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. Beverages 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) increased by 5–15% in the fermented samples, whereas FRAP remained stable. While α-amylase inhibition decreased slightly after fermentation, α-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 beverages, 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.