from 4.15 to 4.43 mg CE/g), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (from 48.54 to 79.13% inhibition) and Ferric Reducing Antioxidant Power (from 662.46 to 957.14 μmol FeSO4/g). Consumer acceptance was evaluated with and without seasoning; both salt and spice seasoned roasted nuts had greater overall acceptability as compared to plain roasted and unroasted nuts. Fox nuts also reported low GI (37%) in human subjects (ethical approval #1772/01-06-2020). Thus, roasted fox nuts can be consumed as nutrient rich and low GI snack; not only as a component of healthy diet but can also be served to patients with metabolic disorders like obesity and diabetes.

Volatile Profile of Nuts, Key Odorants and Analytical Methods for Quantification

The presence of nuts in diets has notably increased due to their composition, and the presence of antioxidants and their unsaturated fatty acid profile has led to a considerable increase in their consumption. The volatile profile of nuts is important from different points of view. It affects consumer’s selection, influences raw material selection for the production of composite foods, dictates variety selection in breeding programs, and, from a quality perspective, its changes can indicate food degradation or alteration. A review of the published bibliography concerning the determination of volatiles in nuts has been carried out. The information retrieved has been divided into four main sections. First, a discussion on the main volatiles present in nuts is performed; next, a revision of the methods used to determine the volatiles is presented; and, finally, two sections describing how harvesting conditions, healthy state and the thermal treatment of nuts modifies their volatile profile are added. Analysis of the published bibliography denoted the complexity of volatile determination and the different variables that can modify the compounds present in the volatile fraction of nuts.

Elimination of Aspergillus flavus from Pistachio Nuts with Dielectric Barrier Discharge (DBD) Cold Plasma and Its Impacts on Biochemical Indices

In the present research, the effects of different durations (0, 15, 30, 60, 90, 120, 150, and 180 sec) of dielectric barrier discharge (DBD) cold plasma on decontaminating Aspergillus flavus, detoxifying pure aflatoxin B1 (AFB1), and the quality attributes of pistachio nuts (total phenolic content, antioxidant activity, chlorophylls, total carotenoids, instrumental color, total soluble protein, and malondialdehyde determination) were studied. The results showed that the viable spore population reduced with the increase of plasma treatment duration, so that after 180 s of the treatment, a decrease by 4 logs was observed in the spore population. Chlorophyll a and b, as well as total carotenoid levels and color parameters, decreased, which led to darker pistachio samples and intensity reduction in soluble protein content and protein bands. Plasma treatment did not alter the total phenolic content but slightly increased the antioxidant activity of pistachio nuts samples. The malondialdehyde values significantly increased all the plasma treatment durations. The maximum reduction of AFB1 was observed after 180 s of the treatment, which was 64.63% and 52.42% for glass slides and pistachio nut samples, respectively. The present findings demonstrated that cold plasma could be used as an efficient decontamination method of food products without inducing undesirable quality changes in nuts.

Drying methodology effect on the phenolic content, antioxidant activity of Myrtus communis L. leaves ethanol extracts and soybean oil oxidative stability

In this study, different drying methodologies (convective air, oven and microwave) of Myrtus communis L. (M. communis L.) leaves were conducted to investigate their effects on the levels of phenolic compounds, antioxidant capacity of ethanolic extracts (EEs) as well as the soybean oil oxidative stability. Drying methodology significantly influenced the extractability of phenolic compounds. Microwave drying led to an increase in the amounts of total phenols, flavonoids and proanthocyanidins followed by oven drying at 70 °C. Higher temperature of drying (100 and 120 °C) led to a significant reduction of their amounts (p < 0.05). An ultra-performance liquid chromatography method combined with high resolution mass spectroscopic detection was used to analyze the phenolic fraction of extracts. Higher amounts of the identified compounds were observed when leaves were heat treated. Furthermore, the evaluation of the antioxidant activity showed that the studied extracts possess in general high antioxidant capacities, significantly dependent on the employed drying methodology. The incorporation of the different extracts at 200 ppm in soybean oil showed that its oxidative stability was significantly improved. Extracts from leaves treated with microwave (EE_MW) and at 70 °C (EE_70) have better effect than BHT. The results of the present study suggest that microwave drying could be useful to enhance the extractability of phenolic compounds and the antioxidant capacity of M. communis L. leaf extract.

Effects of different roasting methods on formation of acrylamide in pistachio

Drying and roasting are conventional processes in the nut industry. However, roasting as an important procedure in nuts manufacturing may cause some physicochemical changes in nuts. Acrylamide is one of these chemical compounds that is formed due to the roasting process. Acrylamide is known as a neurotoxicant, carcinogen, and reproductive toxicant. In this study, raw and salted pistachios were roasted under three conditions including hot-air, infrared (IR), and microwave methods. Then, 80 pistachio kernels were analyzed by ultra-high-performance liquid chromatography. The results showed that all samples contained different ranges of acrylamide between 57 ± 0.86 and 851 ± 2.8 μg/kg. Besides, raw pistachios and sun-dried pistachios also contained acrylamide, with the amount of 57 ± 0.86 and 93 ± 1.07 μg/kg, respectively. The highest acrylamide amount was found in raw pistachio (unsalted) roasted by IR method, while lower acrylamide amount observed in the microwave method. The amount of acrylamide in salted and roasted pistachios was less than just roasted pistachios under the same conditions. Finally, in all the treatments, increasing temperature, time, voltage, and power lead to an increase in acrylamide levels. The results showed that acrylamide in the roasted pistachios may cause health problems. This study presents a novel investigation in the effects of roasting conditions (temperature, power, voltage, and time) on acrylamide content in pistachios.

Anti-aging potential of tree nuts with a focus on the phytochemical composition, molecular mechanisms and thermal stability of major bioactive compounds

Tree nuts, complete functional foods, contain macro- and micronutrients of high biological value.