Tannins are groups of phenolic compounds that cause astringency and turbidity in fruit juices. Many factors had an influence on the concentration of tannins in fruit juices, including cultivar, parts and maturity stages, as well as pH and viscosity of juices. Many methods were investigated for tannins removal from fruit juices. Physical methods included heat treatment and membrane filtration. Chemical methods were based on clarifying agents included polysaccharides (starch and chitosan), proteins (gelatin and casein) and synthetic polymers (polyvinyl polypyrolidone). The enzymatic method was based on the application of enzyme tannase to hydrolyze tannins into soluble compounds. Tannins removal efficiency of each method depended on fruit juice, type and parameters of the method. Downstream process should be considered especially for application of clarifying agents.
Cashew apple, the peduncle of cashew fruit, is an agricultural waste byproduct from harvesting cashew nuts. Cashew apple juice contains about 10% reducing sugar. Its bagasse contains about 20% of cellulose. The byproducts can be used as a substrate for several microbial fermentation processes. Wine and bioethanol were produced by Saccharomyces cerevisiae. Probiotic beverage and lactic acid were produced by Lactobacillus casei. Biosurfactants-rhamnolipids, emulsan and surfactin were synthesized by Pseudomonas aeruginosa, Acinetobacter calcoaceticus and Bacillus subtilis, respectively. Tannase and pectinase were produced during solid-state fermentation of Aspergillus spp. Prebiotic oligosaccharides were synthesized by the activity of dextransucrase produced by Leuconostoc spp. Cashew apple is a potential substrate for producing a variety of products, depending on the type of microorganisms used.
Thai eat the young leaves of mango as vegetables. Antioxidants in young leaves of mango cultivars 'Talapnak', 'Chok Anan' and 'Nam Dok Mai' were identified by high-performance liquid chromatography coupled with an online ABTS assay (HPLC-ABTS) and electrospray ionization mass spectrometer (HPLC-ESI-MS). Young leaves of mango cv. 'Nam Dok Mai' had the highest antioxidant capacity. Major antioxidants in young mango leaves were mangiferin and benzophenones (maclurin and iriflophenone derivatives). Mangiferin presented in higher quantities than other compounds in each cultivar, with cv. 'Talapnak ' containing the most (37.92±0.98 mg/g DW) . The compound with the highest antioxidant capacity in all cultivars was mangiferin pentoside (from 1.19±0.25 mmol TE/g DW in cv. 'Chok Anan' to 2.13±0.04 mmol TE/g DW in cv. 'Talapnak'). The compound with the highest Trolox equivalent antioxidant capacity was maclurin galloyl glucoside (1.75±0.62 mol TE/mol).
The juice extracted from cashew apples contains tannins that must be reduced due to their astringency and anti-nutritional properties. This study investigated reducing the tannins in cashew apple juice by mixing gelatin at 0.0 to 1.0% (w/v) with the juice for 5 to 15 min. Response surface methodology was used to simulate tannin concentration, turbidity, and weight of precipitate as a function of gelatin concentration and mixing time. All models were significant (P<0.01) and residuals exhibited normal distribution. Increasing the gelatin concentration decreased tannins and juice turbidity. Optimal conditions for minimum concentration of tannins and turbidity were obtained by adding gelatin at 0.67% (w/v) for 15 min. Cashew apple juice with the tannins reduced could be used in the subsequent production of wine and bioethanol.
Green soybean (Glycine max L.) pods (GSP) are agro-industrial waste from the production of frozen green soybean and milk. These pods contain natural antioxidants and various bioactive compounds that are still underutilized. Polyphenols and flavonoids in GSP were extracted by ultrasound technique and used in the antioxidant fortification of green soybean milk. The ultrasound extraction that yielded the highest total polyphenol content and antioxidant activities was 50% amplitude for 10 min. Response surface methodology was applied to analyze an optimum ultrasonic-assisted extraction (UAE) condition of these variables. The highest desirability was found to be 50% amplitude with an extraction time of 10.5 min. Under these conditions, the experimental total phenolic content, total flavonoid content, and antioxidant activity were well matched with the predicted values (R2 > 0.70). Fortification of the GSP extracts (1–3% v/v) in green soybean milk resulted in higher levels of bioactive compounds and antioxidant activity in a dose-dependent manner. Procyanidins were found to be the main polyphenols in dried GSP crude extracts, which were present at a concentration of 0.72 ± 0.01 mg/100 g. The addition of GSP extracts obtained by using an ultrasound technique to green soybean milk increased its bioactive compound content, especially procyanidins, as well as its antioxidant activity.
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