The production of esters by specific sourdough lactic acid bacteria species is limited by the precursor concentrations

The production of fruity esters by sourdough lactic acid bacteria (LAB) and yeasts has not been explored in detail. Moreover, the biosynthesis of esters by LAB species under conditions similar to those occurring during sourdough production is still questionable. Concerning yeasts, a genome mining of 75 genomes revealed a strain dependency of the presence of seven specific ester biosynthesis genes. Accordingly, PCR assays to detect these acetate (ATF1 and ATF2) and ethyl ester (EHT1 and EEB1) biosynthesis genes were developed and used to screen 91 strains of yeast species. Concerning LAB, a genome mining of 401 genomes revealed a species dependency of the presence of three esterase-encoding genes (estA, estB, and estC). A phenotypic analysis carried out with a selection of 10 strains of the LAB species Companilactobacillus crustorum, Companilactobacillus nantensis, Companilactobacillus paralimentarius, Fructilactobacillus sanfranciscensis, Lactiplantibacillus xiangfangensis, Levilactobacillus zymae, and Limosilactobacillus fermentum in a wheat sourdough simulation medium (WSSM) supplemented with ester precursor molecules ([higher] alcohols and fatty acids) revealed that their ester biosynthesis capacity was limited by the precursor concentrations. Ethyl acetate and ethyl lactate were produced by all strains, except for those of Frul. sanfranciscensis. These results suggested that one of the esterase-encoding genes considered could be implicated in the ethyl acetate and/or ethyl lactate biosynthesis. Overall, the ester biosynthesis capacity by LAB is of great interest in view of fruity flavor formation during sourdough and sourdough bread productions.

IMPORTANCE

The present study gave insights into the production of esters, which impart fruity flavors to fermented foods, by not only sourdough yeasts but also lactic acid bacteria. It showed that some lactic acid bacteria species can synthesize the esters ethyl acetate (sweet notes) and ethyl lactate (creamy notes) under specific conditions. The information gathered during the present study will enable sourdough bakers and companies from the bakery sector to get more information on how to produce sourdoughs that can add fruity notes to the final products after a rational screening and selection of potential starter culture strains.

Quantitative Assessment of Volatile Profile and Sensory Perception of Artisan Bread Made in the City of Valencia

Artisan bread, known for its simple recipes, natural ingredients, and traditional techniques, has seen a surge in demand, especially following the COVID-19 pandemic. Small bakeries emphasize extended fermentation processes and prioritize sensory qualities in their products. However, the impact of ingredients on the quality characteristics of artisan bread remains underexplored. Here, a set of breads from artisanal bakeries in Valencia, Spain, was characterized. Bread dough pH, total titratable acidity (TTA), and acid content were influenced by flour type and sourdough use, creating different environments for volatile compound (VOC) generation. Over 50 VOCs, including aldehydes, alcohols, acids, and furans, were identified in crumb and crust samples of most artisan bread samples, compared to fewer than 20 VOCs in control industrial bread, where ketones dominated. Whole flours, such as spelt, durum wheat, or T80, along with the leavening agent, affected the abundance of certain volatiles, particularly in the crust. Additionally, the use of spelt or wheat flour impacted crumb texture, while sourdough improved taste intensity, acidity, and crumb color. Finally, certain sensory attributes were also influenced by the presence of hydrocarbons and furans in the volatile fraction of both crumb and crust. Overall, the results provide new insights into the influence of ingredients on the quality of artisan bread and can help bakers refine recipes while maintaining a natural ingredient list. Hence, the work is substantial for the artisan bread industry and consumers.

Balancing Maillard reaction products formation and antioxidant activities for improved sensory quality and health benefit properties of pan baked buns

This study investigated the impact of processing temperatures (190 °C, 210 °C, and 230 °C) and durations (7 min, 10 min, and 14 min) on the formation of Maillard reaction products (MRPs) and antioxidant activities in pan baked buns. Key Maillard reaction indicators, including glyoxal (GO), methylglyoxal (MGO), 5-hydroxymethylfurfural (5-HMF), melanoidins, and fluorescent advanced glycation end products (AGEs) were quantified. The results demonstrated significant increases in GO, MGO, 5-HMF contents (p < 0.05), and antioxidant activities (p < 0.05) when the buns were baked at 210 °C for 14 min, 230 °C for 10 min and 14 min. However, the interior MRPs of baked buns were minimally affected by the baking temperature and duration. Prolonged heating temperatures and durations exacerbated MRPs production (43.8 %-1038 %) in the bottom crust. Nonetheless, this process promoted the release of bound phenolic compounds and enhanced the antioxidant activity. Heating induces the thermal degradation of macromolecules in food, such as proteins and polysaccharides, which releases bound phenolic compounds by disrupting their chemical bonds within the food matrix. Appropriate selections of baking parameters can effectively reduce the formation of MRPs while simultaneously improve sensory quality and health benefit of the pan baked buns. Considering the balance between higher antioxidant properties and lower MRPs, the optimal thermal parameters for pan baked buns were 210 °C for 10 min. Furthermore, a normalized analysis revealed a consistent trend for GO, MGO, 5-HMF, fluorescent AGEs, and melanoidins. Moreover, MRPs were positively correlated with total contents of phenolic compounds, ferric-reducing antioxidant power (FRAP), and color, but negatively correlated with moisture contents and reducing sugars. Additionally, the interaction between baking conditions and Maillard reactions probably contributed to enhanced primary flavors in the final product. This study highlights the importance of optimizing baking parameters to achieve desirable MRPs levels, higher antioxidant activity, and optimal sensory attributes in baked buns.

Unraveling chemical changes associated with the sensory quality of Chinese steamed bread as altered by wheat flour type

Chinese steamed bread (CSB) is an important staple of the Chinese people, and its flavor profile is mostly affected by wheat varieties among others. This study selected wheat flour made from three different wheat varieties and investigated their contribution to the CSB flavor profile in terms of metabolism. Thirteen aroma-active compounds identified by GC-O were determined as the main contributors to the different aroma profiles of three CSBs. 350 sensory trait-related metabolites were obtained from five key modules via weighted gene co-expression network analysis. It was found that the sensory characteristics of CSBs made of different wheat flour were significantly different. The higher abundance of lipids in Yongliang No.4 (YL04) wheat flour was converted to large number of fatty acids in fermented dough, which led to the bitterness of CSB. Besides, the abundance in organic acids and fatty acids contributed to the sour, milky, wetness and roughness attributes of YL04-CSB. More fatty amides and flavonoids in Jiangsu Red Durum wheat flour contributed to the fermented and winey attributes of CSB. Carbohydrates with higher abundance in Canadian wheat flour was involved in sugar-amine reaction and glucose conversion, which enhanced the sweetness of CSB. In addition, fatty acids, organic acids, amino acids, and glucose were crucial metabolites which can further formed into various characteristic compounds such as hexanal, hexanol, 2,3-butanediol, acetoin, and 2,3-butanedione and thus contributed to the winey, fresh sweet, and green aroma properties. This study is conductive to better understand the evolution of the compounds that affect the quality and aroma of CSBs.

Unraveling the complex nexus: Interplay of volatile compounds, free amino acids, and metabolites in oat solid state fermentation

This study delves into the dynamic interplay of volatile compounds, free amino acids, and metabolites, meticulously exploring their transformations during oat fermentation. Analysis via gas chromatography-mass spectrometry (GC-MS) unveiled significant alterations: 72 volatile compounds in unfermented oats (NFO) and 60 in fermented oats (FO), reflecting the profound impact of Saccharomyces cerevisiae TU11 and Lactobacillus plantarum Heal19 on oat constituents. A marked increase in Heptane (5.7-fold) and specific alcohol compounds, like 2-methyl-1-propanol, 3-methyl-1-butanol, and Phenylethyl alcohol in FO samples, while reductions in Hexanal, Hexanoic acid, and Acetic acid were observed. Notably, 4 phenolic compounds emerged post-fermentation, revealing diverse microbial actions in flavor modulation. Orthogonal-partial least squares discriminant analysis (OPLS-DA) indicated a clear separation between NFO and FO, demonstrating distinct volatile compound profiles. Further analysis revealed a noteworthy decrease in all free amino acids except for a significant increase in serine during fermentation. Differential metabolite screening identified 354 metabolites with 219 upregulated and 135 down-regulated, uncovering critical markers like isophenoxazine and imidazole lactic acid. Correlation analyses unveiled intricate relationships between volatile compounds and diverse metabolites, illuminating underlying biochemical mechanisms shaping oat flavor profiles during fermentation.

Nutritional composition, in vitro carbohydrates digestibility, textural and sensory characteristics of bread as affected by ancient wheat flour type and sourdough fermentation time

This study aimed to investigate the effect of ancient wheat flour type and sourdough fermentation time on the nutritional, textural and sensorial properties of fiber-rich sourdough bread. The proximate composition, minerals, carbohydrates, organic acids, volatiles, total phenolic content, simulated gastrointestinal digestion, textural and sensorial characteristics were investigated. Bread's minerals, total phenolics, cellulose contents and radical scavenging activity variations clearly indicates an increasing trend with sourdoughs fermentation time. Compared to maltose and glucose, fructose was predominant in all bread samples. Sourdough fermentation time and wheat type had non-significant influence on fructose content from digested fraction. Excepting emmer bread, fermentation time increased in vitro digestibility values for tested samples. The crumb textural parameters (hardness, gumminess, chewiness, cohesiveness and springiness index) were positively influenced by fermentation time. The specific clustering of the analysed characteristics distinguished emmer bread from other samples in terms of volatile compounds, textural and overall acceptability, being preferred by panellists.

Technological and Nutritional Aspects of Bread Production: An Overview of Current Status and Future Challenges

Bakery products, especially bread, exist in many homes worldwide. One of the main reasons for its high consumption is that the main raw material is wheat, a cereal that can adapt to a wide variety of soils and climates. However, the nutritional quality of this raw material decreases during its industrial processing, decreasing the value of fibers, proteins, and minerals. Therefore, bread has become a product of high interest to increase its nutritional value. Due to the high consumption of bread, this paper provides a general description of the physicochemical and rheological changes of the dough, as well as the sensory properties of bread by incorporating alternative flours such as beans, lentils, and soy (among others). The reviewed data show that alternative flours can improve fiber, macro, and micronutrient content. The high fiber content reduces the quality of the texture of the products. However, new processing steps or cooking protocols, namely flour proportions, temperature, cooking, and fermentation time, can allow adjusting production variables and optimization to potentially overcome the decrease in sensory quality and preserve consumer acceptance.

Headspace volatiles profiles of different spring varieties and a wild relative of wheat flour

Volatile profiling was conducted on four wheat varieties Triticum aestivum cv. Chinese Spring (CS), Highbury (High), Paragon (Para), Pavon76 (Pav76), and one wild relative Triticum timopheevii (P95). Headspace solid-phase microextraction (SPME) combined with gas chromatography-mass spectrometry (GC-MS) was used to explore differences in flavor formation mechanisms in different flours before and after starch gelatinization. Solvent retention capacity (SRC) analysis revealed subtle differences in water absorption, gluten strength, and starch characteristics across wheat flour types. Rapid Visco Analysis (RVA) of whole wheat flour demonstrated significant variations in pasting properties among wheat varieties, with P95 exhibiting higher viscosities compared to CS and High potentially influenced by starch gelatinization, protein-starch interactions, and lipid content. Aroma contributions of P95 clustered positively in PCA plots, contrasting with the four main varieties, indicative of species-level differentiation. Furthermore, the study highlighted the roles of viscosity, protein structure, lipid content, and fatty acid composition in modulating the release and perception of volatile aroma compounds during heating. This study sheds light on how the distinct characteristics of wheat flour influence aroma profiles, revealing species-level differences and the pivotal role of physiochemical properties in shaping flavor development mechanisms.

Effects of fatty acid hydroperoxides produced by lipoxygenase in wheat cultivars during dough preparation on volatile compound formation

The formation of volatile compounds affects the flavor of processed wheat flour products. Herein, the effects of the composition of fatty acid hydroperoxides and the differences in the antioxidant contents among wheat cultivars on the flavor of wheat flour products were clarified. For this purpose, the volatile compounds in wheat flour doughs, LOX activity, fatty acid hydroperoxide composition from fractionated LOX, and antioxidant content were analyzed. Norin61 exhibited a high LOX activity and 9-fatty acid hydroperoxide production. Unsaturated aldehydes derived from 9-fatty acid hydroperoxides contributed significantly to the volatile compound profile of Norin61. Moreover, the lowest lutein content was observed in Norin61 among the analyzed cultivars. The LOX activity and composition of the fatty acid hydroperoxides produced by LOX affected the production of volatile compounds, whereas carotenoids had a suppressive effect. This study provides useful information for product design with the desired flavor for developing various processed wheat flour products.

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.

Minimal influence of milling technique in contrast to sourdough on the nutritional and organoleptic quality of bread

A number of studies have shown the effect of cereals and sourdough on bread nutritional and organoleptic quality, but the impact of the milling technique remains little studied. There are two main types of milling technic depending on the bread-making food chain. Industrial bakeries mainly use roller mills while artisanal bakeries may also use stone mill. We set up a participatory experiment with six millers and four bakers to study the impact of these two milling techniques on the quality of flours, sourdough microbiota and the quality of breads. Millers made twenty-two different flours from four different wheat grain varieties using either roller or stone mills. Each baker initiated and maintained sourdoughs with three roller-milled and three stone-milled flours during at least 32 backsloppings and then made bread. The analysis of flours revealed a typical granulometry profile linked to wheat hardness with higher particle sizes for stone-milled flours. Stone-milled flours also had a higher maltose content. However, the milling technic did not drive the composition of the sourdough microbiota. Moreover, the analysis of bread revealed that variation in bread protein fractions and in bread aroma compounds were more related to the specific baker microbial community than to the milling technique. Carbohydrate contents were clearly linked to the main LAB species metabolism. These results revealed that the sourdough microbial community shapes the organoleptic and nutritional quality of bread more than milling techniques.

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.

Comparative study on key odorants of Jiujiang Fenggang Huangjiu and their succession regularities during aging using sensory-directed flavor analysis

Huangjiu was a Chinese national alcohol with a unique flavor. The key odorants in Jiujiang Fenggang Huangjiu (JJFG) and their succession regularities during aging were systematically researched by a sensomics analysis approach. The volatiles of JJFG were isolated by solvent-assisted flavor evaporation, 77 odorants were identified using gas chromatography-olfactometry-mass spectrometry combined with odor-specific magnitude estimation. Three aroma recombinants, prepared using odorants with odor activity values ≥ 1, all showed good similarities with their corresponding samples (92.1%∼97.5%). After omission/addition tests, 7 new key aroma compounds were found in JJFG, including 1-octen-3-one, 1-pentanol, guaiacol, ethyl 2-hydroxy-4-methylpentanoate, 2-phenethyl acetate, ethyl butanoate, and (E,Z)-2,6-nonadienal. Using orthogonal partial least squares-discriminant analysis, 20 compounds with VIP ≥ 1 were found to be important indicators during aging of JJFG. Among them, sotolon, 3-methylsulfanylpropanal, et al. increased with aging. The improved solid-phase extraction can effectively quantify sotolon, with a recovery rate of 80.96%∼91.75%.

New flavors from old wheats: exploring the aroma profiles and sensory attributes of local Mediterranean wheat landraces

Introduction

During the 20th century, the worldwide genetic diversity of wheat was sharply eroded by continual selection for high yields and industry demands for particular standardized qualities. A collection of Israeli and Palestinian landraces (IPLR) was established to represent genetic diversity, accumulated for ten millennia under diverse environments, which was mostly lost in this transition. As our long-term goal is to study this pre- Green Revolution genetic reservoir, herein we focus on its flour and bread quality and sensorial attributes.

Methods

Initially, a database was built for the entire IPLR collection (n=901) holding both Triticum durum (durum wheat) and T. aestivum (bread wheat) which included genetic and phenotypic characterization of agronomic traits, grain and flour quality. Then, a representative subset of the IPLR was selected and compared to modern varieties for dough quality, rheology, aroma and taste using both whole and refined flours and breads. The sensory panel used 40 subjects who evaluated common protocol or sourdough breads made by four artisan bakers.

Results

Results show modern durum cultivar C-9 had superior rheological properties (gluten index, elasticity, dough development time) as compared with landraces, while bread landrace 'Diar Alla' was markedly preferable for baking in relation to the modern cultivar Gadish. Baking tests and subsequent sensory evaluation clearly demonstrated a preference toward refined breads, apart from whole breads prepared using sourdough starters. In bread wheat, loaves baked using landrace flour were scored higher in several quality parameters, whereas in durum lines, the opposite trend was evident. Loaves baked from landraces 'Diar Alla' and to a lesser extent 'Hittia Soada' presented a markedly different aroma from the control loaves prepared from modern flours, both in terms of overall compositions and individual compounds, including classes such as pyranones, pyrazines, furans and pyrroles (maltol). Modern lines, on the other hand, were consistently richer in terpenes and phenylpropanoids. Further analysis demonstrated a significant association between specific aroma classes and sensory attributes scored by panelists.

Discussion

The findings of the study may help advance new niches in the local wheat market aimed at health and nutrition including adapting durum varieties to the bread market and developing flavor-enhanced wholemeal breads.

Exploring the Effect of Different Storage Conditions on the Aroma Profile of Bread by Using Arrow-SPME GC-MS and Chemometrics

In the present feasibility study, SPME Arrow-GC-MS method coupled with chemometric techniques, was used for investigating the impact of two different storage conditions, namely freezing and refrigeration, on volatile organic compounds (VOCs) of different commercial breads. The SPME Arrow technology was used as it is a novel extraction technique, able to address issues arising with traditional SPME fibers. Furthermore, the raw chromatographic signals were analysed by means of a PARAFAC2-based deconvolution and identification system (PARADISe approach). The use of PARADISe approach allowed for an efficient and rapid putative identification of 38 volatile organic compounds, including alcohols, esters, carboxylic acids, ketones, and aldehydes. Additionally, Principal Component Analysis, applied on the areas of the resolved compounds, was used to investigate the effects of storage conditions on the aroma profile of bread. The results revealed that the VOC profile of fresh bread is more similar to the one of bread stored in the fridge. Furthermore, there was a clear loss of aroma intensity in frozen samples, which could be explained by phenomena related to different starch retrogradation that occurs during freezing and refrigeration. However, considering the limited number of investigated samples, this study must be considered as a proof of concept; a more statistically representative sampling and further examinations of other properties, such as bread texture, need to be performed to better understand whether samples destined for eventual analysis should be frozen or refrigerated.

The potential of almonds, hazelnuts, and walnuts SFE-CO2 extracts as sources of bread flavouring ingredients

Nuts have been part of the human diet since our early ancestors, and their use goes beyond nutritional purposes, for example, as aromatic sources for dairy products. This work explores the potential of almond (Prunus dulcis (Mill.) DA Webb), hazelnut (Corylus avellana L.), and walnut (Juglans regia L.) extracts as sources of food flavouring agents, suggesting a new added-value application for lower quality or excess production fruits. The extracts were obtained by supercritical fluid extraction with carbon dioxide and characterized by: quantification of the volatile fraction by HS-SPME GC-MS; sensory perception and description; and cytotoxicity against Vero cells. All extracts revealed potential as flavouring ingredients due to terpene abundance. No significant differences were observed for the minimal sensory perception, in which the odour threshold values ranged from 8.3 × 10^-4 to 6.9 × 10^-3 μg·mL^-1 for walnuts and almonds extracts, respectively. In contrast, the cytotoxic potential differed significantly among the extracts, and P. dulcis extract presented lower cytotoxicity. Notes as woody, fresh, and green were identified in the volatile intensifiers obtained from the P. dulcis extract. Thus, almond extract was identified as the most promising ingredient to increase the sensory value of food products, namely bread. This potential was verified by an increase in the odour perception of bread after adding 4 μL of extract to each 100 g of bread dough. The quantified eucalyptol and d-limonene terpenes - found in the P. dulcis extract - have improved the release of the pleasant and natural volatile compounds from bread crust and crumb compared to the control bread chemical and sensory profiles.

Study of the Fermentation Characteristics of Non-Conventional Yeast Strains in Sweet Dough

Despite the diverse functions of yeast, only a relatively homogenous group of Saccharomyces cerevisiae yeasts is used in the baking industry. Much of the potential of the natural diversity of yeasts has not been explored, and the sensory complexity of fermented baked foods is limited. While research on non-conventional yeast strains in bread making is increasing, it is minimal for sweet fermented bakery products. In this study, the fermentation characteristics of 23 yeasts from the bakery, beer, wine, and spirits industries were investigated in sweet dough (14% added sucrose w/w dm flour). Significant differences in invertase activity, sugar consumption (0.78-5.25% w/w dm flour), and metabolite (0.33-3.01% CO₂; 0.20-1.26% ethanol; 0.17-0.80% glycerol; 0.09-0.29% organic acids) and volatile compound production were observed. A strong positive correlation (R² = 0.76, p < 0.001) between sugar consumption and metabolite production was measured. Several non-conventional yeast strains produced more positive aroma compounds and fewer off-flavors than the reference baker's yeast. This study shows the potential of non-conventional yeast strains in sweet dough.

Effect of Alkali on the Microbial Community and Aroma Profile of Chinese Steamed Bread Prepared with Chinese Traditional Starter

Alkali is an indispensable additive in Chinese steamed bread (CSB) production. This work aimed to evaluate the key roles of alkali in the microbial community of dough fermented using Chinese traditional starter (CTS) and the aroma profiles of CSB. The dominant fungi in CTS and fermented dough were members of the phylum Ascomycota and the genus Saccharomyces. Pediococcus, Companilactobacillus, and Weissella were the dominant bacterial genera in CTS and fermented dough. Adding alkali could retain the types of dominant yeasts and LAB derived from CTS, decrease the relative abundance of Companilactobacillus crustorum and Weissella cibaria, and increase that of Pediococcus pentosaceus, in fermented dough. Principal component analysis (PCA) indicated that adding alkali decreased the content of sourness-related volatiles in CSB fermented by CTS. Correlation analysis showed that Pediococcus and Weissella in fermented dough were positively correlated with the lipid oxidation flavor-related compounds in CSB, and Lactobacillus was positively correlated with sourness-related aroma compounds. Synthetic microbial community experiments indicated that CSB fermented by the starter containing P. pentosaceus possessed a strong aroma, and adding alkali weakened the flavor intensity. Alkali addition could promote the formation of ethyl acetate and methyl acetate with a pleasant fruity aroma in W. cibaria-associated CSB.

Technology characteristics and flavor changes of traditional green wheat product nian zhuan in Northern China

Nian zhuan has its aroma as one of the perceived principal characteristics. The current study was aimed mainly to investigate the potential to include the aroma of nian zhuan as a new target criterion into the green wheat product chain. By improving the conditions for the traditional processing of nian zhuan, the optimal processing conditions were determined as green wheat (GW) 14 d, steaming the green wheat with the skin (SGWS) 26 min and cooked green wheat peeled (CGWP) 280 min, to evaluate the feasibility of using electronic nose (E-nose) and gas chromatography mass spectrometry (GC-MS) to discriminate nian zhuan in different stages. E-nose was used to recognize nian zhuan odors in different processing stages, and GC-MS to identify the individual volatile compounds. A total of 139 volatile compounds were detected by GC-MS, of which 71 key were screened by t-test (P &lt; 0.01). The W1W, W1S, W2W and W2S sensors of E-nose gave higher responses to all samples, and effectively discriminated the samples. The most volatile compounds were produced in the millstone milling (MSM) stage of nian zhuan, and millstone could promote the release of volatile compounds from cooked green wheat by milling.

Tracking Wheat Variety and Origin by the Shape Analysis of the Volatiles Fingerprint of Wheat Kernels and Wheat Beers

The Volatile Organic Compounds (VOCs) of common wheat of different origin (variety and altitude of cultivation) and craft wheat beers produced by using the wheat themselves were analyzed by SPME GC-MS. The VOCs of wheat kernels and wheat beers were compared, and 14 common flavor-active compounds were identified. Principal component analysis was used to describe changes in the profile of common volatiles induced by beer processing. A unifying approach by Generalized Procrustes analysis (GPA), which considers the overall characteristics of the datasets, permitted linking the VOCs of wheat to those of beers and to define a common flavor pattern. Despite the beer processing deeply affecting the overall volatilome profile, a consensus map permitted to clearly classify the VOCs profile of five out of six samples. This work revealed that differences in wheat VOCs induced by wheat variety and cultivation site were reflected in different beer aromatic profiles, highlighting the importance of origin on the wheat and beers’ flavor. This unifying approach to flavor analysis by GPA could be of help in sight of a certification of origin, since it may contribute not only to the definition of wheat origin but also of the “terroir” of wheat beer thereof.

The study of microbial diversity and volatile compounds in Tartary buckwheat sourdoughs

Microorganisms play an essential role in forming volatile compounds in traditional staple products. Tartary buckwheat, as a medicinal and food material, has high nutritional value but its development and utilization are seriously restricted due to its poor flavor. In this study, 16S rRNA and ITS rRNA sequencing were used to analyze the microbial diversity of Tartary buckwheat sourdoughs, while HS-SPME-GC/MS was used to identify volatile compounds during fermentation. The results showed that Lactococcus and Weissella were the dominant bacterial genus. Wickerhamomyces, Penicillium, and Aspergillus were the main fungal genera in the Tartary buckwheat sourdoughs. And the main volatile compounds in Tartary buckwheat sourdough were pyrazine compounds. After 12 h of fermentation, a large amount of alcohol and esters were produced, which endowed the sourdough with a good flavor. This suggests that sourdough fermentation could significantly improve the flavor of Tartary buckwheat.

Production of volatiles relation to bread aroma in flour-based fermentation with yeast

The aim of this study is to produce a bread aroma mixture in flour-based fermentation that can potentially be added in bread dough forming after selection of yeast strains and optimization of the fermentation conditions. S. cerevisiae PFC121 produced bread aroma compounds in higher amounts compared to other 20 strains. Also, this strain provided a more balanced volatiles in bread samples that gained consumer appreciation. When the PLS analysis were evaluated, 3-methyl-1-butanol, 2-phenylethyl alcohol, nonanal, and benzaldehyde were closely related with the whole wheat flour. Conversely, 2-methyl-1-propyl acetate, and 2-methyl-1-propanol were observed to be correlated with the fermentation temperature. PCA showed that 20 °C fermentation temperature was effective on the accumulation of benzaldehyde and nonanal. Extending the fermentation time increased alcohol and ester accumulation. In conclusion, S. cerevisiae PFC121 is a potential strain to produce bread related volatiles at the fermentation conditions that are wheat flour, 30 °C, 6 pH and 48-h.

Comprehensive Two-Dimensional Gas Chromatography as a Powerful Strategy for the Exploration of Broas Volatile Composition

Broa is a Portuguese maize bread with characteristic sensory attributes that can only be achieved using traditional maize varieties. This study intends to disclose the volatile compounds that are mainly associated with the baking process of broas, which can be important contributors to their aroma. Twelve broas were prepared from twelve maize flours (eleven traditional maize varieties and one commercial hybrid). Their volatile compounds were analyzed by GC×GC–ToFMS (two-dimensional gas chromatography coupled with time-of-flight mass spectrometry) for an untargeted screening of the chemical compounds mainly formed during baking. It was possible to identify 128 volatiles that belonged to the main chemical families formed during this stage. Among these, only 16 had been previously detected in broas. The most abundant were furans, furanones, and pyranones, but the most relevant for the aroma of broas were ascribed to sulfur-containing compounds, in particular dimethyl trisulfide and methanethiol. Pyrazines might contribute negatively to the aroma of broas since they were present in higher amounts in the commercial broa. This work constitutes the most detailed study of the characterization of broas volatile compounds, particularly those formed during the Maillard reaction. These findings may contribute to the characterization of other maize-based foodstuffs, ultimately improving the production of foods with better sensory features.

Variation of Volatile Compounds and Corresponding Aroma Profiles in Chinese Steamed Bread by Various Yeast Species Fermented at Different Times

To control the fermentation process of yeast-Chinese steamed bread (CSB), the volatile compounds and odor profiles of yeast-CSBs during fermentation were comprehensively investigated by sensory evaluation, gas chromatography-mass spectrometry, gas chromatography-olfactometry (GC-O), and odor activity value (OAV). Eight sensory attributes were established, and quantitative descriptive analysis results showed that CF1303-CSB had intense sweet and sweet aftertaste attributes, CF1318-CSB was characterized by milky, wheaty, and yeasty attributes, while CL10138-CSB presented distinct sour, winy, and floury attributes. A total of 41 key aroma-active compounds were detected, and phenylethyl alcohol was the most potent aroma compound with a flavor dilution (FD) of 1024. CF1303-CSB, CF1318-CSB, and CL10138-CSB contained 24, 22, and 21 key aroma compounds, respectively, based on the OAV. These key aroma compounds can be used as the potential markers to monitor the yeast-CSBs during the fermentation process. Five compounds, including β-myrcene, 2-phenoxyethanol, methyl cinnamate, guaiacol, and o-cresol, were first identified in CSB. These results provide theoretical basis for processing and quality control of yeast-CSBs.

Could environmental effect overcome genetic? A chemometric study on wheat volatiles fingerprint

A deeper knowledge of the causes of volatile organic compounds (VOCs) variance in wheat is crucial for quality improvement and control of its derivatives. The VOCs profile of common and durum wheat kernels grown in different fields sited at different altitudes over two years was analysed and 149 compounds were identified by gas chromatography-mass spectrometry. Principal component analysis evidenced that the year of cultivation was the highest source of VOCs variance. The effects of wheat origin, as described by the cultivation site, its elevation, and species were further investigated by PLS-DA, that permitted to correctly classify wheat of different origin on the basis of its VOCs profile. The importance of the different effects was investigated by multidimensional test and resulted: year of cultivation > field of cultivation > species > altitude. Findings suggest that environmental conditions are more important than species in the determination of the VOCs variance of wheat.

Volatiles profile of 'Blanche' wheat craft beer as affected by wheat origin: A chemometric study

The aroma of craft beers is recognized to affect their overall acceptability and drinkability. Raw materials can affect the volatile organic compounds (VOCs) of beers and their aroma. The VOCs profile of wheat craft beers produced with wheat (Triticum aestivum, L.) of different origin (variety and cultivation site) in increasing concentration was analysed. PLS2 analysis evidenced that wheat concentration is the main factor affecting VOCs profile, whilst the effect of variety (Vittorio and Solina) and altitude of cultivation (70, 500 and 1,200 m a.s.l.) on VOCs variance was lower. PLS-DA permitted to differentiate beers obtained with the two varieties for their VOCs profile: 2-Ethylhexanol, a cultivar specific indicator, was found in beers made with Solina.

Lactic acid bacteria synergistic fermentation affects the flavor and texture of bread

Fermentation strains play a key role in the quality of bread. The combination of yeast and lactic acid bacteria (LAB) may effectively improve the function and nutritional properties of bread. In this study, the dough was fermented to make bread by using single strain (Saccharomyces cerevisiae, mode A), the combination of two strains (S. cerevisiae and Lactiplantibacillus plantarum, mode B; S. cerevisiae and Lactobacillus delbrueckii, mode C), or three strains (S. cerevisiae, L. plantarum, and L. delbrueckii, mode D). The specific volume, texture, and aroma substances of bread were evaluated. The possibility of mixed fermentation of selected yeast and LAB to replace natural fermentation dough was evaluated. The results showed that the specific volume of bread in mode B was 15.2% higher than that of mode A. The structure was softer and the taste was more vigorous in mode B bread. The content of volatile compounds was highest in mode B bread among the four mode bread. The characteristic flavors were ethyl 2-hydroxypropionate and z-3-hexenol. The cofermentation in mode B made the bread aroma richer and gave better aroma characteristics to bread. Therefore, the fermentation of S. cerevisiae and L. plantarum can be recommended to replace naturally fermented dough to improve the quality of bread. PRACTICAL APPLICATION: L. plantarum and L. delbrueckii, separately or together, assisted in yeast fermentation to make bread. The specific volume, texture, and aroma substances of bread were evaluated to replace natural fermented dough with mixed fermentation. L. plantarum-assisted yeast fermentation improved the specific volume, texture, and aroma of bread. The characteristic flavors were ethyl 2-hydroxypropionate and z-3-hexenol in bread. Therefore, the fermentation of S. cerevisiae and L. plantarum could replace naturally fermented dough to improve the quality of bread.

Evolution of volatiles and quality of Chinese steamed bread during storage at different temperatures

The aim of this work is to investigate the evolution of volatiles and quality of CSB during 4 d of storage at 4 °C and 25 °C, respectively. Rapidly increasing hardness and decreasing resilience were observed in CSB after 1 d of storage at 4 °C. However, relative soft CSB was found after 1 d of storage at 25 °C as a result of the lower rate of retrogradation. Volatiles were monitored by gas chromatography-mass spectrometer. Significant (P < 0.05) decrease of 4 esters and 2-pentylfuran were observed with prolonged storage time for CSB stored at both 4 °C and 25 °C. PCA analysis indicated that the storage temperature of 4 °C was beneficial to remain CSB volatiles during long storage time (2-4 d). These findings might be beneficial to retain more volatiles and quality and finally extend shelf-life of CSB.

Wheat Proteins: A Valuable Resources to Improve Nutritional Value of Bread

Triticum aestivum, commonly known as bread wheat, is one of the most cultivated crops globally. Due to its increasing demand, wheat is the source of many nutritious products including bread, pasta, and noodles containing different types of seed storage proteins. Wheat seed storage proteins largely control the type and quality of any wheat product. Among various unique wheat products, bread is the most consumed product around the world due to its fast availability as compared to other traditional food commodities. The production of highly nutritious and superior quality bread is always a matter of concern because of its increasing industrial demand. Therefore, new and more advanced technologies are currently being applied to improve and enrich the bread, having increased fortified nutrients, gluten-free, highly stable with enhanced shelf-life, and long-lasting. This review focused on bread proteins with improving wheat qualities and nutritional properties using modern technologies. We also describe the recent innovations in processing technologies to improve various quality traits of wheat bread. We also highlight some modern forms of bread that are utilized in different industries for various purposes and future directions.

Impact of Malt Extract Addition on Odorants in Wheat Bread Crust and Crumb

Application of gas chromatography-olfactometry and aroma extract dilution analysis to the volatiles isolated from (1) crust and (2) crumb of a wheat bread made with the addition of a dark liquid malt extract (LME) to the dough and (3) crust and (4) crumb of a reference bread made without addition resulted in the identification of 23 major odorants. Their quantitation followed by the calculation of odor activity values (OAV = ratio of concentration to odor threshold value) suggested that LME addition influenced the aroma of the bread predominantly by increasing seasoning-like smelling sotolon in crust and crumb, and caramel-like smelling compounds maltol and 4-hydroxy-2,5-dimethylfuran-3(2H)-one (HDMF) in the crumb. The increase in sotolon and maltol was explainable by direct transfer from the LME to the bread, whereas HDMF must have been formed from LME-derived precursors. This difference needs to be considered in the targeted optimization of LMEs for bread making.

Ancient Wheat Species: Biochemical Profile and Impact on Sourdough Bread Characteristics—A Review

In recent years, the attention of farmers, bakers and consumers towards ancient wheat species has been increasing. Low demands of pedo-climatic growth factors, the suitability for organic cultivation along with their high nutritional quality and their content in pro-health compounds make them extremely attractive for bakers and modern consumers, equally. On the other hand, in recent years, sourdough has gained attention due to its ability to produce new functionally active molecules with higher bioaccessibility and thus to produce bread with enhanced nutritional quality. This paper highlights the relevant nutritional profile of einkorn, spelt, emmer and Khorasan which could lead to bread with improved textural, sensorial, microbial and nutritional characteristics through sourdough fermentation. The ancient wheat species could be used as promising substitutes for common wheat flour for the design of innovative types of bread, even for special needs.

Shedding Light on the Volatile Composition of Broa, a Traditional Portuguese Maize Bread

In Portugal, maize has been used for centuries to produce an ethnic bread called broa, employing traditional maize varieties, which are preferred by the consumers in detriment of commercial hybrids. In order to evaluate the maize volatiles that can influence consumers’ acceptance of broas, twelve broas were prepared from twelve maize varieties (eleven traditional and one commercial hybrid), following a traditional recipe. All maize flours and broas were analyzed by HS-SPME-GC-MS (headspace solid-phase microextraction) and broas were appraised by a consumer sensory panel. In addition, the major soluble phenolics and total carotenoids contents were quantitated in order to evaluate their influence as precursors or inhibitors of volatile compounds. Results showed that the major volatiles detected in maize flours and broas were aldehydes and alcohols, derived from lipid oxidation, and some ketones derived from carotenoids’ oxidation. Both lipid and carotenoids’ oxidation reactions appeared to be inhibited by soluble phenolics. In contrast, phenolic compounds appeared to increase browning reactions during bread making and, consequently, the production of pyranones. Traditional samples, especially those with higher contents in pyranones and lower contents in aldehydes, were preferred by the consumer sensory panel. These findings suggest that, without awareness, consumers prefer broas prepared from traditional maize flours with higher contents in health-promoting phenolic compounds, reinforcing the importance of preserving these valuable genetic resources.

Sourdough production: fermentation strategies, microbial ecology, and use of non-flour ingredients

Sourdough production is an ancient method to ferment flour from cereals for the manufacturing of baked goods. This review deals with the state-of-the-art of current fermentation strategies for sourdough production and the microbial ecology of mature sourdoughs, with a particular focus on the use of non-flour ingredients. Flour fermentation processes for sourdough production are typically carried out by heterogeneous communities of lactic acid bacteria and yeasts. Acetic acid bacteria may also occur, although their presence and role in sourdough production can be criticized. Based on the inoculum used, sourdough productions can be distinguished in fermentation processes using backslopping procedures, originating from a spontaneously fermented flour-water mixture (Type 1), starter culture-initiated fermentation processes (Type 2), and starter culture-initiated fermentation processes that are followed by backslopping (Type 3). In traditional recipes for the initiation and/or propagation of Type 1 sourdough productions, non-flour ingredients are often added to the flour-water mixture. These ingredients may be the source of an additional microbial inoculum and/or serve as (co-)substrates for fermentation. An example of the former is the addition of yoghurt; an example of the latter is the use of fruit juices. The survival of microorganisms transferred from the ingredients to the fermenting flour-water mixture depends on the competitiveness toward particular strains of the microbial species present under the harsh conditions of the sourdough ecosystem. Their survival and growth is also determined by the presence of the appropriate substrates, whether or not carried over by the ingredients added.

Functional, Nutritional, and Sensory Quality of Mixed Flours-Based Breads as Compared to Durum Wheat Semolina-Based Breads

Increasing preference of consumers and bakers towards bread manufactured with mixed flours and/or sourdough drove us to investigate about influence of flours and sourdough on crumb grain, chemical, sensory, and in vitro glycaemic index (GI) and antioxidant activity of bread. To this aim, we produced and compared six experimental breads: three were based on a mixture of flours (soft wheat, durum wheat semolina, barley, oat, rye, and buckwheat); three were semolina-based breads. Two different sourdoughs (wheat or mixed flours) were assessed. Compared to semolina breads, those containing a mixture of flours showed higher specific volume. The use of sourdough led to increased concentrations of total free amino acids (FAA). Mixed flours bread with addition of mixed flours sourdough was rich in some essential FAA and amino acid derivative bioactive gamma-aminobutyric acid. Type of flours had higher influence than sourdough addition on volatile organic compounds. All the mixed flours breads, although showing profiles of volatile organic compounds differing from those of semolina breads, resulted acceptable. In addition, they had lower GI and higher antioxidant activity than semolina breads. Type of flours had much higher impact on GI and antioxidant activity than sourdough.

Non-Conventional Yeasts as Alternatives in Modern Baking for Improved Performance and Aroma Enhancement

Saccharomyces cerevisiae remains the baker’s yeast of choice in the baking industry. However, its ability to ferment cereal flour sugars and accumulate CO2 as a principal role of yeast in baking is not as unique as previously thought decades ago. The widely conserved fermentative lifestyle among the Saccharomycotina has increased our interest in the search for non-conventional yeast strains to either augment conventional baker’s yeast or develop robust strains to cater for the now diverse consumer-driven markets. A decade of research on alternative baker’s yeasts has shown that non-conventional yeasts are increasingly becoming important due to their wide carbon fermentation ranges, their novel aromatic flavour generation, and their robust stress tolerance. This review presents the credentials of non-conventional yeasts as attractive yeasts for modern baking. The evolution of the fermentative trait and tolerance to baking-associated stresses as two important attributes of baker’s yeast are discussed besides their contribution to aroma enhancement. The review further discusses the approaches to obtain new strains suitable for baking applications.