The Effect of Ultrasound and Lactic Acid Fermentation on the Selected Quality Parameters and Bioactive Compounds Content in Fermented Pumpkin (Cucurbita pepo L.)

Increasing the consumption of fruit and vegetables can be achieved by creating new products. A promising method seems to be the directed fermentation of vegetables. The aim of this study was to investigate the effect of ultrasonic pretreatment (US; 25 kHz; 5 min) and the lactic acid bacteria strain (LAB; <i>Lactiplantibacillus plantarum</i> 299v and <i>Lacticaseibacillus rhamnosus</i> GG) on the quality of fermented pumpkin (<i>Cucurbita pepo</i> L.). The pumpkin was inoculated with 5 log CFU/g of specific LAB strain. Fermentation was carried out for 7 days at 35 °C. Some samples were US treated at the washing stage. During fermentation, there was an increase in the LAB count of 3 logarithmic cycles compared to the initial inoculum. For <i>L. rhamnosus</i>, preceding fermentation by US treatment contributed to an increased bacteria count of 4 logarithmic cycles. In the case of fermentation with <i>L. rhamnosus</i>, the lactic acid content was significantly higher than for <i>L. plantarum</i>. These samples are also characterized by higher sensory properties, desirability of taste, and overall desirability. Fermentation contributed to a decrease in carotenoid and phenolic compounds content and an increase in the antioxidant capacity of the pumpkins, regardless of the bacterial strain.