RESUMEN
Sweet cherry pits, date seeds, and grape seeds are abundant fruit by-products in the Mediterranean region. Assessing their antioxidant capacity is crucial for their valorization. Grape and date seeds exhibited higher concentrations of total phenolic and flavonoid contents, and significant antioxidant capacity. Epicatechin was the main flavonoid in sweet cherry pits and date seeds (29-85 mg/g), while vanillic acid was the predominant phenolic acid across all by-products (5-23 mg/g). However, some sweet cherry pit varieties exceeded Maximum Residue Levels (MRL) for five pesticides, while grape seeds contained thirteen fungicide residues, all below MRL. Ochratoxin A was detected in one date seed but below the limit of quantification. Additionally, grape seeds showed an Al content of approximately 130 mg/kg, along with levels of As, Cd, and Pb. Date seeds exhibited high potential for food and pharmaceutical applications, pending evaluation for chemical contaminants.
RESUMEN
Oenococcus oeni is the most resistant lactic acid bacteria species to the environmental stresses encountered in wine, particularly the acidity, presence of ethanol and phenolic compounds. Indigenous strains develop spontaneously following the yeast-driven alcoholic fermentation and may perform the malolactic fermentation whereby improving taste, aroma, and the microbial stability of wine. However, spontaneous fermentation is sometimes delayed, prolonged or incomplete. In order to better control its timing and quality, O. oeni strains are selected and developed to be used as malolactic starters. They are prepared under proprietary manufacturing processes to survive direct inoculation and are predominantly provided as freeze-dried preparations. In this study, we have investigated the physiological and molecular alterations occurring in O. oeni cells prepared by an industrial process that consists of preconditioning protocols and freeze-drying, and compared them to the same strain grown in a grape juice medium. We found that compared to cultured cells, the industrial production process improved survival under extreme conditions, i. e. at low pH or high tannin concentrations. In contrast, cultured cells resumed active growth more quickly and strongly than freeze-dried preparations in standard pH wines. A proteomic analysis showed that during the industrial production most non-essential metabolic processes are shut down and components of the general and the stringent stress response are upregulated. The presence of major components of the stress response facilitates protein homeostasis and physiological changes that further ensure the integrity of cells.