Influence of the Type of Sauerkraut Fermentation with Probiotics Strains on Folate Content, Antioxidant Activity and Sensory Analysis

Sauerkraut (SK) is a fermented food of plant origin recognised for its nutritional properties and health benefits. It is traditionally produced through spontaneous fermentation, carried out by the native microflora of fresh cabbage, which includes Gram-negative bacteria, moulds, yeasts and finally lactic acid bacteria (LAB), responsible for transforming natural sugars into lactic acid. However, spontaneous fermentation can also promote the growth of undesirable microorganisms, leading to risks of sensory or food safety alterations, such as the production of biogenic amines. To prevent these limitations, the use of LAB starter cultures is presented as a promising alternative. This study evaluated the fermentation of cabbage at 18 °C and 25 °C, comparing spontaneous fermentation with controlled fermentations using probiotic cultures (Lactiplantibacillus plantarum 229v and Lacticaseibacillus rhamnosus GG). Due to its nutritional importance, the folate content of different types of SK has been studied. Spontaneous fermentation showed positive results in all studied parameters; however, L. plantarum 229v was the inoculum with the highest and fastest acidifying efficacy, reducing the pH to below 4.0 after 7 days at both temperatures. At 25 °C, L. plantarum 229v achieved LAB counts higher than those of L. rhamnosus GG (7.02 vs. 6.00 log CFU·g−1) and exerted the most effective control over enterobacteria and moulds/yeasts, reaching undetectable values (0 log CFU·g−1) on day 7 under both conditions. Antioxidant activity after 42 days of fermentation was higher at 18 °C with L. rhamnosus GG, which showed the highest values (up to 3.50 mg CE·g−1 FW), followed by L. plantarum 229v and spontaneous fermentation. In terms of total folate content (TFC) retention, spontaneous fermentation was particularly effective at both temperatures after 42 days of fermentation (794.741 µg/100 g TFC at 18 °C and 586.542 µg/100 g TFC at 25 °C). In sensory analysis, spontaneous fermentation, in general acceptance, was rated highest (6.2), followed by L. plantarum 229v (5.5) and L. rhamnosus GG (5.3). Considering all the factors studied, SK fermentation with the probiotic strain L. plantarum 229v has proven to be the most suitable.