Direct Application of Rep-PCR on Type I Sourdough Matrix to Monitor the Dominance and Persistence of a Lactobacillus plantarum Starter Throughout Back-Slopping

Commercial Organic Versus Conventional Whole Rye and Wheat Flours for Making Sourdough Bread: Safety, Nutritional, and Sensory Implications

Organic farming is gaining a broad recognition as sustainable system, and consumer demand for organic products has increased dramatically in the recent past. Whether organic agriculture delivers overall advantages over conventional agriculture is, however, contentious. Here, the safety, nutritional, and sensory implications of using commercial organic rye, soft, and durum wheat flours rather than conventional-made sourdough bread have been investigated. Culture-dependent and culture-independent approaches were used to explore the microbial architecture of flours and to study their dynamics during sourdough propagation. Besides biochemical features, the main nutritional (amino acid content, asparagine level, and antioxidant activity) characteristics of sourdoughs were investigated, and their effect on the structural, nutritional, and sensory profiles of breads assessed. Overall, the organic farming system led to flours characterized by lower content of asparagine and cell density of Enterobacteriaceae while showing higher concentration of total free amino acids. Differences of the flours mirrored those of sourdoughs and breads. The use of sourdough fermentation guaranteed a further improvement of the flour characteristics; however, a microbial and sensory profile simplification as well as a slight decrease of the biochemical parameters was observed between breads with sourdough after one-cycle fermentation and 10 days of propagation.

Dynamic interactions of lactic acid bacteria in Korean sourdough during back-slopping process

AIMS

This study aimed to clarify the cause of quality reduction in Korean sourdough after successive back-slopping.

METHODS AND RESULTS

We investigated the dynamic changes in lactic acid bacteria during the back-slopping process using genetic fingerprinting techniques. During the initial propagation phases, the dominant lactic acid bacteria were Fructilactobacillus sanfranciscensis (<5 log CFU per g sourdough), Latilactobacillus curvatus (9·5 log CFU per g sourdough) and Levilactobacillus brevis (6·5 log CFU per g sourdough). However, after the 11th propagation, F. sanfranciscensis became more prominent (>9·0 log CFU per g sourdough), whereas L. curvatus and L. brevis rapidly decreased. Monitoring these bacteria in the co-culture system revealed that acid-tolerant F. sanfranciscensis rapidly utilized maltose (1·65 g l^-1  h^-1 ) and produced large amounts of lactic acid, whereas L. brevis and L. curvatus consumed maltose slowly and L. curvatus was poorly tolerant to lactic acid.

CONCLUSION

The results indicate that competition exists between the lactic acid bacteria in sourdough during the back-slopping process, and microbial succession by acid-tolerant species results in quality reduction of sourdough.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study uncovered the cause of microbial changes during the propagation of Korean sourdough and proposed a strategy to develop starters to produce high-quality bakery products.

Lactic acid bacteria diversity in corn silage produced in Minas Gerais (Brazil)

Purpose

The diversity of lactic acid bacteria (LAB) in silages produced in warm climate countries is not well known. This study aimed to identify and characterise the metabolic and genotypic aspects of autochthonous LAB isolated from corn silage produced in the state of Minas Gerais, Brazil.

Methods

Eighty-eight LAB were isolated. To evaluate their performance at the strain level, all isolates were distinguished among strains using random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) and repetitive extragenic palindromic PCR (REP-PCR) techniques. The organic acid and ethanol production were determined by high-performance liquid chromatography (HPLC).

Result

The fingerprints obtained by RAPD-PCR with a M13 primer were more discriminatory than those obtained with the REP-PCR technique using a (GACA)4 primer. Moreover, 28 representative isolates were identified as Lactobacillus acidophilus, L. buchneri, L. casei, L. diolivorans, L. hilgardii, L. paracasei, L. parafarraginis, L. plantarum, L. rhamnosus, L. zeae and Pediococcus acidilactici. Different fingerprinting profiles between isolates within the same species were observed. However, some strains isolated from different silages showed the same band profile, thus suggesting the presence of clusters with high similar fingerprints in silages from various regions.

Conclusion

A variation in LAB diversity was observed in the silages of the evaluated regions, with L. rhamnosus and L. buchneri showing the highest distribution. Differences in organic acid production were observed among the strains belonging to the same species. This research contributes to a better understanding of the LAB community present in corn silage produced in warm climates. These strains will be studied as potential silage starters.