Balunkeswar Nayak

Optimization of microwave-assisted extraction of polyphenols from Myrtus communis L. leaves.

Phytochemicals, such as phenolic compounds, are of great interest due to their health-benefitting antioxidant properties and possible protection against inflammation, cardiovascular diseases and certain types of cancer. Maximum retention of these phytochemicals during extraction requires optimised process parameter conditions. A microwave-assisted extraction (MAE) method was investigated for extraction of total phenolics from Myrtus communis leaves. The total phenolic capacity (TPC) of leaf extracts at optimised MAE conditions was compared with ultrasound-assisted extraction (UAE) and conventional solvent extraction (CSE). The influence of extraction parameters including ethanol concentration, microwave power, irradiation time and solvent-to-solid ratio on the extraction of TPC was modeled by using a second-order regression equation. The optimal MAE conditions were 42% ethanol concentration, 500 W microwave power, 62 s irradiation time and 32 mL/g solvent to material ratio. Ethanol concentration and liquid-to-solid ratio were the significant parameters for the extraction process (p<0.01). Under the MAE optimised conditions, the recovery of TPC was 162.49 ± 16.95 mg gallic acidequivalent/gdry weight(DW), approximating the predicted content (166.13 mg GAE/g DW). When bioactive phytochemicals extracted from Myrtus leaves using MAE compared with UAE and CSE, it was also observed that tannins (32.65 ± 0.01 mg/g), total flavonoids (5.02 ± 0.05 mg QE/g) and antioxidant activities (38.20 ± 1.08 μg GAE/mL) in MAE extracts were higher than the other two extracts. These findings further illustrate that extraction of bioactive phytochemicals from plant materials using MAE method consumes less extraction solvent and saves time.

Comparison of microwave, ultrasound and accelerated-assisted solvent extraction for recovery of polyphenols from Citrus sinensis peels

Peel of Citrus sinensis contains significant amounts of bioactive polyphenols that could be used as ingredients for a number of value-added products with health benefits. Extraction of polyphenols from the peels was performed using a microwave-assisted extraction (MAE) technique. The effects of aqueous acetone concentration, microwave power, extraction time and solvent-to-solid ratio on the total phenolic content (TPC), total antioxidant activity (TAA) (using DPPH and ORAC-values) and individual phenolic acids (IPA) were investigated using a response surface method. The TPC, TAA and IPA of peel extracts using MAE was compared with conventional, ultrasound-assisted and accelerated solvent extraction. The maximum predicted TPC under the optimal MAE conditions (51% acetone concentration in water (v/v), 500 W microwave power, 122 s extraction time and 25 mL g(-1) solvent to solid ratio), was 12.20 mg GAE g(-1) DW. The TPC and TAA in MAE extracts were higher than the other three extracts.

Thermal degradation of anthocyanins from purple potato (cv. Purple Majesty) and impact on antioxidant capacity.

Degradation parameters of purified anthocyanins from purple-fleshed potato (cv. Purple Majesty) heated at high temperatures (100-150 °C) were determined. Purified anthocyanins, prepared by removing salts, sugars, and colorless nonanthocyanin phenolics from the crude extract, were monitored and quantified using HPLC and spectrophotometry for heat-induced degradation products. Separation of colorless phenolics from the anthocyanins was confirmed using HPLC at two wavelengths, 280 and 520 nm. The degradation kinetics of purified anthocyanins followed a first-order reaction with reaction rate constants (k values) of 0.0262-0.2855 min(-1), an activation energy of 72.89 kJ/mol, thermal death times (D values) of 8.06-8789 min, and a z value of 47.84 °C over the temperature range of 100-150 °C. The enthalpy and entropy of activation were 59.97 kJ/mol and -116.46 J/mol·K, respectively. The antioxidant capacity in the purified anthocyanins, measured by DPPH and ABTS assays, was increased after the thermal treatment, indicating antioxidant activities of degradation products in the samples.

Effect of Extrusion on the Antioxidant Capacity and Color Attributes of Expanded Extrudates Prepared from Purple Potato and Yellow Pea Flour Mixes

Foods with antioxidant capacity provide protection against cardio-vascular, certain forms of cancers, and Alzheimers diseases caused by oxidative damages and contribute health benefits. The effect of extrusion cooking on the antioxidant capacity and color attributes of extruded products prepared from 3 selected formulations of purple potato and yellow pea flours using a co-rotating twin screw extruder were studied. Expansion ratios of the extruded products varied from 3.93 to 4.75. The total antioxidant capacities (TAC) of the extruded products, using DPPH assay, were 3769 to 4116 μg trolox equivalent/g dry weight sample and not significantly different (P > 0.05) from their respective raw formulations. The total phenolic contents (TP) of the extruded products varied from 2088 to 3766 μg of gallic acid equivalent/g dry weight sample and retained 73% to 83% of the TP from the raw formulations after extrusion. The total anthocyanins contents (TA) in the extrudates were 0.116 to 0.228 mg of malvidin-3-glucosides/g dry weight sample. Compared with their raw formulations, significant losses (60% to 70%) of the TA in the extruded products occurred due to extrusion cooking. Browning indices and color attributes such as brightness, chroma, and hue angle agreed with degradation of anthocyanins in the extruded products. However, extrusion cooking retained antioxidant capacities of the raw formulations in the extruded products either in their natural forms or degraded products with radical scavenging activity. This study demonstrated the potential for the production of puffed extruded food products with the improved antioxidant content from colored potatoes and pulse formulations.

Bioactivity of Antioxidants in Extruded Products Prepared from Purple Potato and Dry Pea Flours

Measuring antioxidant activity using a biologically relevant assay adds important evidence to aid in understanding the role of phytochemicals based on data from in vivo and chemical assays of extrusion processed purple potato and pea flours. A cellular antioxidant activity assay could provide biologically relevant information on bioactive compounds in raw as well as processed food products. The objective of this study was to investigate the complete phytochemical profiles, antioxidant activity, cellular antioxidant activity, and their contribution to bioactivity in purple potato flour, dry pea flour, raw formulations, and extrusion cooked products prepared with the above ingredients. The free fraction of extracts contributed 68, 64, and 88% to total phenolics, total antioxidant activity (ORAC value), and total flavonoids, respectively, in purple potato flour (PPF). Similarly, extracts in the free fraction contributed 87, 86, and 64% to total phenolics, total antioxidant activity (ORAC value), and total flavonoids, respectively, in dry pea flour (DPF). The amount of total phenolics and total flavonoids in purple potato flour and the antioxidant activity of PPF and DPF were comparable to published data. However, a higher amount in the total flavonoids and lower in the total phenolics of DPF were observed. Caffeic, p-coumaric, and ferulic acids were mostly observed in the bound extracts of raw formulations as in the extrudates, whereas chlorogenic acid was predominant in the free extracts. The extruded products had significantly higher (p < 0.05) content of total phenolics, ORAC antioxidant activity, and flavonoids, compared to the raw formulations. Extrusion processing increased the cellular antioxidant activity of the extrudates prepared from 35:65 and 50:50 PPF/DPF (w/w) of ingredients compared with control raw formulations in a dose-dependent manner. Increase of PPF significantly increased (p < 0.05) the cellular antioxidant activity of 35-50% PPF formulations.

Effects of buffer additives and thermal processing methods on the solubility of shrimp (Penaeus monodon) proteins and the immunoreactivity of its major allergen

This study examines the potential of two buffer additives (Tween 20 and DTT) to improve the solubility of proteins from shrimp subjected to different heat treatments and the allergenicity of tropomyosin in the extracts. The concentration of soluble proteins extracted by all the buffers from processed shrimp was significantly reduced compared with untreated samples. The concentration of total soluble proteins from heat treated shrimp increased significantly when phosphate buffer containing both surfactant and reducing agent was used as the extraction buffer. However, the concentrations of heat-stable proteins in the buffers were mostly similar. The electrophoretic profile of extracted proteins showed that tropomyosin is very stable under the different heat treatment methods used in this study except for high pressure steaming where the intensity of tropomyosin band was reduced. Competitive inhibition ELISA showed that high pressure steaming reduced the allergenicity of tropomyosin compared with other heat treatments methods.

Shrimp Tropomyosin Retains Antibody Reactivity after Exposure to Acidic Condition

BACKGROUND Although shrimp can be found in certain high acid food matrices, the allergenic capacity of shrimp tropomyosin exposed to low pH condition has not been fully clarified. Thus, a model marinade comprising white vinegar adjusted to different pH was used to determine the effects of acid-induced denaturation on the immunoreactivity of tropomyosin. RESULTS Whole shrimp experienced either swelling or shrinkage after marination depending on the vinegar pH and the final muscle pH. The extractability of soluble myofibrillar proteins was reduced significantly among shrimp marinated in vinegar at pH 1.0-3.5, and a substantial amount of tropomyosin was retained in the insoluble pellets. Consequently, the immunoglobulin E (IgE)-binding capacity of tropomyosin was significantly lower in the soluble protein fraction of shrimp marinated at pH 1.0-3.5 compared with samples marinated at pH 4.8 and control. However, tropomyosin in the insoluble protein fraction of all marinated shrimp showed strong IgE-binding capacity at all marinating conditions. CONCLUSION Thus, tropomyosin in shrimp exposed to low pH condition retained its allergenic capacity owing to the conservation of its linear epitopes. Analysis of the insoluble protein fraction was crucial for the accurate determination of the effect of low pH condition on the immunoreactivity of this allergen.

Effects of Microwave and Ultrasound Assisted Extraction on the Recovery of Soy Proteins for Soy Allergen Detection

The extraction of soy proteins for soy allergen detections is conventionally achieved with PBS buffer for at least 2 h at room temperature or 4 °C. This method has been reported to be inefficient due to time consumption and inadequate protein extraction resulting in false negative allergen detection and mislabeling of foods containing allergenic proteins. This study investigated the application of microwave (MAE) and ultrasound assisted extraction (UAE) techniques to extract and improve recovery of allergens from various soy matrices. Soy proteins were extracted from raw soy flour, soy protein isolate (SPI) and soy milk using MAE at 60, 70, and 100 °C for 5 and 10 min and UAE at 4 and 23 °C for extraction times of 1, 5, and 10 min with PBS, Laemmli and urea buffers. Extracts were analyzed for total proteins, protein profile, and antibody-based detection (ELISA) of soy proteins. Conventional extraction with each of the buffers was used as controls. Overall, proteins recovered from MAE and UAE samples were higher than recoveries from the controls in all soy matrices. Under all extraction conditions, Laemmli and urea buffer recovered more proteins than PBS. Electrophoresis analysis of protein showed bands around 75, 50, and 33 kDa indicating the presence of soy allergenic proteins β-conglycinin and glycinin, in all samples. Using sandwich ELISA, control and UAE extracts resulted in high soy protein detection but this reduced in MAE extracts.

Principles of Food Preservation

Food preservation is an action or method used to maintain foods at certain desirable properties or quality to obtain maximum benefit. A good method of food preservation is one that slows down or prevents altogether the action of the agents of spoilage without damaging the food. To achieve this, certain basic methods are applied depending on the food types. Food preservation has been an essential activity throughout human history. The cycle of seasons brings periods of shortage and abundance of various foods at different times of the year. Preservation makes it possible to consume some of these foods during off seasons, throughout the year. Food preservation usually involves controlling or preventing growth of microrganisms or minimizing the quality degradation due to microbial spoilage or unwanted chemical changes in foods such as rancidity due to oxidation of fats over time. Preservation of foods is no longer simple and straightforward today; it has evolved to a highly inter-disciplinary field of science. In recent years, many new sophisticated preservation techniques have developed to extend the quality and shelf-life, minimize risk, protect the environment, and improve functional, sensory, and nutritional properties. Many of emerging preservation technologies have already reached commercial adoption in specific applications while many others remain promising. Development of suitable equipment, especially for continuous processing for a variety of foods and standardization of the process parameters for easy regulatory approval will pave the way for improved food preservation. The objective of this chapter was to examine the science and technology involved in the manipulation of conventional as well as sophisticated emerging preservation methods.

Potential of colored potatoes for producing high antioxidant snack foods

Potatoes are one of the most important vegetables in the world in terms of consumption and overall nutritional value. This paper aims at determining potential of color fleshed potatoes for producing processed products rich in antioxidants. Antioxidants in peeled purple flesh potatoes was determined to be 332 µg Trolox equivalent per gram of dry weight (µg TE/g DW) followed by 82 µg TE/g DW in red and 79 µg TE/g DW in yellow potatoes. Purple potatoes were also high in phenolics (2914 µg Gallic acid equivalent per gram of dry weight (µg GAE/g DW)) followed by red (944 µg GAE/g DW) and yellow (941 µg GAE/g DW) potatoes. 1.671 mg per gram of dry weight anthocyanins was found in purple potatoes, compared to 0.014 mg/g DW and 0.014 mg/g DW in red and yellow potatoes, respectively. Purple potatoes were peeled, blanched and dehydrated with three different drying methods to prepare potato flakes. Preliminary results showed 100–180 % increase in total antioxidant capacity (TAC) in all the drying methods. Freeze drying increased TAC by 182 % followed by drum drying (140 %) and refractance window drying (103 %). All the selected drying methods showed a two fold increase in total phenolic content (TP). Refractance window drying increased TP by 270 % followed by drum drying (212 %) and freeze drying (207 %). However, 20–40 % losses in total anthocyanins content (TA) were observed in all the three drying methods with 41 and 45 % of losses found in drum drying and freeze drying whereas refractance window drying retained 77 % of TA. Potential of colored potatoes rich in antioxidants should provide excellent opportunities for production of nutritionally enhanced food products.