Antioxidant, Bacteriostatic and Preservative Effects of Extractable Condensed Tannins Isolated from Longan Pericarps and Seeds

Condensed tannins from the pulp of Chinese hawthorn as an anti-browning agent: Structure, activity, and structure-activity relationship

Condensed tannins (proanthocyanidins) were isolated from the pulp of Chinese hawthorn (Crataegus pinnatifida Bge. var. major N.E.Br.) and fractioned into three subfractions (F1-F3) using 40 %, 60 %, and 80 % ethanol on a macroporous resin column. HPLC-ESI-MS analysis revealed that epicatechin-polymerized procyanidins were the predominant components of the three subfractions, with mean degrees of polymerization (mDP) of 5.78, 10.09, and 3.03, respectively. These subfractions exhibited excellent antioxidant capacity and showed a significant positive correlation (P < 0.05) with mDP. The subfraction F2 was further proven to be an efficient inhibitor of polyphenol oxidase (PPO) and bacteria. In addition, subfraction F2 controlled the browning of fresh-cut apples by regulating phenolic metabolism, enhancing antioxidant system, and reducing lipid peroxidation. Overall, these findings provided a theoretical foundation for utilizing condensed tannins from Chinese hawthorn pulp as an effective anti-browning agent for fruits and vegetables.

Preservative effects and mechanism of condensed tannins from Cercis chinensis Bunge leaves on fresh-cut lotus root

This study aimed to investigate the potential of condensed tannins isolated from Cercis chinensis Bunge leaves as natural preservatives for fruits and vegetables. The research demonstrated that C. chinensis leaves condensed tannins (CLCT) significantly delay the browning process and reduce nutritional loss in fresh-cut lotus roots. Prodelphinidins were identified as the primary component of CLCT through electrospray ionization mass spectrometry and high-performance liquid chromatography analyses, with minor proportions of procyanidins and high levels of galloylation. The structural units predominantly consisted of (epi)gallocatechin. CLCT exhibited substantial inhibitory activity against tyrosinase, which may involve interactions with copper ions at the enzyme's active site and alterations in enzyme conformation, resulting in reversible inhibition. Additionally, CLCT displayed remarkable antioxidant and antibacterial properties, effectively scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'- azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radicals and significantly inhibiting the growth of Pseudomonas aeruginosa and Staphylococcus aureus. Overall, the potential of CLCT as a natural preservative and tyrosinase inhibitor underscores its promising application in preserving fruits and vegetables.

Performance of Biodegradable Active Packaging in the Preservation of Fresh-Cut Fruits: A Systematic Review

Fresh-cutting fruits is a common practice in markets and households, but their short shelf life is a challenge. Active packaging is a prominent strategy for extending food shelf life. A systematic review was conducted following the PRISMA guidelines to explore the performance and materials used in biodegradable active packaging for fresh-cut fruits. Sixteen studies were included from a search performed in July 2024 on Scopus and Web of Science databases. Only research articles in English on biodegradable active films tested on cut fruits were selected. Polysaccharides were the most employed polymer in film matrices (87.5%). Antioxidant and anti-browning activities were the active film properties that were most developed (62.5%), while plant extracts and essential oils were the most employed active agents (56.3%), and fresh-cut apples were the most commonly tested fruit (56.3%). Appropriate antioxidant, antibacterial, and barrier properties for fresh-cut fruit packaging were determined. Furthermore, there is a wide range of experimental designs to evaluate shelf-life improvements. In each case, shelf life was successfully extended. The findings show that different storage conditions, fruits, and material configurations can lead to different shelf-life extension performances. Thus, biodegradable active packaging for fresh-cut fruits has a strong potential for growth in innovative, sustainable, and functional ways.

Tannin-Tolerant Saccharomyces cerevisiae Isolated from Traditional Fermented Tea Leaf (Miang) and Application in Fruit Wine Fermentation Using Longan Juice Mixed with Seed Extract as Substrate

This study focused on isolating tannin-tolerant yeasts from Miang, a fermented tea leaf product collected from northern Laos PDR, and investigating related food applications. From 43 Miang samples, six yeast isolates capable of ethanol production were obtained, with five isolates showing growth on YPD agar containing 4% (w/v) tannic acid. Molecular identification revealed three isolates as Saccharomyces cerevisiae (B5-1, B5-2, and C6-3), along with Candida tropicalis and Kazachstania humilis. Due to safety considerations, only Saccharomyces spp. were selected for further tannic acid tolerance study to advance food applications. Tannic acid at 1% (w/v) significantly influenced ethanol fermentation in all S. cerevisiae isolates. Notably, B5-2 and C6-3 showed high ethanol fermentation efficiency (2.5% w/v), while others were strongly inhibited. The application of tannin-tolerant yeasts in longan fruit wine (LFW) fermentation with longan seed extract (LSE) supplementation as a source of tannin revealed that C6-3 had the best efficacy for LFW fermentation. C6-3 showed promising efficacy, particularly with LSE supplementation, enhancing phenolic compounds, antioxidant activity, and inhibiting α-glucosidase activity, indicating potential antidiabetic properties. These findings underscore the potential of tannin-tolerant S. cerevisiae C6-3 for fermenting beverages from tannin-rich substrates like LSE, with implications for functional foods and nutraceuticals promoting health benefits.

Inhibitory effects of longan seed extract on polycyclic aromatic hydrocarbons formation and muscle oxidation in baked mutton kebabs

Longan seeds, rich in phenolic compounds with antioxidant properties, are an underestimated by-product of longan processing. Polycyclic aromatic hydrocarbons (PAHs), which are carcinogenic and mutagenic, are produced during the cooking of meat products at high temperatures. The effects of different concentrations of longan seed extract (LSE, 0.2, 0.6, 1.0 mg/mL) on the formation of PAHs and muscle oxidation in mutton kebabs were investigated. Mutton kebabs were baked at 150, 200, 250 °C for 20 min, respectively, and the contents of PAHs, the degree of lipid and protein oxidation were evaluated. The results showed that LSE exhibited positive effects in inhibiting total PAHs formation (range from 14.9 to 48.8 %), decreasing the thiobarbituric acid reactive substances (TBARS) values (range from 17.1 to 39.1 %), reducing carbonyl content (range from 22.0 to 51.2 %) and increasing sulfhydryl content (range from 18.6 to 51.8 %). This study provided a guidance and potential solution for reducing the content of PAHs and muscle oxidation levels in baked meat.

Phytochemical Statistical Mapping of Red Grape Varieties Cultivated in Romanian Organic and Conventional Vineyards

Red grapes are rich in phytochemicals such as phenolics and flavonoids, which are strongly correlated with their antioxidant activity. Thus, grapes as-harvested and grape extracts, especially those obtained from their seeds and pulp, have been reported to have health benefits, and accordingly, grapes and their derivatives are considered potential functional food ingredients. The total phenolic content, total flavonoid content, and the antioxidant activity of skin, pulp, and seeds of four grape varieties grown both in conventional and organic vineyards were examined in this study. Phytochemical characteristics of one native Romanian variety, Feteasca Neagra, were compared with data measured for three red grape varieties more commonly cultivated worldwide (Merlot, Pinot Noir, and Muscat Hamburg). It was found that the seeds of the Pinot Noir variety grown in an organic system contained the highest total phenolics of 169.53 ± 7.32 mg gallic acid equivalents/g and the highest total flavonoid content of 388.25 ± 10.72 mg quercetin equivalents/g, values corresponding to high antioxidant activity (312.84 ± 12.81 mg ascorbic acid equivalents/g). The total flavonoid content in the hydroalcoholic extracts obtained from seeds of Pinot Noir (organic vineyard) was around 24.5-fold higher than that of the skin of Pinot Noir (conventional vineyard). Experiments showed that seeds of all four tested grape varieties are good sources of total flavonoids, not only of total phenolics. When referring to the organic vineyard, the skin and pulp grapes showed good results for the total phenolic content. The antioxidant activities of the hydroalcoholic extracts were well-correlated with the total phenolic content and total flavonoid content. Lower values of these parameters were found for extracts obtained from skin and pulp than for those obtained from seeds of the same grape variety regardless of the culture management system (organic/conventional). Data mining techniques such as regression analysis, principal component analysis, and clustering analysis were applied to establish the potential correlation between the phytochemical content and the antioxidant activities of the red grapes on the one hand, and grape variety, anatomical parts, and vineyard type (organic/conventional) on the other hand.