2,5-Diketopiperazines (2,5-DKPs), naturally occurring in food and beverages, have demonstrated notable antimicrobial properties. However, their synergism with other secondary metabolites in real food matrices remains largely unexplored. In our study, a group of microbially produced 2,5-DKPs, including proline-based dilactams (Pro-DKPs), was synthesized and evaluated for their efficacy against common foodborne pathogens: CCM 4516, CCM 4517, CCM 1961, DBM 4062, CCM 8189, and DMF 0109. We also investigated the impact of the polarity of 2,5-DKPs on their antimicrobial effect. Among the four synthesized 2,5-DKPs, cyclo-(l-Leu-l-Pro) (Pro-DKP-1) inhibited the growth of DMF 0109 by up to 83%, as determined using the poisoned plate method. Further experiments investigated the synergistic effects of Pro-DKPs in combination with lactic acid at food-relevant concentrations. The addition of lactic acid considerably enhanced the antimicrobial activity of all three Pro-DKPs, with inhibitions reaching up to 99% against DMF 0109. Our findings suggest that employing commercial starter cultures capable of producing 2,5-DKPs, including Pro-DKPs, may offer a promising strategy for extending the shelf life of food products and beverages.

Buckwheat is a pseudocereal with significant nutritional qualities and a wide potential for use in the food industry. Buckwheat flours were characterized and they were subsequently used for the preparation of gluten-free sourdoughs. Buckwheat sourdoughs were made under different process conditions (sourdough yield, time, temperature, the presence of a starter fermentation culture) and analysed (pH, TTA, microbiology assessment). The prepared sourdoughs were successfully used as bread recipe ingredients. The antifungal activity of sourdough bread was determined.

Previously undescribed species of Limosilactobacillus fermentum isolated from wholemeal buckwheat sourdough were identified by MALDI-TOF/MS and 16S rRNA analysis. The metabolism of 6 hydroxycinnamic acids by L. fermentum 6P1, 6P2 and 7P2 strains provided mostly o-, m-, p-dihydrocoumaric, dihydroferulic, dihydrocaffeic and dihydrosinapic acids. The ratio of hydroxyphenylpropionic acids to 4-vinylphenols was strain-to-strain specific. Decarboxylation of free cinnamic acid to potentially toxic styrene was low (1.8–23.9 mol. %) in all Limosilactobacillus strains tested. At a concentration of 13.6 mmol/L, reduced p-dihydrocoumaric and dihydroferulic acids were shown to cause less growth inhibition than their precursors, while specific growth rates μ increased significantly. L. fermentum POH with the highest sensitivity to phenolic acids exhibited the lowest ability to reduce hydroxycinnamic acids (11.8–44.5%) by phenolic acid reductase. Metabolomic experiments with chemically labelled D-glucose-d12 provided a deeper insight into electron transfer to polyphenols as the final acceptor. To the best of our knowledge, deuterium transfer to dideuteroferulic acid was observed for the first time.

In this study, two strains of Lactiplantibacillus plantarum 299v and CCDM 181 were tested for their ability to grow in milk and soy beverage, for stability during cold storage of fermented beverages, compatibility with yoghurt culture and activity against yeasts. Both strains grew better in soy drink compared to milk. During co-culturing with the yoghurt culture, sufficient acidification of milk and soy beverage necessary for the production of fermented products was achieved. The stability of tested strains in media at pH 4.5 for 28 days at 5 °C was good. L. plantarum was effective in the inhibition of undesirable yeast growth, but the ability was strain-specific. Tested strains demonstrated also a strain-specific ability to suppress the growth of yoghurt culture bacteria. For a possible application of co-culturing L. plantarum with the yoghurt culture, verification of the mutual compatibility of specific strains is necessary.

Research groups have put significant emphasis on the evaluation of nutritional, health-promoting, and other biological activities of secondary metabolites from buckwheat. Among these phytochemicals, phenolic and lipophilic antioxidants, particularly, phenolic acids, flavonoids, and tocopherols, have been the focus of the latest studies since antioxidant activity has recently been associated with the possibility of inhibiting fungal growth and mycotoxin biosynthesis. The mycotoxin contamination of cereal and pseudocereal grains caused primarily by Fusarium, Penicillium, and Aspergillus species poses a significant hazard to human health. Therefore, efforts to examine the involvement of plant antioxidants in the biosynthesis of mycotoxins at the transcriptional level have emerged. In addition, hydrophobic interactions of buckwheat phenolics with cell membranes could also explain their capacity to reduce fungal development. Eventually, possibilities of enhancing the biological activity of cereal and pseudocereal phytochemicals have been studied, and sourdough fermentation has been proposed as an efficient method to increase antioxidant activities. This effect could result in an increased antifungal effects of sourdough and bakery products. This review reports the main advances in research on buckwheat phenolics and other antioxidant phytochemicals, highlighting possible mechanisms of action and processes that could improve their biological activities.

Research groups have put significant emphasis on the evaluation of nutritional, health-promoting, and other biological activities of secondary metabolites from buckwheat. Among these phytochemicals, phenolic and lipophilic antioxidants, particularly, phenolic acids, flavonoids, and tocopherols, have been the focus of the latest studies since antioxidant activity has recently been associated with the possibility of inhibiting fungal growth and mycotoxin biosynthesis. The mycotoxin contamination of cereal and pseudocereal grains caused primarily by Fusarium, Penicillium, and Aspergillus species poses a significant hazard to human health. Therefore, efforts to examine the involvement of plant antioxidants in the biosynthesis of mycotoxins at the transcriptional level have emerged. In addition, hydrophobic interactions of buckwheat phenolics with cell membranes could also explain their capacity to reduce fungal development. Eventually, possibilities of enhancing the biological activity of cereal and pseudocereal phytochemicals have been studied, and sourdough fermentation has been proposed as an efficient method to increase antioxidant activities. This effect could result in an increased antifungal effects of sourdough and bakery products. This review reports the main advances in research on buckwheat phenolics and other antioxidant phytochemicals, highlighting possible mechanisms of action and processes that could improve their biological activities.