Optimization of Polyphenol Extraction From Fresh Tea Shoots for Production of the Functional Cracker: Antioxidant...

In this study, the extraction conditions for fresh green tea shoots (Camellia sinensis) were optimized using Box-Behnken design (BBD) to maximize polyphenol yield in the green tea leaf extract (GTLE). The lyophilized GTLE obtained under optimal conditions was incorporated into cracker formulations, replacing a portion of the flour. The physicochemical properties of both the GTLE and the enriched crackers were evaluated, including antioxidant capacity (AC), total polyphenol (TP), and total flavonoid (TF) contents, bioaccessibility, individual phenolic compounds (via high performance liquid chromatography (HPLC), texture, and color values). BBD optimization revealed that a solid-to-solvent (S/S) ratio of 1:50.64, extraction temperature of 95°C, and duration of 20 min were ideal for polyphenol extraction. Enriched crackers exhibited significantly higher TP and TF contents compared to control crackers, with an AC of 12.24 mmol ascorbic acid equivalent (AAE)/g dry matter (DM), whereas no antioxidant activity was detected in the control. Bioaccessibility of polyphenols decreased during both gastric and intestinal digestion stages. Phenolic compounds, such as gallic acid (GA), epigallocatechin (EGC), epigallocatechin gallate (EGCG), quercetin-3-rhamnosylglucoside (Q3RG) and kaempferol-3-rhamnosylglucoside (K3RG), were identified in enriched crackers but absent in the control. The incorporation of GTLE also resulted in a decrease in lightness (L*) and enhancement in redness (a*) and yellowness (b*) of the crackers. These findings demonstrate that GTLE enrichment enhances the functional properties of crackers, particularly their antioxidant profile, making them a promising functional food product.