Fermented Pistachio-Based Beverages as Novel Functional Foods: Improved Phenolic Bioaccessibility and Antidiabetic Properties

This study evaluated the effects of lactic acid bacteria (LAB) fermentation on the phenolic composition, bioaccessibility, and bioactive potential of pistachio-based beverages formulated from the Argentine (A) ‘Kerman’ variety and the Italian (I) ‘Bronte’ variety of pistachios. Bever- ages were fermented using either Leuconostoc pseudomesenteroides PD4 or Companilactobacillus alimentarius PG3, producing four fermented samples (APD4, APG3, IPD4, and IPG3), and two non-fermented controls (AC, IC). Fermentation markedly increased the total phenolic content (1.3–1.4-fold) and proanthocyanidins (up to 1.6-fold in APG3). Intestinal and colonic dialysates contained only quercetin, with intestinal bioaccessibility 27.6 times higher in APG3 than in AC, and colonic bioaccessibility 2.4-fold higher. Antioxidant activity (ABTS•+ assay) in- creased by 5–15% in the fermented samples, whereas FRAP remained stable. While ω-amylase inhibition decreased slightly after fermentation, ω-glucosidase inhibition reached up to 82% (IPG3), and DPP-IV inhibition peaked at 95% (IPD4). ACE-I inhibition remained high (84–93%). LAB fermentation effectively enhanced the biofunctional properties of pistachio-based bev- erages, primarily through improved polyphenol bioaccessibility and antidiabetic potential. These findings highlight lactic acid fermentation as a promising biotechnological strategy for developing novel, plant-based functional beverages with enhanced health-promoting properties.