Beatriz Gullón

Effects of added Lactobacillus acidophilus and Bifidobacterium lactis probiotics on the quality characteristics of goat ricotta and their survival under simulated gastrointestinal conditions

This study evaluated the effects of incorporating the probiotics Bifidobacterium animalis subsp. lactis Bb-12 (B. lactis) or Lactobacillus acidophilus La-05 (L. acidophilus) into goat ricotta on the technological, physicochemical, physical and sensory parameters of this product during refrigerated storage, as well as the protective effects of the goat ricotta on the survival of the tested probiotics during exposure to simulated gastrointestinal conditions. Incorporating the tested probiotics did not affect the yield or syneresis of the obtained goat ricotta. The counts of L. acidophilus and B. lactis during the chosen storage period were approximately 6 log CFU/g. The ricotta samples containing a probiotic strain presented smaller and greater amounts of lactose and lactic acid, respectively, and exhibited greater hardness and lower brightness after storage compared with the samples lacking a probiotic. No differences were observed in the fatty acid profiles of the goat ricotta containing or not containing a probiotic. All of the ricotta samples were described as a soft cheese with a homogeneous texture; however, the goat ricotta cheeses containing L. acidophilus or B. lactis were described as having a more acidic flavor. At the end of a challenge using experimental human digestive conditions, the counts of each of the tested probiotic strains were approximately 6 log CFU/g if it had been incorporated into goat ricotta. These results demonstrated the feasibility of incorporating L. acidophilus or B. lactis into goat ricotta because these probiotics did not negatively affect the quality characteristics of this product and suggested that goat ricotta is an efficacious food matrix for maintaining the viability of these probiotics during storage and under the stressful conditions imposed by the human gastrointestinal tract.

Evaluation of the prebiotic potential of arabinoxylans from brewer’s spent grain

Arabinoxylans (AX) consumption has been related to the treatment and prevention of cardiovascular diseases, type II diabetes, colorectal cancer and obesity. The beneficial health effects are conferred through gut microbiota modulation, and therefore, they have been proposed as potential slowly fermentable prebiotic candidates. As the mechanisms are not yet well understood, the prebiotic potential of AX from brewer’s spent grain (BSG) has been investigated. Two types of AX from BSG (AX1 and AX2) of different length and branching averages were fermented with human faecal inocula and compared to fermented cultures containing a commercial prebiotic (fructooligosaccharide (FOS)) and cultures with no added carbohydrate (control). Results demonstrated that the AX were extensively metabolised after 48xa0h of fermentation. The pH decreased along fermentation and the lowest value was achieved in AX1 cultures. The production of short chain fatty acids (SCFA) was higher in AX cultures than in cultures containing FOS and controls, with AX1 presenting the highest concentrations. The stimulatory effect of beneficial bacteria was higher in AX cultures, and AX2 presented the highest positive effect. Prebiotic potential of AX from BSG was confirmed by the production of SCFA and the modulation of gut microbiota, especially by the high increase in bifidobacteria populations.

Effects of hemicellulose-derived saccharides on behavior of Lactobacilli under simulated gastrointestinal conditions

Four types of purified xylooligosaccharides (XOS) from several lignocellulosic materials, showing different structural features (including chain length, branching, and linkage types), obtained from different feedstocks (Eucalyptus globulus wood, rice husks, wheat bran or barley wastes), were assessed (using fructooligosaccharides as reference substrate) for their effects on the growth of six different probiotic Lactobacillus strains in basal MRS media and survival in different simulated gastrointestinal tract (GIT) conditions. The hydrophobicity of bacterial cells, which measures their potential for epithelial adhesion, was also evaluated. Improved growth of Lactobacillus strains was observed for media containing XOS as the single source of carbohydrate, confirming their role as prebiotics. These oligosaccharides also led to improvement in the resistance of the target Lactobacillus to the simulated GIT environment. The enhancement of the survival rates depended on the type of oligosaccharide. This is the first comparative study of the effects in lactobacilli involving four types of XOS obtained from different lignocellulosic materials. The obtained results show that these oligosaccharides manufactured from alternative sources could be interesting prebiotic substrates with different structures in comparison with the available commercially and with interesting potential towards the development of synbiotic products.

Influence of the addition of Lactobacillus acidophilus La-05, Bifidobacterium animalis subsp. lactis Bb-12 and inulin on the technological, physicochemical, microbiological and sensory features of creamy goat cheese

The effects of the addition of Lactobacillus acidophilus LA-05, Bifidobacterium animalis subsp. lactis BB-12 and inulin on the quality characteristics of creamy goat cheese during refrigerated storage were evaluated. The manufactured cheeses included the addition of starter culture (Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris - R-704) (CC); starter culture, L. acidophilus LA-05 and inulin (CLA); starter culture, B. lactis BB-12 and inulin (CBB); or starter culture, L. acidophilus LA-05, B. lactis BB-12 and inulin (CLB). In the synbiotic cheeses (CLA, CBB and CLB), the counts of L. acidophilus LA-05 and B. lactis BB-12 were greater than 6logu2009CFU g-1, the amount of inulin was greater than 6 g per 100 g, and the firmness was reduced. The cheeses evaluated had high brightness values (L*), with a predominance of yellow (b*). CC had higher contents of proteins, lipids and minerals compared to the other cheeses. There was a decrease in the amount of short-chain fatty acids (SCFAs) and an increase of medium-chain (MCFAs) and long-chain fatty acids (LCFAs) in the synbiotic cheeses compared to CC. The amount of conjugated linoleic acid increased in CLA, CBB and CLB. The highest depth of proteolysis and the greatest changes in the release of free amino acids were found in CLB. The addition of inulin and probiotics, alone or in co-culture, did not affect the cheese acceptance. Inulin and probiotics can be used together for the production of creamy goat cheese without negatively affecting the general quality characteristics of the product, and to add value because of its synbiotic potential.