Enhanced aroma and flavour profile of fermented Tetragonula pagdeni Schwarz honey by a novel yeast T. delbrueckii GT-ROSE1 with superior fermentability

Beside a source of bioactive compounds, honey represents untapped-reservoir of beneficial microbes. Next generation sequencing technology was applied to aid the discovery of newly-isolated flavour yeast Torulaspora delbrueckii strain GT-ROSE1 from honey samples. Owing to the presence of natural duplicate regulatory sites in aromatic genes, it was used to create value-added fermented honey with unique aroma-flavour profile. This osmophilic strain could assimilate different carbons and tolerated to low pHs, high ethanol and sugars, exhibiting useful traits for food and alcoholic fermentation of sugar-based industries. Global analysis of aroma-flavour profile revealed higher total concentrations of key compounds after fermentation by GT-ROSE1, compared to commercial wine yeasts. Twenty-four volatile compounds were identified using a nontargeted HS-SPME-GC-MS method. High odour activity values and quantitative sensory analysis indicated fruity and rose flowery aroma of key compounds nonanol and 2-phenylethanol, respectively. Importantly, fermented Tetragonula pagdeni Schwarz honey with observed excellent antioxidant property displayed appealing characteristic of enhanced 2-phenylethanol of rose-like flavour with odour threshold of 16.08. Thus, flavour yeast could be used to improve chemical content and enhance sensory value of local food products.

Cross-linked alginate edible coatings incorporated with hexyl acetate: Film characteristics and its application on fresh-cut rose apple

Edible coatings,as carriers of antimicrobial compounds,have been proposed as an alternative method to preserve fresh-cut products.This research focused to improve the shelf life of fresh-cut rose apples by applying an edible coating based on alginate cross-linked with calcium chloride(SAC)-enriched hexyl acetate(HA)as a natural antimicrobial compound.The SAC with HA in 0.01,0.03,and 0.05%(v/v)(SAC-HA)solution was evaluated for its film properties and applied to fresh-cut rose apples,and compared with the unmodified SAC coating.Postharvest quality and microbial contamination were determined every 2 days during 10 days of storage at 4℃.The film thickness,tensile strength,and elongation at break increased with the high concentrations of HA added.Films containing 0.03%HA had lower oxygen permeability(from 1.57 to 0.04×10^(-7) cm^(3)μm m^(-2) day^(-1) kPa^(-1)),as well as water vapor permeability(from 0.03 to 0.01 g mm m^(-2) day^(-1) kPa^(-1)),compared to the unmodified SAC film.Moreover,the greater coating uniformity and thickness were supported by scanning electron microscopy and Fourier transform infrared spectroscopy.The developed edible SAC coatings with 0.03%HA successfully preserved the physicochemical quality and extended the shelf life of fresh-cut rose apples for 10 days at 4℃ by retarding the respiration rate,inhibiting browning,and preventing microbial growth.Therefore,the using of SAC-HA in fresh-cut products is a promising and safe preservation technique to extend shelf life.