This study integrated a gelatin-sodium alginate composite hydrogel system with 3D bioprinting technology to construct a functional starter culture with a dual-layered spatial structure that allows for its fast and slow release, aiming to enhance the survival and metabolic stability of Lacticaseibacillus paracasei PC18 in blueberry juice, highly acidic and rich in polyphenols. The results showed that this dual-layered model achieved spatiotemporally controlled release of lactic acid bacteria: the outer CaCl₂ layer promoted rapid initiation in the early fermentation stage, significantly increasing viable cell count; the inner calcium ethylenediaminetetraacetate (EDTA-Ca) layer continuously released calcium during the mid-to-late fermentation stages, maintaining microbial viability and metabolic stability, with the final viable bacterial count reaching 8.75 (lg(CFU/mL)), pH steadily decreasing to 3.82, and total acid accumulation reaching 177.74 mg/L. Furthermore, the starter effectively improved the retention and transformation of functional components: the total phenol concentration reached 1158.02 mg/L at 48 h, the anthocyanin concentration peaked at 9.14 mg/L at 12 h, and the starter demonstrated stable antioxidant performance, scavenging 62.12% of 2,2’-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation and 69.87% of 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) radical after 72 h of fermentation. This study confirms that the multi-calcium source 3D printing strategy synergistically optimizes the fermentation process, offering an effective solution to address the decline in microbial viability and insufficient metabolic regulation during acidic juice fermentation, thereby demonstrating potential for the development of functional fermented foods.

In this study, soybean protein isolate (SPI) and blueberry anthocyanins (BANs) complex (HPPM-SPI-BANs) treated by high power pulsed microwave (HPPM) was prepared, and its physicochemical properties and biological activity were evaluated. The effect of HPPM treatment on the functional properties and biological activity of SPI was studied. In addition, the effect of partial replacement of egg white protein by HPPM-SPI-BANs on the baking quality and storage properties of cake was evaluated. The results indicated that HPPM treatment significantly improved the solubility of HPPM-SPI-BANs by 2.11 folds, and improved the foaming and emulsifying properties (P < 0.05). The antioxidant activity was also significantly improved compared with SPI and SPI-BANs complex without HPPM treatment. Moreover, the addition of HPPM-SPI-BANs inhibited water loss during cake baking and improved the hardness and chewiness of cake. The 2,2-diphenyl-1-picryhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power of cake with HPPM-SPI-BANs increased by 4.56 and 3.79 folds, respectively, and the aging rate constant k decreased to 0.12. Accordingly, HPPM-SPI-BANs plays an important role in improving the shelf life quality of cake.