Total phenolics and antioxidant capacity of heat-treated peanut skins

Effects of dietary supplementation of peanut skins (Arachis hypogaea) on performance, digestibility, and rumen fermentation of cattle: a meta-analysis

This study aimed to estimate the magnitude of the effects of dietary inclusion of peanut skins (PS) byproduct (Arachis hypogea L.) on intake, total-tract digestibility, and rumen fermentation of cattle via meta-analysis. Data were collected following the PRISMA methodology. Nine manuscripts and a graduate thesis met the inclusion criteria from 1983 to 2010. The effect size was estimated by calculating the weighted raw mean differences (RMD) between PS vs. control diets. The RMD was compared with a robust variance estimation method followed by a meta-regression and a dose-response analysis fitting the diet characteristics like crude protein content (CP), NDF content, ether extract content (EE), tannin content, and PS level in diet (0 to 40%) as covariates. Dietary PS decreased (P < 0.01) total-tract CP digestibility (52.0 vs. 64.3%), final body weight (371.5 vs. 397.9 kg), and average daily gain (1.14 vs. 1.44 kg/day) among treatment comparisons. Likewise, PS decreased total VFA (92.6 vs. 107.6 mmol/L) and NH3-N (8.22 vs. 12.1 mg/dL), but no effects were observed on rumen pH (6.47 vs. 6.14) and VFA molar proportions. Despite the between-cluster variance, dietary PS increased the ether extract digestibility (77.5 vs. 70.2%) among treatment comparisons. The subset and dose-response analysis revealed that PS should not exceed 8% (DM basis) in the diet to prevent negative effects on CP digestibility and animal performance. In conclusion, the results of this meta-analysis do not support the dietary inclusion of PS in cattle diets beyond 8%.

Targeted metabolome analysis reveals accumulation of metabolites in testa of four peanut germplasms

Cultivated peanut (Arachis hypogaea L.) is an important source of edible oil and protein. Peanut testa (seed coat) provides protection for seeds and serves as a carrier for diversity metabolites necessary for human health. There is significant diversity available for testa color in peanut germplasms. However, the kinds and type of metabolites in peanut testa has not been comprehensively investigated. In this study, we performed metabolite profiling using UPLC-MS/MS for four peanut germplasm lines with different testa colors, including pink, purple, red, and white. A total of 85 metabolites were identified in four peanuts. Comparative metabolomics analysis identified 78 differentially accumulated metabolites (DAMs). Some metabolites showed significant correlation with other metabolites. For instance, proanthocyanidins were positively correlated with cyanidin 3-O-rutinoside and malvin, and negatively correlated with pelargonidin-3-glucoside. We observed that the total proanthocyanidins are most abundant in pink peanut variety WH10. The red testa accumulated more isoflavones, flavonols and anthocyanidins compared with that in pink testa. These results provided valuable information about differential accumulation of metabolites in testa with different color, which are helpful for further investigation of the molecular mechanism underlying biosynthesis and accumulation of these metabolites in peanut.

An overview on extraction, composition, bioactivity and food applications of peanut phenolics

Peanuts contain a diverse and vast array of phenolic compounds having important biological properties. They are allocated mostly in the seed coat (skin), an industrial waste with minor and undervalued applications. In the last few years, a considerable amount of scientific knowledge about extraction, composition, bioactivities and health benefits of peanut skin phenolics has been generated. The present review was focused on four main aspects: a) extraction methods and technologies for obtaining peanut skin phenolics with an emphasis on green-solvent extraction processes; b) variations in chemical profiles including those due to genetic variability, extraction methodologies and process-related issues; c) bioactive properties, especially antioxidant activities in food and biological systems; d) update of promising food applications. The revision was also aimed at identifying areas where knowledge is insufficient and to set priorities for further research.

Extracts of Peanut Skins as a Source of Bioactive Compounds: Methodology and Applications

Peanut skins are a waste product of the peanut processing industry with little commercial value. They are also significant sources of the polyphenolic compounds that are noted for their bioactivity. The extraction procedures for these compounds range from simple single solvent extracts to sophisticated separation schemes to isolate and identify the large range of compounds present. To take advantage of the bioactivities attributed to the polyphenols present, a range of products both edible and nonedible containing peanut skin extracts have been developed. This review presents the range of studies to date that are dedicated to extracting these compounds from peanut skins and their various applications.

Peanut skin phenolic extract attenuates hyperglycemic responses in vivo and in vitro

Diabetes affects at least 285 million people globally, and this number continues to increase. Clinical complications include impaired glucose metabolism, hyperglycemia, dyslipidemia, atherosclerosis and non-alcoholic fatty liver disease. Evidence has shown that natural phenolics play a protective effect on both the development and management of type 2 diabetes. This study evaluated effects of the extract from peanut skins containing polyphenols on induced- hyperglycemia using in vivo and in vitro methods. A human hepatocellular liver carcinoma cell line (HepG2) was used to investigate the effect of the peanut skin extract on cell viability after exposure to high glucose concentrations. In vivo, the effect of peanut skin extract on an oral glucose tolerance was investigated in human subjects. Fifteen participants aged 21–32 underwent an oral glucose tolerance test with five treatments: 1) 50-gram glucose solution (reference); 2). 50-gram glucose solution, followed by 12 mg of vegi-capsulated maltodextrin; 3) 50-gram glucose solution, followed by 120 mg of vegi-capsulated maltodextrin-encapsulated peanut skin extract; 4). 50-gram glucose solution, followed by 28 grams of unfortified coated peanuts; 5) 50-gram glucose solution, followed by 28 grams of chili lime coated peanuts fortified with encapsulated peanut skin extract. Glucose levels were measured using a continuous monitor. Peanut skin extract was found to attenuate the decrease in cell viability in high glucose treated HepG2 cells, showing a protective effect against hyperglycemia induced cell death. No difference in the glycemic response area under the curve between any treatments using the tolerance test, but the treatment of the peanut skin extract with the glucose reference resulted in a significantly lower peak blood glucose response at 45 minutes, indicating that it was effective at reducing the glycemic response. The present study shows that the phenolic extract of peanut skins has an antidiabetic effect, further confirming their value as a functional food ingredient.

Acceptability of Peanut Skins as a Natural Antioxidant in Flavored Coated Peanuts

Peanut skins are a low-value byproduct of the peanut processing industry. Following their removal during the preparation of common peanut products, they are either discarded or used as a minor component of animal feed. Studies have found peanuts skins to be rich in health promoting phenolic compounds and thus have potential as a functional food ingredient. The aim of this study was to evaluate a new product that included the encapsulated phenolic extract from peanut skins in a flavored coating for peanuts. The phenolic compounds were extracted from peanut skins and then encapsulated in 10.5% (w/w) maltodextrin in to reduce the bitter flavor. The encapsulated phenolic extract was added at varying concentrations to honey roast flavored and chili lime flavored coatings which were applied to roasted peanuts. The resulting total phenolic content and antioxidant potential of the coated peanuts were evaluated by the Folin-Ciocalteu, DPPH, and β-carotene bleaching assays. A best estimate sensory threshold for the peanut skin extract in the honey roasted and chili lime coating was found to be 12.8% (w/w) and 16.6% (w/w), respectively. The total phenolic content and antioxidant capacity for both the honey roasted and chili lime coated peanuts at their threshold was found to be significantly higher than control peanuts that did not contain peanut skins in the coating. The increased antioxidant activity and unaltered flavor profile at the sensory threshold levels of peanut skins demonstrated their potential as a functional food ingredient.

PRACTICAL APPLICATION

The ability of polyphenols to act as antioxidants suggests that extracts of peanut skins containing polyphenols can be used as functional ingredients in new food products. The encapsulation of peanut skin extract in maltodextrin allowed for the incorporation of the extracts into flavored coatings for peanuts at levels high enough to increase the antioxidant activity without impacting sensory profiles. Utilization of this by-product of the peanut can create an economic opportunity for the peanut industry.

Phenolic Profiles and Antioxidant Activity of Germinated Legumes

Bioactive compounds, which are naturally produced in plants, have been concerned with the food and pharmaceutical industries because of the pharmacological effects on humans. In this study, the individual phenolics of six legumes during germination and antioxidant capacity from sprout extracts were determined. It was found that the phenolic content significantly increased during germination in all legumes. Peanuts showed the strongest antioxidant capacity in both the DPPH• (1,1-diphenyl-2-picrylhydrazyl) method and the reducing power assay (32.51% and 84.48%, respectively). A total of 13 phenolic acids were detected and quantified. There were 11 phenolic constituents identified in adzuki beans; 10 in soybeans; 9 in black beans, mung beans, and white cowpeas; and 7 compounds in peanuts. Sinapic acid and cinnamic acid were detected in all six legume sprouts, and their quantities in germinated peanuts were the highest (247.9 µg·g⁻¹ and 62.9 µg·g⁻¹, respectively). The study reveals that, among the investigated legumes, germinated peanuts and soybeans obtained maximum phenolics and antioxidant capacity.

Bioassay-guided isolation of proanthocyanidins with antioxidant activity from peanut (Arachis hypogaea) skin by combination of chromatography techniques

Purification and bioassay-guided fractionation were employed to isolate proanthocyanidins with antioxidant activity from peanut skin (Arachis hypogaea Runner 886). The crude extract was prepared with acetone (60% v/v) and purified using chromatographic methods, including a semipreparative HPLC technique. As a result, two proanthocyanidins were isolated and identified using NMR, epicatechin-(2 β → O → 7, 4 β → 8)-catechin (proanthocyanidin A1) and epicatechin-(β → 2 O → 7, 4 β → 8)-epicatechin (proanthocyanidin A2). Despite the structural similarity, differences were observed in their antioxidant activity. Proanthocyanidin A1 proved to be more active, with EC50 value for DPPH radical scavenging of 18.25 μg/mL and reduction of Fe(3+)-TPTZ complex of 7.59 mmol/g, higher than that of synthetic antioxidant BHT. This compound evaluated by ABTS(+) was similar to that of natural quercetin. Therefore, peanut skin is an important source of bioactive compounds that may be used as a mild antioxidant for food preservation.

Functional analysis of unfermented and fermented citrus peels and physical properties of citrus peel-added doughs for bread making

Several studies have indicated citrus peels (CP) contain specific methoxy flavones, e.g. nobiletin and tangeretin, which have been shown to prevent numerous diseases. However, research reports regarding their application as food additive in healthy baked products is scarce. In our study, both unfermented (UF) and fermented (F) citrus peels were processed under different dry hot-air temperatures to make four citrus peel powders , UF-100 °C,UF-150 °C, F-100 °C, F-150 °C, respectively. The analysis of the basic components and nutraceuticals as well as antioxidant activity were conducted. Various percentages of CP were added to dough and toast bread for physical property and sensory evaluations. The results indicated the contents of crude proteins (3.3-4.3 mg/g) and fibers (10.9-14.9 %) among the four samples were similar. The UF extracts showed better antioxidant activities than F extracts. HPLC analysis indicated the contents of hesperidine, nobiletin and tangeretin in CP extracts were UF-150 °C > UF-100 °C. Farinograph analysis indicated a linear relation between CP powder content and the parameters of the physical properties of dough. A high percentage of fibrous CP powder in dough increases the water adsorption capacity of the dough, resulting in a decrease in its stability The sensory evaluation results indicated a greater acceptability of UF-added toast bread relative to the F-added one. Among these, according to the statistical anaylsis, the UF-150 °C 4 % and UF-100 °C 6 % groups were the best and F-150 °C 2 % group was the poorest in overall acceptability.

Total antioxidant capacity, total phenolic content and mineral elements in the fruit peel of Myrciaria cauliflora

The in vitro antioxidant capacity, total phenolic content and mineral elements of the fruit peel of Myrciaria cauliflora were investigated. The antioxidant capacity was analyzed by the diphenylpicrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP) and β-carotene methods. The assays based on the DPPH (EC50 = 3.18 g sample/g DPPH), ABTS•+ (1017 μmol Trolox/g sample), FRAP (1676 µM Fe2SO4/g sample) and β-carotene/linoleic acid (70% of oxidation inhibition) methods indicated a high antioxidant capacity of the fruit peel extract of the plant. The Folin-Denis method was more efficient in determining the total phenolic compound contents in the different solvents than the Folin-Ciocalteu one. Extractions made with 4:1 methanol-water, 4:1 ethanol-water, 3:2 ethanol-water and 3:2 acetone-water solutions using the Folin-Denis method exhibited high contents of phenolic compounds (18.95, 14.06, 12.93 and 11.99 mg GAE/g, respectively). Potassium was the major element found in the fruit peel, followed by phosphorus, calcium, magnesium and iron, in that order. As a result, the fruit peel of M. cauliflora can be considered as an important source of natural antioxidants and essential elements of easy access for the population and for application in the food industry.

Peanut skins-fortified peanut butters: effect of processing on the phenolics content, fibre content and antioxidant activity

Incorporation of ground peanut skins (PS) into peanut butter at 1.25%, 2.5%, 3.75%, and 5.0% (w/w) resulted in a marked concentration-dependent increase in both the total phenolics content (TPC) and antioxidant activity. Using dry-blanched PS to illustrate, the TPC increased by 86%, 357%, 533%, and 714%, respectively, compared to the peanut butter control devoid of PS; the total proanthocyanidins content (TPACs) rose by 633%, 1933%, 3500%, and 5033%, respectively. NP-HPLC detection confirmed that the increase in the phenolics content was attributed to the endogenous proanthocyanidins of the PS, which were characterised as dimers to nonamers by NP-HPLC/ESI-MS. FRAP values increased correspondingly by 62%, 387%, 747%, and 829%, while H-ORAC(FL) values grew by 53%, 247%, 382%, and 415%, respectively. The dietary fibre content of dry-blanched PS was ~55%, with 89-93% being insoluble fibre. Data revealed that PS addition enhances the antioxidant capacity of the peanut butter, permits a "good source of fibre" claim, and offers diversification in the market's product line.

Behavior of Escherichia coli O157:H7 on damaged leaves of spinach, lettuce, cilantro, and parsley stored at abusive temperatures

Recent foodborne illness outbreaks associated with the consumption of leafy green produce indicates a need for additional information on the behavior of pathogenic bacteria on these products. Previous research indicates that pathogen growth and survival is enhanced by leaf damage. The objective of this study was to compare the behavior of Escherichia coli O157:H7 on damaged leaves of baby Romaine lettuce, spinach, cilantro, and parsley stored at three abusive temperatures (8, 12, and 15 degrees C). The damaged portions of leaves were inoculated with approximately 10(5) CFU E. coli O157:H7 per leaf. The pathogen grew on damaged spinach leaves held for 3 days at 8 and 12 degrees C (P < 0.05), with the population increasing by 1.18 and 2.08 log CFU per leaf, respectively. E. coli O157:H7 did not grow on damaged Romaine leaves at 8 or 12 degrees C, but growth was observed after 8 h of storage at 15 degrees C, with an increase of less than 1.0 log. Growth of E. coli O157:H7 on Romaine lettuce held at 8 or 12 degrees C was enhanced when inocula were suspended in 0.05% ascorbic acid, indicating the possibility of inhibition by oxidation reactions associated with tissue damage. Damaged cilantro and Italian parsley leaves held at 8 degrees C for 4 days did not support the growth of E. coli O157:H7. Behavior of the pathogen in leaf extracts differed from behavior on the damaged tissue. This study provides evidence that the damaged portion of a leafy green is a distinct growth niche that elicits different microbial responses in the various types of leafy greens.