Lactobacilli in sourdough fermentation

Diversity and dynamics of sourdough lactic acid bacteriota created by a slow food fermentation system

Sourdough is a naturally fermented dough that is used worldwide to produce a variety of baked foods. Various lactic acid bacteria (LAB), which can determine the quality of sourdough baked foods by producing metabolites, have been found in the sourdough ecosystem. However, spontaneous fermentation of sourdough leads to unpredictable growth of various micro-organisms, which result in unstable product quality. From an ecological perspective, many researchers have recently studied sourdough LAB diversity, particularly the elucidation of LAB community interactions and the dynamic mechanisms during the fermentation process, in response to requests for the control and design of a desired sourdough microbial community. This article reviews recent advances in the study of sourdough LAB diversity and its dynamics in association with unique characteristics of the fermentation system; it also discusses future perspectives for better understanding of the complex sourdough microbial ecosystem, which can be attained efficiently by both in vitro and in situ experimental approaches.

Fermentative Foods: Microbiology, Biochemistry, Potential Human Health Benefits and Public Health Issues

Fermented foods identify cultures and civilizations. History, climate and the particulars of local production of raw materials have urged humanity to exploit various pathways of fermentation to produce a wide variety of traditional edible products which represent adaptations to specific conditions. Nowadays, industrial-scale production has flooded the markets with ferments. According to recent estimates, the current size of the global market of fermented foods is in the vicinity of USD 30 billion, with increasing trends. Modern challenges include tailor-made fermented foods for people with special dietary needs, such as patients suffering from Crohn's disease or other ailments. Another major challenge concerns the safety of artisan fermented products, an issue that could be tackled with the aid of molecular biology and concerns not only the presence of pathogens but also the foodborne microbial resistance. The basis of all these is, of course, the microbiome, an aggregation of different species of bacteria and yeasts that thrives on the carbohydrates of the raw materials. In this review, the microbiology of fermented foods is discussed with a special reference to groups of products and to specific products indicative of the diversity that a fermentation process can take. Their impact is also discussed with emphasis on health and oral health status. From Hippocrates until modern approaches to disease therapy, diet was thought to be of the most important factors for health stability of the human natural microbiome. After all, to quote Pasteur, "Gentlemen, the microbes will have the last word for human health." In that sense, it is the microbiomes of fermented foods that will acquire a leading role in future nutrition and therapeutics.

Functional Properties and Sustainability Improvement of Sourdough Bread by Lactic Acid Bacteria

Preventing food spoilage without the addition of chemical food additives, while increasing functional properties of wheat-based bakery products, is an increasing demand by the consumers and a challenge for the food industry. Within this study, lactic acid bacteria (LAB) isolated from sourdough were screened in vitro for the ability to utilize the typical wheat carbohydrates, for their antimicrobial and functional properties. The dual culture overlay assay revealed varying levels of inhibition against the examined fungi, with Lactiplantibacillus plantarum S4.2 and Lentilactobacillusparabuchneri S2.9 exhibiting the highest suppression against the indicator strains Fusarium graminearum MUCL43764, Aspergillus fumigatus, A. flavus MUCL11945, A. brasiliensis DSM1988, and Penicillium roqueforti DSM1079. Furthermore, the antifungal activity was shown to be attributed mainly to the activity of acids produced by LAB. The antibacillus activity was evaluated by the spot-on-the-lawn method revealing a high inhibition potential of the majority of LAB isolated from sourdough against Bacillus cereus DSM31, B. licheniformis DSM13, B. subtilis LMG7135, and B. subtilis S15.20. Furthermore, evaluating the presence of the glutamate decarboxylase gen in LAB isolates by means of PCR showed a strain dependency of a potential GABA production. Finally, due to improved functional activities, LAB isolated from sourdoughs exhibit promising characteristics for the application as natural preservatives in wheat-based bakery products.

Technological Performance and Selection of Lactic Acid Bacteria Isolated from Argentinian Grains as Starters for Wheat Sourdough

The selection of lactic acid bacteria strains is interesting for the development of sourdough to obtain wheat bread with improved technological and nutritional properties. In this work, the performance of ten different LAB strains isolated from diverse cereals in wheat sourdough was evaluated. Five facultative heterofermentative (Lactobacillus pentosus ES124, Lactobacillus paralimentarius ES259, Lactobacillus plantarum ES137, Lactobacillus plantarum ATCC8014 and Lactobacillus plantarum ES147), three obligately heterofermentative (Lactobacillus brevis ES253, Lactobacillus fermentum ES142 and Lactobacillus fermentum ES148) and two homofermentative (Pediococcus acidilactici ES22 and Enterococcus faecium ES74) lactic acid bacteria strains were evaluated in ten single strain fermentations. Sugar profile, volatile compounds and proteolytic ability of sourdoughs were analyzed. The microbiological counts showed that facultative heterofermentative strains presented higher counts than homofermentative sourdoughs. Monosaccharides (glucose and fructose), maltose and sucrose, isomaltose and dextrin were detected in fermentations with homofermentative strains whilst in those with heterofermentative strains maltose/sucrose, isomaltose and dextrin were found. L. paralimentarius ES259 and L. pentosus ES124 showed the highest diversity of volatile compounds. L. plantarum ES137 and P. acidilactici ES22 were the strains with the highest proteolytic activity. The technological performance allowed us to select LAB as starters to develop breads with specific rheological properties and final quality.

Intraspecies diversity and genome-phenotype-associations in Fructilactobacillus sanfranciscensis

In this study the intraspecies diversity of Fructilactobacillus (F.) sanfranciscensis (formerly Lactobacillus sanfranciscensis) was characterized by comparative genomics supported by physiological data. Twenty-four strains of F. sanfranciscensis were analyzed and sorted into six different genomic clusters. The core genome comprised only 43,14 % of the pan genome, i.e. 0.87 Mbp of 2.04 Mbp. The main annotated genomic differences reside in maltose, fructose and sucrose as well as nucleotide metabolism, use of electron acceptors, and exopolysacchride formation. Furthermore, all strains are well equipped to cope with oxidative stress via NADH oxidase and a distinct thiol metabolism. Only ten of 24 genomes contain two maltose phosphorylase genes (mapA and mapB). In F. sanfranciscensis TMW 1.897 only mapA was found. All strains except those from genomic cluster 2 contained the mannitol dehydrogenase and should therefore be able to use fructose as external electron acceptor. Moreover, six strains were able to grow on fructose as sole carbon source, as they contained a functional fructokinase gene. No growth was observed on pentoses, i.e. xylose, arabinose or ribose, as sole carbon source. This can be referred to the absence of ribose pyranase rbsD in all genomes, and absence of or mutations in numerous other genes, which are essential for arabinose and xylose metabolism. Seven strains were able to produce exopolysaccharides (EPS) from sucrose. In addition, the strains containing levS were able to grow on sucrose as sole carbon source. Strains of one cluster exhibit auxotrophies for purine nucleotides. The physiological and genomic analyses suggest that the biodiversity of F. sanfranciscensis is larger than anticipated. Consequently, "original" habitats and lifestyles of F. sanfranciscensis may vary but can generally be referred to an adaptation to sugary (maltose/sucrose/fructose-rich) and aerobic environments as found in plants and insects. It can dominate sourdoughs as a result of reductive evolution and cooperation with fructose-delivering, acetate-tolerant yeasts.

Quinoa Sourdough Fermented with Lactobacillus plantarum ATCC 8014 Designed for Gluten-Free Muffins—A Powerful Tool to Enhance Bioactive Compounds

Lactobacillus plantarum ATCC 8014 was used to ferment quinoa flour, in order to evaluate its influence on the nutritional and rheological characteristics of both the sourdough and muffins. The quantification of carbohydrates and organic acids was carried out on a HPLC-RID system (high-performance liquid chromatography coupled with with refractive index detector), meanwhile HPLC-UV-VIS (high-performance liquid chromatography coupled with UV-VIS detector), AAS (Atomic absorption spectrophotometry), aluminum chloride colorimetric assay, Folin–Ciocalteu, and 1,1-Diphenyl-2-picrylhydrazyl radical scavenging activity (DPPH) methods were used to determine folic acid, minerals, flavonoids, total phenols, and radical scavenging activity, respectively. Two types of sourdough were used in this study: quinoa sourdough fermented with L. plantarum ATCC 8014 and quinoa sourdough spontaneous fermented. The first one influenced the chemical composition of muffins in terms of decreased content of carbohydrates, higher amounts of both organic acids and folic acid. Furthermore, higher amounts of flavonoids, total phenols and increased radical scavenging activity were recorded due to the use of Lactobacillus plantarum ATCC 8014 strain. These results indicate the positive effect of quinoa flour fermentation with the above strain and supports the use of controlled fermentation with lactic acid bacteria for the manufacturing of gluten free baked products.

Persistence and Effect of a Multistrain Starter Culture on Antioxidant and Rheological Properties of Novel Wheat Sourdoughs and Bread

Food consumers make decisions primarily on the basis of a product's nutritional, functional, and sensorial aspects. In this context, this study evaluated the persistence in sourdough of a multistrain starter culture from laboratory to bakery plant production and the effect of the starter on antioxidant and rheological properties of sourdoughs and derived bread. Lactobacillus sanfranciscensis B450, Leuconostoc citreum B435, and Candida milleri L999 were used as a multispecies starter culture to produce a sourdough subsequently used to modify two traditional sourdoughs to make novel bread with improved health and rheological properties. Both these novel bakery sourdoughs showed the persistence of L. sanfranciscensis B450 and C. milleri L999, and showed a significantly different lactic acid bacteria (LAB) concentration from the traditional sourdoughs. The novel sourdough PF7 M had a higher phenolic content (170% increase) and DPPH (8% increase) than the traditional bakery sourdough PF7 F. The novel sourdough PF9 M exhibited an improvement in textural parameters. Further research would be useful on the bioavailability of bio-active compounds to obtain bread with improved characteristics.

Development and Optimization of Djulis Sourdough Bread Using Taguchi Grey Relational Analysis

Bakery products made from naturally fermented sourdough show a diversified flavor and nutritional profile. Djulis (Chenopodium formosanum), known as red quinoa or Taiwan djulis, originally cultivated by Taiwanese indigenous people in mountain areas in eastern and southern Taiwan, has a high nutritional value and characteristic properties. In the present study, a new bakery product (djulis sourdough bread) was developed and a combination of the Taguchi method coupled with grey theory was utilized to optimize the baking parameters (product formulation). Five main factors, i.e., djulis sourdough (A), hulled djulis (B), oil type (C), a mixture of bread flour (wet gluten content of 29.0%) and a high-gluten flour (wet gluten content of 35.5%) (D), and honey (E), (each at four levels) were chosen for the Taguchi experiment design (L₁₆(4)⁵). Dependent parameters were the data from texture profile analysis (brittleness, springiness, cohesiveness, gumminess, and chewiness), color analysis (L*, a*, and b*), and sensory evaluation (appearance, aroma, bitterness, sourness, chewiness, and overall acceptance) of the final product. Taguchi grey relational analysis successfully determined the optimal conditions based on combined parameters (5 factors), which highlighted the advantages of this innovative optimization technique. The result shows that the optimal formula for producing a djulis sourdough bread with the best texture, color, and sensory qualities was A3B1C1D2E2, i.e., 20% djulis sourdough, 0% addition of hulled djulis, 8% unsalted butter, 80% wheat flour + 20% high-gluten flour, and 10% honey, respectively. Such a novel application could be a reference for improving the quality of bakery products in the industry. Moreover, it seems that the new bakery product developed in this study has good potential to be commercially produced after further nutritional and economic analysis.

Storage stability and sourdough acidification kinetic of freeze-dried Lactobacillus curvatus N19 under optimized cryoprotectant formulation

In this study, the response surface methodology was used to optimize the cryoprotective agent (skimmed milk powder, lactose and sucrose) formulation for enhancing the viability of Lactobacillus curvatus N19 during freeze-drying and storage stability of cells freeze-dried by using optimum formulation was evaluated. Our results showed that the most significant cryoprotective agent influencing the viability of L. curvatus N19 to freezing and freeze-drying was sucrose and skim milk, respectively. The optimal formulation of cryoprotective agents was 20 g/100 mL skim milk, 3.57 g/100 mL lactose and 10 g/100 mL sucrose. Using the optimum formulation during freeze-drying, the cell survival was found more than 98%. Under the optimal conditions, although only storage of the cells at 4 °C for 6 month retained the maximum stability (8.85 log cfu/g), the employed protectant matrix showed promising results at 25 °C (7.89 log cfu/g). The storage stability of cells under optimized conditions was predicted by accelerated storage test, which was demonstrated that the inactivation rate constant of the freeze-dried L. curvatus N19 powder was 9.74 × 10^-6 1/d for 4 °C and 2.08 × 10^-3 1/d for 25 °C. The loss of specific acidification activity after the storage at 4 and 25 °C was determined.

Transformations of Selected Fusarium Toxins and Their Modified Forms During Malt Loaf Production

An increasing number of studies have found that modified mycotoxins, such as free mycotoxins, naturally occur in food, and severely impact food safety. The present study investigated concentrations of trichothecenes nivalenol (NIV), deoxynivalenol (DON), and zearalenone (ZEN), together with their modified forms, nivalenol-3-glucoside (NIV-3G), deoxynivalenol-3-glucoside (DON-3G), and zearalenone-14-glucoside (ZEN-14G) and zearalenone-14-sulfate (ZEN-14S), respectively, at successive stages of malt loaf production (flour, dough kneading/fermentation, loaf baking). Toxins in bakery products originate in flour produced from wheat grain that is naturally contaminated with Fusarium culmorum. Mycotoxin concentrations were determined using high-performance liquid chromatography-high resolution mass spectrometry, and did not significantly change during the successive stages of bread production. After the dough kneading/fermentation stage, concentrations of NIV-3G and DON-3G were slightly increased, whereas those of ZEN and ZEN-14S were slightly decreased. The largest average decrease (21%) was found in ZEN-14G. After the baking stage, the average concentrations of NIV-3G, DON-3G, ZEN-14S, and ZEN-14G in the loaf crumb and crust decreased by 23%, 28%, 27%, and 20%, respectively, compared with those in the dough. During this technical process, the concentration of ZEN-14G in loaf crumb significantly decreased by an average of 48%, and those of ZEN, ZEN-14S, and ZEN-14G in loaf crust decreased by an average of 29%, 42%, and 48%, respectively. Considering the possibility of modified mycotoxins degradation to free forms, as well as the ability to synthesize them from free forms during technological processes, it would be prudent to consider them together during analysis.

The Inhibition of Amylase and ACE Enzyme and the Reduction of Immunoreactivity of Sourdough Bread

This study examines the potential health benefits of different types of wheat sourdough bread against diseases of civilization. Celiac disease, diabetes and hypertension affect large numbers of the world's population, increasing demand for novel treatments and ways of improving patient welfare. Different types of artisan breads were subjected to in vitro simulated digestion prior to analysis. The G12 test and ELISA with human sera were used for immunoreactivity analysis. The activity of α-amylase inhibitors and angiotensin-converting enzymes (ACE) was also assessed. The addition of sourdough to the analyzed wheat bread raised the content of α-amylase inhibitors and angiotensin-converting enzyme inhibitors while reducing their immunoreactivity. However, despite decreases in the antigenicity of the wheat flour proteins, the sera showed various reactions, depending on the individual patient's susceptibility to gluten.

Preliminary Survey of Alternaria Toxins Reduction during Fermentation of Whole Wheat Dough

The aim of this study was to investigate the fate of the most common Alternaria toxins found in wheat-tenuazonic acid (TeA), alternariol (AOH), and alternariol monomethyl ether (AME) during sourdough processing. For this purpose, spiked whole wheat flour, 3% sourdough starter, 0.5% of baker's yeast, and 105% of water calculated on flour weight as a base were used as raw materials. Spiked whole wheat dough was fermented for 4 h, 8 h, 12 h, 24 h, and 48 h at 25 °C, and at each point the fermented dough samples were taken, frozen, lyophilized, grounded, and stored until further analysis. To study the effect of sourdough processing on TeA, AOH and AME content, the validated method of high-performance liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) for these mycotoxins was used. Mathematical models of Alternaria toxins reduction were developed in the form of Four Parameter Logistic Regression function. The maximum reduction of TeA, AOH, and AME levels was archived at 48 h of dough fermentation at 25 °C compared with dough after kneading (0 h). Under these conditions, a reduction of the toxin levels of 60.3 %, 41.5%, and 24.1% was observed for TeA, AOH, and AME, respectively.

Flaxseed Cake as a Tool for the Improvement of Nutraceutical and Sensorial Features of Sourdough Bread

Flaxseed has been recently studied for the formulation of healthy functional foods that are also useful for the prevention of chronic diseases. In this context, the production of sourdough bread fortified with different percentages of flaxseed cake was performed and the interactions among the bioactive compounds derived from both sourdough and flaxseed cake were investigated. The organoleptic properties as well as nutraceutical and chemical characteristics regarding pH, ethanol, lactic and acetic acid content, fatty acids profile, the concentration of total polyphenols, antioxidant capacity, and aroma volatile organic compounds were determined to evaluate the efficacy of leavening in the different matrices in comparison with the traditional bread. The results obtained demonstrated that flaxseed cake-enriched sourdough bread can represent a potential vehicle for bioactive compounds with the possibility of obtaining high-quality products with improved nutritional profiles and desired health attributes. Furthermore, the bread obtained with the addition of 7.5% of flaxseed cake was individuated as the best formulation to produce sourdough bread fortified with flaxseed cake by the overlap between three series of information coming from physical-chemical, nutritional, and sensorial analyses. In conclusion, in the operating conditions adopted, the use of flaxseed cake could represent a viable alternative for the production of fortified bread based on sourdough technology.

From Microbial Ecology to Innovative Applications in Food Quality Improvements: the Case of Sourdough as a Model Matrix

Since millennia, humankind has exploited microbial diversity associated to give food matrices in order to obtain fermented foods and beverages, resulting in products with improved quality and extended shelf life. This topic has received deserved and continuous interest in the scientific community, for the reason of its significance as a driver of innovation in the food and beverage sector. In this review paper, using sourdough as a model matrix, we provide some insights into the field, testifying the relevance as a transdisciplinary subject. Firstly, we encompassed the prokaryotic and eukaryotic microbial diversity associated with the sourdough ecosystems. The importance of this micro-biodiversity in the light of flour-related chemical diversity was examined. Finally, we highlighted the increasing interest in microbial-based applications oriented toward biocontrol solution in the field of sourdough-based products (i.e., bread).

Development of new microalgae-based sourdough "crostini": functional effects of Arthrospira platensis (spirulina) addition

The aim of this work was to evaluate the influence of Arthrospira platensis F&M-C256 (spirulina) incorporation on the nutritional and functional properties of "crostini", a leavened bakery product largely consumed in Italy and Europe. Sourdough was used as leavening and fermentation agent and three concentrations of A. platensis F&M-C256 were tested: 2%, 6% and 10% (w/w). Despite a lower volume increase compared to the control, the A. platensis F&M-C256 "crostini" doughs reached a technological appropriate volume after fermentation. At the end of fermentation, no significant differences in microorganisms concentrations were observed. A. platensis F&M-C256 "crostini" showed higher protein content compared to the control. Considering the European Commission Regulation on nutritional claims, "crostini" incorporated with 6% and 10% biomass can be claimed to be a "source of protein". Six and ten percent A. platensis "crostini" also presented significantly higher antioxidant capacity and phenolics. A significantly lower value of in vitro dry matter and protein digestibility between A. platensis F&M-C256 "crostini" and the control was found. The overall acceptability decreased with increasing A. platensis F&M-C256 addition. The combination of spirulina biomass addition and the sourdough technology led to the development of a novel microalgae-based bakery product with nutritional and functional features.

A Study of Structural Change During In Vitro Digestion of Heated Soy Protein Isolates

Use of soy protein isolate (SPI) as the encapsulating material in emulsions is uncommon due to its low solubility and emulsification potential. The aim of this study was to improve these properties of SPI via heat treatment-induced modifications. We modified SPI under various heating conditions and demonstrated the relationship between structure and in vitro digestibility in simulated gastric fluid by means of Sodium Dodecyl Sulphide-Polyacrylamide Gel Electrophoresis (SDS-PAGE) and Raman spectroscopy. It was found that the degree of hydrolysis (DH) of SPI increased and then decreased upon increasing exposure to heat. Different subunits of conglycinin were digested and degraded by pepsin. Heat treatment improved digestion characteristics that would reduce e the unnecessary loss of protein, offering potential for the efficient delivery of nutrients in nanoemulsions. These results could have significant relevance for research groups that are interested in the biological interactions and activity of functional SPI.

Optimisation of important processing conditions for rice bran sourdough fermentation using Lactobacillus plantarum

The potentials of rice bran sourdough in bread making are recently gaining popularity. However, there is no information on the influence of processing conditions on the quality attributes of rice bran sourdough. To inves- tigate the influence of fermentation time and temperature on the levels of acidity (pH and TTA) in rice bran sour- dough fermented with L. plantarum, we applied response surface methodology (RSM). Furthermore, we studied the effect of different fermentation time and temperature on the total phenolic and volatile compounds in the sourdough. GC/MS measurements for the evolution of aroma volatile compounds (VOCs) in the rice bran sourdoughs were conducted. The higher and longer the fermentation temperature and time, the higher the acidity levels in the sour- doughs. Fermentation temperature and time do not have a significant effect on the total phenolic sourdough con- tents. Forty-seven VOCs were detected in the rice bran sourdoughs. The major VOCs were acetic acids, ethanol, 2-Methoxy-4-vinylphenol, Hexadecanoic acid, 1-(hydroxymethyl)-1,2-ethanediyl ester, acetoin, and 2-methoxy-Phe- nol. The sourdough fermented at 35°C for 13 ho contained the largest number (27) of aroma compounds and had the highest acidity. These fermentation conditions are close to the optimal parameters (temperature – 33°C, duration – 12.5 hours), obtained as a result of applying RSM for rice bran fermentation. Thus, high quality bran sourdough can be produced at the temperature of 33°C for 12.5 hours. The results of this study will be useful to produce a quality rice bran sourdough bread with appealing aroma and a long shelf-life.

Comparison of bacterial communities in gliadin-degraded sourdough (Khamir) sample and non-degraded sample

The study was undertaken to investigate the comparison lying between bacterial communities in autochthonous gliadin-degraded sourdough sample (D13) and non-degraded sample (D50). Degree of gliadin degradation in various samples was determined by Fourier transform infrared spectroscopy and represented samples were selected for 16 S rDNA sequence analysis by Illumina Miseq platform. It was observed, that Proteobacteria (50.65%) and Actinobacteria (6.70%) phyla were more abundant as compared with Firmicutes (42.53%) in D13, however, Firmicutes (83.44) were more abundant, comparatively, in D50 than Proteobacteria (14.97%). Lower taxonomic levels surfaced its more prominent effects. It had been also observed that Lactobacillus genera was the core genera (50.37%) followed by Weissella (27.15%) and Psychrobacter (21.53%) in D50 and D13, respectively. Shannon and Simpson indices indicated that degraded sample had more bacterial diversity and richness compared with non-degraded sample.

Defined co-cultures of yeast and bacteria modify the aroma, crumb and sensory properties of bread

AIMS

Yeast and bacterial communities inhabit a sourdough starter to make artisanal bread. This study shows whether the interactions of micro-organisms derived from Australian sourdough starters provide some of the positive flavour, and aroma properties to bread by using defined sourdough cultures as the sole leaven in bread production.

METHODS AND RESULTS

An investigation of Australian sourdough starters found that they contained Saccharomyces cerevisiae and Kazachstania exigua yeasts. When these yeasts were inoculated alone to ferment wheat flour in an extended fermentation, the bread had a heterogeneous crumb structure, a deeper colour and a distinctive chemical aroma profile than those made with commercial baker's yeast. When bread was made combining these yeasts individually and in combinations with lactic acid bacteria also isolated from these sourdough starters, including Lactobacillus plantarum, L. brevis, L. rossiae, L. casei, the bread aroma profiles and crumb structure were more distinctive, with compounds associated with sour aromas produced, and preferred by sensory panels.

CONCLUSIONS

The use of defined mixed cultures as the leaven in bread making, by exploiting the microbial diversity of artisanal Australian starters, can produce bread with distinctive and attractive aromas.

SIGNIFICANCE AND IMPACT OF THE STUDY

Understanding and identifying the community ecosystems found in sourdough cultures and using them as the sole leaven in bread production provide novel insights into microbial interactions and how they affect food quality by removing the effects of commercial yeast strains.

Lactic Fermentation as a Strategy to Improve the Nutritional and Functional Values of Pseudocereals

One of the greatest challenges is to reduce malnutrition worldwide while promoting sustainable agricultural and food systems. This is a daunting task due to the constant growth of the population and the increasing demands by consumers for functional foods with higher nutritional values. Cereal grains are the most important dietary energy source globally; wheat, rice, and maize currently provide about half of the dietary energy source of humankind. In addition, the increase of celiac patients worldwide has motivated the development of gluten-free foods using alternative flour types to wheat such as rice, corn, cassava, soybean, and pseudocereals (amaranth, quinoa, and buckwheat). Amaranth and quinoa have been cultivated since ancient times and were two of the major crops of the Pre-Colombian cultures in Latin- America. In recent years and due to their well-known high nutritional value and potential health benefits, these pseudocereals have received much attention as ideal candidates for gluten-free products. The importance of exploiting these grains for the elaboration of healthy and nutritious foods has forced food producers to develop novel adequate strategies for their processing. Fermentation is one of the most antique and economical methods of producing and preserving foods and can be easily employed for cereal processing. The nutritional and functional quality of pseudocereals can be improved by fermentation using Lactic Acid Bacteria (LAB). This review provides an overview on pseudocereal fermentation by LAB emphasizing the capacity of these bacteria to decrease antinutritional factors such as phytic acid, increase the functional value of phytochemicals such as phenolic compounds, and produce nutritional ingredients such as B-group vitamins. The numerous beneficial effects of lactic fermentation of pseudocereals can be exploited to design novel and healthier foods or grain ingredients destined to general population and especially to patients with coeliac disease.

Increasing the fermentation efficiency of Lactobacillus paracasei ssp. paracasei MIUG BL6 in a rye flour sourdough

Background

The present study reports the optimization of the biotechnological conditions in order to improve the lactic acid fermentation process, in a rye flour medium by using Lactobacillus paracasei ssp. paracasei strain, coded MIUG BL6, as a starter culture.

Materials and methods

A sequential statistical methodology, comprised of Plackett-Burman experimental design, central composite design and response surface methodology, was applied to enhance the lactic acid fermentation productivity.

Results and discussion

Among the tested parameters, the milk powder and KH2PO4 concentration and also the time of fermentation were identified as the most significant variables that influence the fermentation process. The optimum levels of these significant parameters were determined as follows: 4.21% milk powder, 0.30% KH2PO4 and 48 h of fermentation that induced an increase of 1.6 fold of the acidity, compared to the fermentation conducted under the non-optimized conditions. Also, under these optimized fermentation conditions, a good rate of cell multiplication of 10.19 log N/N0 was achieved.

Application of antifungal lactobacilli in combination with coatings based on apple processing by-products as a bio-preservative in wheat bread production

In this study various coatings from apple press cake (AP) with immobilized antifungal bacterial cells were used for bread surface treatment to increase anti-moulding effect. The antifungal effect and technological properties of newly isolated Lactobacillus coryniformis LUHS71, L. curvatus LUHS51, L. farraginis LUHS206 and Leuconostoc mesenteroides LUHS225 strains. Then, the lactobacilli were tested for the effects of incorporation of sourdough on acrylamide formation in bread and antifungal effect against moulds commonly associated with bread spoilage. The addition of 15-20% of sourdoughs significantly (p = 0.0001) improved bread volume and crumb porosity depending on LAB strain, and reduced acrylamide formation on average by 23% (for LUHS51 and LUHS206) by 54% (for LUHS71 and LUHS225) compared to control bread. Additionally, the use of AP-LAB coatings prolonged shelf life from 3 to 6 days for control bread, and up to 9 days for sourdough breads. The combination of antifungal LAB sourdough and the AP-LAB coating leads to produce high quality bread with extended shelf life and would be a new and promising environmentally-friendly technological alternative.

Recent Advances in the Use of Sourdough Biotechnology in Pasta Making

The growing consumers’ request for foods with well-balanced nutritional profile and functional properties promotes research on innovation in pasta making. As a staple food and a common component of diet, pasta can be considered as a vector of dietary fiber, vegetable proteins, vitamins, minerals, and functional compounds. The conventional process for pasta production does not include a fermentation step. However, novel recipes including sourdough-fermented ingredients have been recently proposed, aiming at enhancing the nutritional and functional properties of this product and at enriching commercial offerings with products with new sensorial profiles. The use of sourdough for pasta fortification has been investigated under several aspects, including fortification in vitamin B, the reduction of starch digestibility, and gluten content. Sourdough fermentation has also been successfully applied to non-conventional flours, (e.g., from pseudocereals and legumes), in which an overall increase of the nutritional value and health-promoting compounds, such as a significant decrease of antinutritional factors, were observed. Fermented non-conventional flours, obtained through spontaneous fermentation or using selected starters, have been proposed as pasta ingredients. As the result of wheat replacement, modification in textural properties of pasta may occur. Nonetheless, fermentation represents an efficient tool in improving, besides nutritional and functional profile, the sensory and technological features of fortified pasta.

Use of a Selected Leuconostoc Citreum Strain as a Starter for Making a "Yeast-Free" Bread

The aim of this study was the characterization and selection of bacterial strains suitable for the production of a “yeast-free” bread. The strains Leuconostoc citreum C2.27 and Weissella confusa C5.7 were selected for their leavening and acidification capabilities and individually used as starters in bread-making tests. Liquid type-II sourdoughs, singly inoculated with the two selected strains, were characterized and employed for bread-making, through the set-up of a biotechnological protocol without the use of baker’s yeast as a leavening agent. Aiming to verify the ability of the selected strains to dominate the fermentation process, bacteria and yeasts were isolated from liquid sourdoughs and doughs, genetically characterized and identified. Both the selected strains were suitable for the production of bread, even if L. citreum C2.27 showed the highest leavening capacity and was able to dominate the dough microbiota. The effects of different salt concentrations on the selected strain performances were also investigated. The applicability of the developed protocol, adapted for the production of the typical Apulian bread, “puccia”, and the suitability of the strain L. citreum C2.27 were confirmed at pilot scale in an industrial bakery. The puccia bread, which was produced with the liquid sourdough fermented with L. citreum C2.27, without baker’s yeast and salt, was similar in appearance to the conventional product containing baker’s yeast and was judged positively by a sensory analysis.