Influence of Process Parameters on Sourdough Microbiota, Physical Properties and Sensory Profile

The impact of fermentation length and dough composition on the stability of liquid sourdough starters

Sourdough breadmaking on an industrial scale requires robust, well-performing starters that bring attractive characteristics to the product. The active nature of liquid starters provides a faster fermentation process compared to their dehydrated counterparts. However, liquid sourdough starters require meticulous management in order to maintain stability and functionality during cold storage at 4 °C. This study investigated the stability of three liquid sourdough starters during storage and also the impact of prolonged fermentation, the addition of diastatic malted wheat flour, and a neutralising agent (CaCO3). The sourdough starters were evaluated for their microbial viability and metabolic activity at three individual time points during 16 weeks of cold storage. The microbial composition was analysed using culture-dependent and culture-independent methods, and metabolic changes were investigated using chromatographic methods. Two types of sourdough starter showed satisfying viability of lactic acid bacteria (> 7 log CFU/g) and metabolic stability throughout 16 weeks of cold storage. The introduction of malted wheat flour and CaCO3 caused a decline in viability to <7 log CFU/g within 8 weeks in the third sourdough starter type and additionally revealed an ongoing metabolic activity of this sourdough starter during cold storage. Prolonged fermentation influenced the free amino acid profile, whereas adjusting the sourdough starter formula resulted in a different fungal microbiota and increased levels of fermentable substrates (maltose), organic acids (lactic acid), and aromatic compounds (alcohol and aldehydes). These findings provide stakeholders and researchers in sourdough fermentation technology with new insights concerning the stability of cold-stored liquid sourdough starters.

Novel Formulations of Sourdough Bread Based on Supplements Containing Chokeberry Juice Fermented by Potentially Probiotic L. paracasei SP5

The current study focused on sourdough breads produced with various supplements consisting of freeze-dried black chokeberry juice, (i) unfermented and (ii) fermented by Lactiplantibacillus paracasei SP5, aiming to enhance their functionality and nutritional value. Specifically, the impact of these supplements on the quality of sourdough breads was evaluated in terms of their nutritional features, antimicrobial capacity, and sensorial characteristics. Sourdough breads produced with freeze-dried fermented chokeberry juice exhibited elevated concentrations of lactic acid (2.82-2.99 g/kg) and acetic acid (0.93-0.99 g/kg), which significantly prolonged their resistance to mould growth and rope contamination, maintaining freshness for over 13 days. These samples also demonstrated higher antioxidant activity, with DPPH values exceeding 4 μmol TE/g and ABTS values surpassing 218 mg TE/100 g, along with a total phenolic content ranging from 85.9 to 96.3 mg GAE/100 g. Additionally, these samples showed a greater reduction in phytate, an antinutrient, compared to all other samples, including the control. The sensory evaluation conducted with consumer panels indicated that sourdough breads prepared with freeze-dried fermented chokeberry juice achieved the highest ratings in terms of taste and appearance among all tested samples. The findings are highly promising and suggest the potential for commercializing the developed supplements in the production of additive-free sourdough bread with enhanced nutritional value.

Application of selected lactic acid bacteria isolates for bread production without baker's yeast

The isolates of lactic acid bacteria (LAB) from traditional fermented koumiss and homemade dry rye sourdough were examined for their potential to be used in bread production without baker's yeast. Among twenty isolates, three with superior fermentation ability and acidification capability were identified by 16S rRNA gene sequencing. Leuconostoc mesenteroides from koumiss, Levilactobacillus brevis from 48 h activated rye sourdough, and Leuconostoc citreum from rye sourdough extract were singly and mixed (1:1:1) inoculated into liquid sourdoughs and used for bread-making tests. Bread prepared with Saccharomyces cerevisiae was used as the control. The substitution of water with whey in LAB fermentation demonstrated lower pH and higher total titratable acidity values in the sourdough. The resulting bread's color parameters, textural properties, and sensory characteristics confirmed the suitability of the selected strains to produce bread without baker's yeast and highlighted the enhancement of new starter varieties.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-024-01571-7.

Genotypic Stability of Lactic Acid Bacteria in Industrial Rye Bread Sourdoughs Assessed by ITS-PCR Analysis

Sourdough bread production relies on metabolically active starters refreshed daily with flour and water. The stability of sourdough microbial strains is crucial for consistent bread quality. However, many bakeries lack information on the persistence of starter cultures in ongoing sourdough production. Consequently, there is growing interest in identifying microbial strains from regularly used sourdoughs that possess good functional properties and resist changes in the complex growth environment. This study aimed to evaluate the composition and stability of lactic acid bacteria (LAB) in industrial wheat (WS) and rye (RS) sourdoughs propagated over a long period. LAB isolates (n = 66) from both sourdoughs, sampled over four seasons, were identified using phenotypic methods and genotyped via ITS-PCR and ITS-PCR/TaqI restriction analysis. Eight LAB species were detected, with Lactiplantibacillus plantarum being the most dominant and stable. Nineteen distinct LAB genotypes were observed, highlighting significant diversity. The presence of identical LAB genotypes in both sourdoughs suggests microbial transfer through the environment and bakery workers. LAB in RS were found to be more stable than those in WS. These findings underscore the importance of monitoring microbial stability and diversity in industrial sourdough production to maintain consistent bread quality.

Optimizing Lactic Acid Bacteria Proportions in Sourdough to Enhance Antifungal Activity and Quality of Partially and Fully Baked Bread

The organic acids produced by lactic acid bacteria (LAB) during the fermentation of sourdoughs have the ability to reduce the growth of different molds. However, this ability depends on the LAB used. For this reason, in this study, the proportions of different LAB were optimized to obtain aqueous extracts (AEs) from sourdough to reduce fungal growth in vitro, control the acetic acid concentration, and obtain a specific lactic to acetic acid ratio. In addition, the optimized mixtures were used to formulate partially baked bread (PBB) and evaluate the mold growth and bread quality during refrigerated storage. Using a simplex-lattice mixture design, various combinations of Lactiplantibacillus plantarum, Lacticaseibacillus casei, and Lactobacillus acidophilus were evaluated for their ability to produce organic acids and inhibit mold growth. The mixture containing only Lpb. plantarum significantly reduced the growth rates and extended the lag time of Penicillium chrysogenum and P. corylophilum compared with the control. The AEs' pH values ranged from 3.50 to 3.04. Organic acid analysis revealed that using Lpb. plantarum yielded higher acetic acid concentrations than when using mixed LAB. This suggests that LAB-specific interactions significantly influence organic acid production during fermentation. The reduced radial growth rates and extended lag times for both molds compared to the control confirmed the antifungal properties of the AEs from the sourdoughs. Statistical analyses of the mixture design using polynomial models demonstrated a good fit for the analyzed responses. Two optimized LAB mixtures were identified that maximized mold lag time, targeted the desired acetic acid concentration, and balanced the lactic to acetic acid ratio. The addition of sourdough with optimized LAB mixtures to PBB resulted in a longer shelf life (21 days) and adequately maintained product quality characteristics during storage. PBB was subjected to complete baking and sensory evaluation. The overall acceptability was slightly higher in the control without sourdough (7.50), followed by bread formulated with the optimized sourdoughs (ranging from 6.78 to 7.10), but the difference was not statistically significant (p > 0.05). The sensory analysis results indicated that the optimization was used to successfully formulate a sourdough bread with a sensory profile closely resembling that of a nonsupplemented one. The designed LAB mixtures can effectively enhance sourdough bread's antifungal properties and quality, providing a promising approach for extending bread shelf life while maintaining desirable sensory attributes.

Sourdough Bread Quality: Facts and Factors

The term "sourdough" denotes a dough composed of flour and water, fermented through the action of yeast and lactic acid bacteria. The utilization of sourdough fermentation technology can enhance the nutritional attributes of bread made from wheat grain. In recent times, sourdough bread has experienced a resurgence, fueled by growing consumer demand for healthier bread options. The market dynamics for sourdough illustrate its rapid expansion and significant role in the contemporary food industry. Sourdough fermentation improves nutritional qualities by altering the structure and function of proteins and starch, enhancing dietary fiber, volatile compound profiles, and antioxidant activity, and reducing FODMAPs. The quality of sourdough bread is influenced by several factors, including fermentation environment, flour particle size, protein quality, starch characteristics, and dietary fiber composition. Moreover, the incorporation of alternative grains (intermediate wheatgrass and legume flour) and non-flour ingredients (fruits, herbs, and dairy products) presents opportunities for creating sourdough bread with unique sensory and nutritional profiles. This review offers updated insights on the quality aspects of sourdough fermentation, the factors that influence the effectiveness of the sourdough fermentation process, sourdough technology with unconventional and non-flour ingredients, and the potential market for frozen sourdough, considering its convenience and extended shelf life.

Monitoring the Dough Properties, Quality Characteristics and Volatile Compounds of Whole Wheat Bread Made by Different Sourdough Types during Frozen Storage

There is a need to increase the consumption of whole wheat bread (WWB) due to its health benefits by overcoming its poor technological quality and improving its sensory characteristics. In this study, sourdough bread-making and frozen dough technology were combined to provide fresh WWB at any time with better quality. Also, it was aimed to investigate the effects of three types of sourdough (type I, II, and IV) on the final quality of WWB during frozen storage (-30 °C, 14 and 28 days). The tan δ of WWB with type I sourdough was highest at the end of the frozen storage. Freezable water content was lower on day 0 for WWB with type II and IV sourdough than other bread types. No significant effect of frozen storage was observed in bread types in terms of an α helix structure, except for WWB with type I sourdough. A lower hardness increment was shown in WWB with baker's yeast and WWB with type II sourdough over 14 days of frozen storage when compared to other bread types. WWB with type I sourdough and WWB with type IV sourdough were differentiated from other bread samples in volatile compound (VC) analysis on frozen storage days 28 and 0, respectively. The frozen storage of WWB with baker's yeast and WWB with type II sourdough caused no notable changes in the VCs profile. These results suggest that a less detrimental effect of frozen storage was observed in WWB with type II sourdough, indicating a more favorable choice for producing WWB with sourdough.

A review of the effects of fermentation on the structure, properties, and application of cereal starch in foods

Fermentation is one of the oldest food processing techniques known to humans and cereal fermentation is still widely used to create many types of foods and beverages. Starch is a major component of cereals and the changes in its structure and function during fermentation are of great importance for scientific research and industrial applications. This review summarizes the preparation of fermented cereals and the effects of fermentation on the structure, properties, and application of cereal starch in foods. The most important factors influencing cereal fermentation are pretreatment, starter culture, and fermentation conditions. Fermentation preferentially hydrolyzes the amorphous regions of starch and fermented starches have a coarser appearance and a smaller molecular weight. In addition, fermentation increases the starch gelatinization temperature and enthalpy and reduces the setback viscosity. This means that fermentation leads to a more stable and retrogradation-resistant structure, which could expand its application in products prone to staling during storage. Furthermore, fermented cereals have potential health benefits. This review may have important implications for the modulation of the quality and nutritional value of starch-based foods through fermentation.

Role of tailored sourdough fermentation in the flavor of wholegrain-oat bread

Sourdough technology has been known for its role in the improvement of texture, flavor, and quality of mainly wheat and rye-based breads for decades. However, little is reported about its use in the improvement of whole-grain oat bread, especially concerning flavor formation, which is one major consumer drivers. This study investigated the effects of sourdough obtained by different lactic acid bacteria and yeast starters consortia on the texture and flavor of 100% oat bread. Four different consortia were selected to obtain four oat sourdoughs, which were analyzed to assess the main features due to the different starter fermentation metabolism. Sourdoughs were added to breads as 30% dough weight. Bread quality was technologically monitored via hardness and volume measurements. Sourdough breads were softer and had higher specific volume. The sensory profile of sourdoughs and breads was assessed by a trained panel in sensory laboratory conditions, and the volatile profile was analyzed by HS-SPME-GC-MS. Sourdoughs were rated with higher intensities than untreated control for most of attributes, especially concerning sour aroma and flavor attributes. Sourdough breads were rated with higher intensities than control bread for sour vinegar flavor and total odor intensity, in addition they had richer volatile profile. Our results confirmed that sourdough addition can lead to an enhanced flavor, moreover, it demonstrated that the use of different consortia of lactic acid bacteria and yeast strains leads to the improvement of texture and altered sensory profile of whole-oat bread.

Nutritional and sensory quality of Ofada rice sourdough bread made with selected lactic acid bacteria strains

Celiac disease ranks highest among immunological disorders attributed to gluten consumption thus, posing great demands on gluten-free products. Rice is a gluten-free cereal with promising dietary applications. Ofada rice, a native southwestern Nigerian variety, can be improved with sourdough technology to develop functional aglutenic bread. Ofada rice sourdough bread (ORSB) was made with Fructilactobacillus fructivorans RY1, Weissella viridescens RY9 and Lactobacillus acidophilus RY10 as individual and combined starter cultures. Physical qualities, proximate contents, sensorial attributes and shelf-life of the ORSBs were evaluated. Sourdough bread with the highest (3.10 cm3/g) and lowest specific volumes (2.02 cm3/g) were the sample made single culture of W. viridescens and F. fructivorans, respectively. The highest crude protein (8.48 %) was found in ORSB with only F. fructivorans and ORSB with L. acidophilus singly had the highest content (0.44 %) of crude fibre. Nevertheless, the least crude protein (5.25 %) and crude fibre (0.28 %) were observed in samples containing F. fructivorans, W. viridescens, and L. acidophilus as combined starters. The sourdough bread with F. fructivorans as a starter scored best for texture and overall acceptability. The ORSBs had shelf-life ranging from three to four days. It was revealed in the study that using the specific LAB starters could improve the physicochemical attributes and acceptability of bread from Ofada rice flour.

Challenges and perspectives of quantitative microbiome profiling in food fermentations

Spontaneously fermented foods are consumed and appreciated for thousands of years although they are usually produced with fluctuated productivity and quality, potentially threatening both food safety and food security. To guarantee consistent fermentation productivity and quality, it is essential to control the complex microbiota, the most crucial factor in food fermentations. The prerequisite for the control is to comprehensively understand the structure and function of the microbiota. How to quantify the actual microbiota is of paramount importance. Among various microbial quantitative methods evolved, quantitative microbiome profiling, namely to quantify all microbial taxa by absolute abundance, is the best method to understand the complex microbiota, although it is still at its pioneering stage for food fermentations. Here, we provide an overview of microbial quantitative methods, including the development from conventional methods to the advanced quantitative microbiome profiling, and the application examples of these methods. Moreover, we address potential challenges and perspectives of quantitative microbiome profiling methods, as well as future research needs for the ultimate goal of rational and optimal control of microbiota in spontaneous food fermentations. Our review can serve as reference for the traditional food fermentation sector for stable fermentation productivity, quality and safety.

Quality Characteristics of Novel Sourdough Breads Made with Functional Lacticaseibacillus paracasei SP5 and Prebiotic Food Matrices

Lacticaseibacillus paracasei SP5, isolated from kefir, was assessed as a starter culture for sourdough bread making in freeze-dried form, both free (BSP5 bread) and immobilised on wheat bran (BIWB) and on a traditional flour/sour milk food, ‘trahanas’ (BITR). Physicochemical characteristics, shelf-life, volatilome, phytic acid, and sensory properties of the breads were evaluated. The BITR breads had higher acidity (9.05 ± 0.14 mL of 0.1 M NaOH/10 g) and organic acid content (g/Kg; 2.90 ± 0.05 lactic, 1.04 ± 0.02 acetic), which justifies the better resistance against mould and rope spoilage (>10 days). The highest number of volatiles (35) and at higher concentration (11.14 μg/g) were also found in BITR, which is in line with the sensory (consumer) evaluation regarding flavour. Finally, higher reduction of phytate (an antinutrient) was observed in all L. paracasei SP5 sourdoughs (83.3–90.7%) compared to the control samples (71.4%). The results support the use of the new strain for good quality sourdough bread.

Changes in the Volatile Profile of Wheat Sourdough Produced with the Addition of Cava Lees

The volatile fraction is of great importance for the organoleptic quality and consumer acceptance of bread. The use of sourdough improves the sensory profile of bread, as well as the addition of new ingredients to the fermentation. Cava lees are a sparkling wine by-product formed of dead microorganisms, tartaric acid, and other inorganic compounds, rich in antioxidant compounds as well as β-glucans and mannoproteins. The aim of this study was to evaluate the effect of different concentrations of Cava lees (0–2% w/w) on sourdough volatile compounds to re-valorize this by-product of the wine industry. Headspace solid-phase microextraction (HS-SPME) was optimized to study the volatile fractions of sourdoughs. The parameters selected were 60 °C, 15 min of equilibrium, and 30 min of extraction. It was found that the addition of Cava lees resulted in higher concentrations of volatile compounds (alcohols, acids, aldehydes, ketones and esters), with the highest values being reached with the 2% Cava lees. Moreover, Cava lees contributed to aroma due to the compounds usually found in sparkling wine, such as 1-butanol, octanoic acid, benzaldehyde and ethyl hexanoate.

By-Product Revalorization: Cava Lees Can Improve the Fermentation Process and Change the Volatile Profile of Bread

Wine lees are a by-product that represents a 25% of the total winery waste. Although lees are rich in antioxidant compounds and dietary fiber, they have no added value and are considered a residue. The aim of this study was to evaluate the effect of Cava lees (0 and 5% w/w) on microbial populations during sourdough and bread fermentation and the volatile fraction of the final bread. The results showed that 5% Cava lees promoted the growth of both lactic acid bacteria (LAB) and yeast in short fermentations (bread) but did not improve microbial growth in long fermentations (sourdough). Regarding volatile compounds, the addition of Cava lees increased the concentration of volatiles typically found in those products. Also, some compounds reported in sparkling wines were also identified in samples with Cava lees adsorbed on their surface. To sum up, the addition of Cava lees to sourdough and, especially, bread formulation may be a new strategy to revalorize such by-product.

Revalorization of Cava (Spanish Sparkling Wine) Lees on Sourdough Fermentation

Cava lees are a sparkling wine by-product formed of dead microorganisms, tartaric acid and other inorganic compounds, with a potential for enhancing microbial growth. Lees are rich in antioxidant compounds as well as β-glucans and mannoproteins. The aim of this study was to evaluate the effect of different concentrations of cava lees (0–2% w/w) on the microbiota (LAB and yeasts) responsible for sourdough fermentation (8 days) to revalorize this by-product of the wine industry. The results showed that 2% cava lees promoted microbial growth and survival in both wheat and rye sourdoughs, except for yeast growth in rye, which stopped at day 3 of fermentation. Moreover, sourdough with lees achieved lower pH values as well as higher concentrations of organic acids, especially lactic and acetic acids (p < 0.05). To sum up, the use of cava lees in sourdough formulation promotes the growth and survival of microorganisms, which, in consequence, promotes a lower pH and greater amounts of organic acids. This could lead to microbial stability as well as changes in bread flavor.