Indigenous Lactococcus lactis with probiotic properties: Evaluation of wet, thermally- and freeze-dried raisins as supports for cell immobilization, viability and aromatic profile in fresh curd cheese

Indigenous Lactococcus lactis enriched raisins were incorporated in fresh curd cheese in wet, thermally dried, and freeze-dried form to produce a novel probiotic dairy product. Probiotic properties of Lactococcus lactis LL16 were evaluated in previous studies. Thus in this study the viability of L. lactis cells was assessed in the cheeses during storage at 4 °C for 1, 7, and 14 days and the effect of the added enriched raisins on physicochemical parameters, microbiological characteristics, sugar content, aromatic profile and sensory acceptance of cheeses were evaluated. Results showed that the nature of L. lactis LL16 (free or immobilized cells), the support (raisins/immobilized cells on raisins) and the nature of immobilized cultures on raisins (wet or dried) had a significant (p < 0.05) effect on cheese pH, moisture, and lactococci counts. Immobilized L. lactis cells maintained viability at necessary levels (> 6 cfu/g) during storage and significantly increased the acceptability of cheese. Control cheeses were the least acceptable, while cheese samples with L. lactis and raisins, which had the highest lactococci counts, expressed the highest scores in overall sensory acceptability among all samples. Only the addition of thermally dried raisins with immobilized L. lactis LL16 cells resulted in an increased cheese sensory acceptability by the end of the storage. This finding might me influenced by a significant increase in total sugars and volatile compounds in this sample. Overall, the addition of raisins enhanced the volatile profile of cheeses with 2-furanmethanol, 1-octanol, 3-methylbutanal, 2-methylbutanal, 2-furancarboxaldehyde, 1-(2-furanyl)-ethanone, 5-methyl-2-furancarboxaldehyde. The obtained results are encouraging for the production of novel fresh cheeses with improved sensorial and probiotic characteristics on industrial and/or small industrial scale. This project has received funding from European Regional Development Fund (project No 01.2.2-LMT-K-718-01-0032) under grant agreement with the Research Council of Lithuania (LMTLT).Indigenous Lactococcus lactis enriched raisins were incorporated in fresh curd cheese in wet, thermally dried, and freeze-dried form to produce a novel probiotic dairy product. Probiotic properties of Lactococcus lactis LL16 were evaluated in previous studies. Thus in this study the viability of L. lactis cells was assessed in the cheeses during storage at 4 °C for 1, 7, and 14 days and the effect of the added enriched raisins on physicochemical parameters, microbiological characteristics, sugar content, aromatic profile and sensory acceptance of cheeses were evaluated. Results showed that the nature of L. lactis LL16 (free or immobilized cells), the support (raisins/immobilized cells on raisins) and the nature of immobilized cultures on raisins (wet or dried) had a significant (p < 0.05) effect on cheese pH, moisture, and lactococci counts. Immobilized L. lactis cells maintained viability at necessary levels (> 6 cfu/g) during storage and significantly increased the acceptability of cheese. Control cheeses were the least acceptable, while cheese samples with L. lactis and raisins, which had the highest lactococci counts, expressed the highest scores in overall sensory acceptability among all samples. Only the addition of thermally dried raisins with immobilized L. lactis LL16 cells resulted in an increased cheese sensory acceptability by the end of the storage. This finding might me influenced by a significant increase in total sugars and volatile compounds in this sample. Overall, the addition of raisins enhanced the volatile profile of cheeses with 2-furanmethanol, 1-octanol, 3-methylbutanal, 2-methylbutanal, 2-furancarboxaldehyde, 1-(2-furanyl)-ethanone, 5-methyl-2-furancarboxaldehyde. The obtained results are encouraging for the production of novel fresh cheeses with improved sensorial and probiotic characteristics on industrial and/or small industrial scale. This project has received funding from European Regional Development Fund (project No 01.2.2-LMT-K-718-01-0032) under grant agreement with the Research Council of Lithuania (LMTLT).