Acid Inhibition on Polyphenol Oxidase and Peroxidase in Processing of Anthocyanin-Rich Juice and Co-product Recovery from Purple-Fleshed Sweetpotatoes.

With high phytochemical and starch contents, purple-fleshed sweetpotatoes (PFSP) have been processed into various functional ingredients and food products including juices and natural colorants. For juice processing, PFSP are usually subjected to heat treatment for inactivation of pigment-degrading enzymes. However, heating of sweetpotatoes gelatinizes starch and produces thick slurry with cooked flavor, which are the drawbacks. Development of alternative processes to overcome the stated problems will be beneficial to sweetpotato processors. This study demonstrated that acidified water (≥3% w/v citric acid) was effective in inhibiting polyphenol oxidase and peroxidase in raw PFSP resulting in an attractive reddish juice. About 93% total phenolics (TP) and 83% total monomeric anthocyanins (TMA) in PFSP were extracted by two repeated extractions. The combined PFSP juice (3.2 L/kg PFSP) had high levels of TP (1,850 mg/L) and TMA (475 mg/L). With the developed process, 167 g dried starch, and 140 g dried high-fiber pomace were obtained for each kg raw PFSP, besides the highly pigmented juice. Pasteurization of the PFSP juice samples (pH 3.2) at 80 °C for 12 s resulted in 15% loss in TMA and had no effect on TP. The results indicated an efficient process to produce sweetpotato juice with high bioactive compounds and recovery of starch and high dietary fiber pomace as co-products. PRACTICAL APPLICATION: Purple-fleshed sweetpotatoes (PFSP) are rich in polyphenolics and antioxidant activities. In PFSP juice extraction, heat treatment to inactivate the pigment-degrading enzymes results in starch gelatinization and cooked flavor. A nonthermal process using acidified water was developed for producing anthocyanin-rich juice from PFSP and concurrently recovering native starch and dried pomace, which would increase the economic feasibility of the developed process. The results demonstrate an efficient process for the sweetpotato industry in producing PFSP pigmented juice and co-products for various food applications.

Cocoa and Whey Protein Differentially Affect Markers of Lipid and Glucose Metabolism and Satiety.

Food formulation with bioactive ingredients is a potential strategy to promote satiety and weight management. Whey proteins are high in leucine and are shown to decrease hunger ratings and increase satiety hormone levels; cocoa polyphenolics moderate glucose levels and slow digestion. This study examined the effects of cocoa and whey proteins on lipid and glucose metabolism and satiety in vitro and in a clinical trial. In vitro, 3T3-L1 preadipocytes were treated with 0.5-100 µg/mL cocoa polyphenolic extract (CPE) and/or 1-15 mM leucine (Leu) and assayed for lipid accumulation and leptin production. In vivo, a 6-week clinical trial consisted of nine panelists (age: 22.6 ± 1.7; BMI: 22.3 ± 2.1) consuming chocolate-protein beverages once per week, including placebo, whey protein isolate (WPI), low polyphenolic cocoa (LP), high polyphenolic cocoa (HP), LP-WPI, and HP-WPI. Measurements included blood glucose and adiponectin levels, and hunger ratings at baseline and 0.5-4.0 h following beverage consumption. At levels of 50 and 100 µg/mL, CPE significantly inhibited preadipocyte lipid accumulation by 35% and 50%, respectively, and by 22% and 36% when combined with 15 mM Leu. Leu treatment increased adipocyte leptin production by 26-37%. In the clinical trial, all beverages significantly moderated blood glucose levels 30 min postconsumption. WPI beverages elicited lowest peak glucose levels and HP levels were significantly lower than LP. The WPI and HP beverage treatments significantly increased adiponectin levels, but elicited no significant changes in hunger ratings. These trends suggest that combinations of WPI and cocoa polyphenols may improve markers of metabolic syndrome and satiety.

Pomegranate as a functional food and nutraceutical source.

Pomegranate, a fruit native to the Middle East, has gained widespread popularity as a functional food and nutraceutical source. The health effects of the whole fruit, as well as its juices and extracts, have been studied in relation to a variety of chronic diseases. Promising results against cardiovascular disease, diabetes, and prostate cancer have been reported from human clinical trials. The in vitro antioxidant activity of pomegranate has been attributed to its high polyphenolic content, specifically punicalagins, punicalins, gallagic acid, and ellagic acid. These compounds are metabolized during digestion to ellagic acid and urolithins, suggesting that the bioactive compounds that provide in vivo antioxidant activity may not be the same as those present in the whole food. Anthocyanins and the unique fatty acid profile of the seed oil may also play a role in pomegranate's health effects. A more complete characterization of pomegranate components and their physiological fate may provide mechanistic insight into the potential health benefits observed in clinical trials.