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Flaxseed gum (FSG) is a heteropolysaccharide consist of neutral and acidic components that makes up approximately 8% of seed mass. FSG was extracted from mixture of brown and golden varieties of flaxseeds by hot water extraction method. The molecular weight distribution, monosaccharide analysis, chemical composition, and surface morphology of FSG were scrutinized in the current study to get a better insight regarding this important polysaccharide. The average molecular weight was recorded as 1,322 kDa with a polydispersity ratio of 1.6 for Mw/Mn and 2.4 for Mn/Mz. High-performance liquid chromatography (HPLC) screening revealed that extracted FSG was comprised of rhamnose, arabinose, mannose, glucose, fucose, xylose, galactose, glucosamine, glucuronic acid, and galacturonic acid, of which mannose and glucosamine have not been reported previously. The antioxidant activities of FSG measured as DPPH, ABTS, reducing power, and total antioxidant activity clearly demonstrated the antioxidant potency of FSG. Fourier-transform infrared spectroscopy (FTIR) and the Nuclear magnetic resonance (NMR) (1 H, 13 C) s pectra ratified the presence of functional groups typical for polysaccharide. PRACTICAL APPLICATIONS: Flaxseed gum is a natural carbohydrate polymar. This study provides useful information regarding antioxidant potential, chemical, and structural characterization of FSG. The availability of a gum is fully characterized with bioactive composition, structural features, and antioxidant potential provides a toolset for the practical application in the food or drug industry.

Fresh and half-dried fruits of lychee (Litchi Chinensis) and longan (Dimocarpus longan) were processed by air drying and implemented in diverse forms as fillings in order to produce chocolate pralines. Both dried fruits and chocolate pralines were characterized with total polyphenols, proanthocyanidins, flavan-3-ols and antioxidant capacity (2, 2-diphenyl-1-picrylhydrazyl, 2, 2-Azino-Bis-3-Ethylbenzothiazoline-6-Sulfonic acid) were determined by spectrophotometric and sensory analyses by quantitative descriptive analysis. Specific polyphenolic compounds were quantified using high-performance liquid chromatography coupled with photodiode array detector. The bioactive content and profile of chocolate pralines produced with the addition of longan and lychee were not significantly altered when compared to plain chocolate, but the sensory analysis revealed a preference for lychee-containing pralines, due to characteristic fruity sensory properties. Since longan and lychee fruits are still underutilized as raw materials and ingredients in food production, preservation by drying and incorporation into new products may enable their popularization and increase functional food production. PRACTICAL APPLICATIONS: Since both longan and lychee are still underutilized as raw materials and ingredients in food production, preservation by drying and incorporation into new products may enable their popularization and increase functional food production.

The study aims to determine drying of sweet potatoes using multifrequency ultrasound (US) pretreatments (20, 40, and 60 kHz) at three different infrared (IR) drying temperatures (60, 70, and 80°C) and evaluate the phytochemical and textural quality of the dried product. Drying time was significantly decreased in moderate US frequency (40 kHz) at 70°C with the increasing drying temperature. Comparing to the fresh samples, the dried samples showed the highest amount of phytochemical contents. The antioxidant activity of the samples increased especially at 60 kHz and 80°C, while US-IR treatments shown a positive impact on total carotenoids contents and β-carotene. For phenolic compounds, Ellagic acid and Rutin were quantified in higher amount while Quercetin-3-rhamnoside and Quercetin 3-β-D-glucoside were two new compounds identified for the first time in sweet potatoes. FTIR spectra showed the successful synthesis of OH group and phenolics in samples treated with the US at 20 kHz. PRACTICAL APPLICATIONS: This study investigated the effects of multifrequency ultrasound with different infrared drying temperatures. The study provides evidence that infrared drying application in synergy with ultrasonic pretreatments can improve drying efficiency and food quality much better than using each method alone. Total phenolic contents and total flavonoid contents remained stable at US 40 kHz and 60°C conditions. The findings showed that moderate ultrasound frequency (40 kHz) at 60°C improved phytochemical properties while antioxidant activities showed better preservation response at 80°C with 60 kHz. In addition, the samples treated with the same US treatment at 40 kHz showed less cell breakage in SEM analysis.