Potential of guava pulps treated by ohmic heating as a delivery vehicle for probiotic bacteria: stability, functional properties, and in vitro digestibility

The growing demand for plant-based functional foods has driven the use of emerging technologies and the incorporation of probiotic cultures into fruit matrices. This study investigated the potential of ohmic heating (OH) (60, 70, and 80 °C; 10 and 20 V/cm) as an alternative to conventional heating (CH) (65 °C/30 min) in the processing of guava pulp intended for the delivery of probiotic bacteria, evaluating its effects on physicochemical attributes, bioactive compounds, and cell viability. Pulp samples fermented with Lacticaseibacillus rhamnosus GG ATCC 53103 and Bifidobacterium animalis ssp. lactis B94 were monitored for 28 days, including survival analysis and in vitro digestion. The results demonstrated that OH, especially at 70 °C/20 V/cm (OH70/20), better preserved physicochemical properties and significantly increased (p < 0.05) the retention of bioactive compounds such as total phenolics (≈6% increase), flavonoids, carotenoids, and vitamin C, resulting in greater antioxidant activity. During storage, all samples showed a reduction in pH and an increase in acidity; however, OH-treated pulps fermented with L. rhamnosus GG maintained greater stability of soluble solids and higher probiotic viability (>7.9 log CFU/g). The combination of OH and fermentation enhanced the levels of phenolics (45.71-61.09 mg GAE 100 g^-1), flavonoids (8.59-11.15 mg catechin 100 g^-1), carotenoids (375.91-467.85 μg 100 g^-1), and vitamin C (88.18-132.34 mg 100 g^-1). During in vitro digestion, recovery of cell viability was observed, particularly for OH70/20, in which L. rhamnosus GG reached 6.55 log CFU/g and B. animalis reached 6.08 log CFU/g. Overall, this study demonstrates that OH is a technology that not only better preserves the functional quality of guava pulp but also creates a protective matrix that enhances probiotic stability, making it a highly promising strategy for the development of effective fruit-based probiotic foods.