Environmentally Friendly Approach to Pectin Extraction from Grapefruit Peel: Microwave-Assisted High-Pressure CO2/H2O.

In this research, pectin extraction from grapefruit peel (GPP) was performed using a microwave-assisted high-pressure CO2/H2O (MW-HPCO2) system. The Box-Behnken design of response surface methodology was applied for the optimization of MW-HPCO2 extraction conditions to obtain the highest pectin yield. The effects of temperature, time, and liquid/solid ratio on pectin yield were examined in the range of 100-150 °C, 5-15 min, and 10-20 mL g-1, respectively. Under the optimum extraction conditions (147 °C, 3 min, and 10 mL g-1), pectin was obtained with a yield of 27.53%. The results obtained showed that the extraction temperature and time had a strong effect on the pectin yield, while the effect of the liquid/solid ratio was not significant, and the pectin was effectively extracted from grapefruit peel (GP) using MW-HPCO2. Additionally, the application of GPP in apricot jam showed that MW-HPCO2-GPP can be used as a thickener in the food industry. The yield and physicochemical properties (ash, protein, galacturonic acid, reducing sugar and methoxyl content, degree of esterification, equivalent weight, color, viscosity) of pectin extracted in the optimum conditions of the MW-HPCO2 method were superior to pectin extracted by the traditional method. The results of this study revealed that MW-HPCO2 could be an innovative green and rapid technique for pectin extraction.

Hot air-assisted radio frequency drying of grated potato (Solanum tuberosum L.): Drying behavior and the associated effect on characteristics of potato flour.

In this study, drying of grated potato in a hot air-assisted radio frequency system (HA-RF) and the associated effects on the final potato flour quality were studied. The drying behavior of the grated potatoes at different electrode distances (70-90 mm) and sample thickness (2-4 cm) was investigated. The safe drying (without burning tendency) of the maximum amount of sample (1000 g) in a reasonable drying time was carried out at 80 mm of electrode gap and 4 cm of sample thickness. HA-RF drying kinetics were studied and compared with hot air (HA) and radio frequency (RF) (without hot air) drying methods. HA-RF drying increased drying rate and shortened drying time by about 58% and 70% compared to HA and RF drying, respectively. The properties of the final potato flour obtained after HA-RF drying were also compared with those produced by RF, HA, and freeze drying. The flour obtained by HA-RF was superior to RF and HA dried samples with better retention of cellular microstructure and color. The drying method significantly affected the functional properties, thermal characteristics, pasting properties, and other characteristics of potato flours. PRACTICAL APPLICATION: HA-RF as an alternative drying technology was used for the first time to produce potato flour. The functional, thermal, and structural properties of the HA-RF dried product were compared with those dried by HA, RF, and freeze drying. The results of this study ensured very useful information for the use of potato flour obtained by different drying methods in the development of products with specific functional and rheological properties.

Effect of sequential-combined solar energy assisted hot air and hot air assisted radio frequency drying on the physical and chemical properties of dried apricots.

Quality characteristics of sulphured and non-sulphured apricots dried with a sequential combined pilot scale solar assisted hot air and hot air assisted radio frequency dryer and conventional sun system were compared. The combined drying approach showed improved color, hardness, antioxidant activity and retention of vitamin C, ß-carotene and total phenolic content values compared to conventional sun drying both for sulphured and non-sulphured samples. The effects of sulphur concentration and addition of pistachio hull extract as a treatment prior to drying were also investigated. Increase in sulphur concentration and addition of extract resulted in considerable quality (with respect to color, Vitamin C, ß-carotene and total phenolic content) increase in apricots. The apricots pretreated with extract had the highest total phenolic content and antioxidant activity. This study demonstrated that combined drying process is an effective drying method for apricots with the better preservation of product quality attributes.

Statistical investigation of the bioprocess conditions of alkali combined twin-screw extrusion pretreatment to enhance fractionation and enzymatic hydrolysis of bulgur bran.

BACKGROUND: Bulgur bran (BB) is a potential source for the production of value-added products such as fermentable sugars and xylooligosaccharides (XOs). In this study, alkali combined twin-screw extrusion pretreatment was performed and statistically optimized to enhance fractionation and enzymatic hydrolysis of BB. The pretreatment conditions (barrel temperature, screw speed and alkali impregnation) were optimized by Box-Behnken design (BBD) to obtain the highest hemicellulose separation from BB. The obtained fractions were analyzed for the production of fermentable sugars and XOs. RESULTS: The results revealed that twin-screw extrusion of BB performed at 67 °C barrel temperature and 250 rpm screw speed after alkali impregnation at 0.02 g alkali g-1 biomass concentration provided 40.4% higher hemicellulose separation yield compared to the untreated BB. Alkali combined twin-screw extrusion pretreatment increased the enzymatic hydrolysis yield of BB fourfold, whereas a 13-fold increase was achieved after the separation of hemicellulose from pretreated BB. Xylose (X1)-free xylobiose (X2) was the main product after xylanase hydrolysis of hemicellulose fraction. SEM images confirmed the morphological modifications in BB, which were in agreement with the enhanced fractionation performance and the higher enzymatic hydrolysis yield. CONCLUSION: The results of this study suggested that pretreatment by alkali combined twin-screw extrusion followed by alkali extraction could be a reliable and effective process for fractionation of BB and production of fermentable sugars and XOs. © 2022 Society of Chemical Industry.

Hot air-assisted radio frequency drying of apricots: Mathematical modeling study for process design.

Conventional hot air and solar energy processes have been used for apricot. These processes had adverse effects on the quality due to the longer process times, and this indicates the need for an innovative approach. Radio frequency (RF) processing has innovation potential for drying with its volumetric heating feature, but an optimal process should be designed for process efficiency in industrial-scale applications. Therefore, the objective of this study was to confirm the RF process for industrial-scale apricot drying. For this purpose, a mathematical model was developed to predict temperature and moisture content change of apricots during drying, and experimental validation study was carried out. For the RF drying process, pre-dried apricots (0.58-0.75 kg water/kg dry matter, db) by solar energy were used. The purpose was to start the RF process at a suitable moisture content level as this process was not feasible to apply directly due to the high initial moisture content of apricots (up to 4 kg water/kg dry matter, db). RF drying experiments were carried out in a 10 kW hot air-assisted (50-60°C) staggered through electrode system. Optimum electrode gap was 81 mm with 2500 V potential of the charged electrode. Final moisture content of the dried apricots was 0.25-0.33 kg water/kg dry matter (db). Following the model validation for temperature and moisture content change, industrial-scale apricot drying scenarios were demonstrated to confirm the RF process for feasibility and process design. PRACTICAL APPLICATION: A comprehensive mathematical model was developed for radio frequency (RF) drying of apricots. This model was experimentally validated with respect to the temperature and moisture content change. Various process design studies were carried out for an industrial-scale apricot drying process to confirm the process feasibility. With this background, the results of this study can be directly used in an industrial drying for an optimal process design and energy efficiency.