Wheat bread aroma compounds in crumb and crust: A review

Quantitative Determination of Thiamine-Derived Taste Enhancers in Aqueous Model Systems, Natural Deep Eutectic Solvents, and Thermally Processed Foods

To obtain high-kokumi-active building blocks, which can be used to produce savory process flavors, it is essential to obtain a better understanding on the formation rate of kokumi-active compounds, such as 3-(((4-amino-2-methylpyrimidin-5-yl)methyl)thio)-5-hydroxypentan-2-one or 2-methyl-5-(((2-methylfuran-3-yl)thio)methyl)pyrimidin-4-amine. The present work showed quantitative studies in several model reaction systems on the recently discovered kokumi-active thiamine derivates. It was possible to show that the thiamine conversion in aqueous model reactions could be directed toward the taste-modulating compounds by adjusting the pH value (6.5), the heating time (120 min), and the heating temperature (120 °C). With the development of a new natural deep eutectic solvents (NADES) system consisting of thiamine, cysteine, ribose, and sodium hydroxide, it was possible to obtain high yields of the targeted taste-modulating analytes, such as 3-(((4-amino-2-methylpyrimidin-5-yl)methyl)thio)-5-hydroxypentan-2-one and 2-methyl-5-(((2-methylfuran-3-yl)thio)methyl)pyrimidin-4-amine. Furthermore, the current study showed that kokumi-active thiamine derivates, such as S-((4-amino-2-methylpyrimidin-5-yl)methyl)-l-cysteine, 3-(((4-amino-2-methylpyrimidin-5-yl)methyl)thio)-5-hydroxypentan-2-one, 2-methyl-5-(((2-methylfuran-3-yl)thio)methyl)pyrimidin-4-amine, and 5-(((furan-2-ylmethyl)thio)methyl)-2-methylpyrimidin-4-amine, can be classified as natural "food-borne" taste enhancers and occur in thiamine-rich, thermally treated foodstuff.

Characterization of the key odorants contributing to retronasal olfaction during bread consumption

Gas chromatography-ion mobility spectrometry (GC-IMS) and dynamic quantitative descriptive analysis (D-QDA) were combined to explore the aroma release and perception from the retronasal cavity during bread consumption. D-QDA results elucidated that the sweet, creamy, and roasty notes were the most active attributes during oral processing. The final stage of oral processing had the most complicated changing pattern, followed by the intermediate and initial stages. Thirteen aroma compounds were detected in the retronasal cavity, of which eight had odor activity values (OAVs) greater than 1. The total OAV changing pattern was consistent with the D-QDA results. Addition experiments further confirmed that acetoin, 2,3-butanedione, and 3-(methylthio)propanal were key aroma compounds contributing to retronasal olfaction. 2,3-Butanedione and 3-(methylthio)propanal were both identified as key odorants in the mouth cavity and retronasal cavity during oral processing, but they had 30% loss during the breath delivery from the mouth cavity to the retronasal cavity.

Deterioration mechanisms of high-moisture wheat-based food - A review from physicochemical, structural, and molecular perspectives

Wheat-based products are staple foods for over a third of the world's population. However, most wheat-based staple foods are provided with a high water content to maintain naturally chewable mouthfeel, which leads to a short shelf life and limits their distribution and marketing. Understanding the fundamental mechanisms and dynamics that drive the quality deterioration is therefore essential for obtaining alternative technologies for optimal quality and extended shelf life. Here, we provide the basis for the physicochemical, structural, and molecular changes occurring in various wheat products during storage, intending to elucidate the underlying deterioration causes. Generally, more desirable qualities are obtained for fresh wheat products, both in appearance and mouthfeel. During storage, changes in the physicochemical properties, structure, main constituents, and water status contribute to the quality deterioration. Based on these changes, deterioration mechanisms are summarized to provide both theoretical and practical references for the quality regulation of high-moisture wheat-based food.

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.

Aroma and quality of breads baked from old and modern wheat varieties and their prediction from genomic and flour-based metabolite profiles

Bread aroma is the principal characteristic perceived by the consumer yet it is mostly disregarded in the product chain. The main aim of this study was to evaluate the potential to include bread aroma as a new target criterion into the wheat product chain. The objectives of our study were to (i) quantify the influence of genetic versus environmental factors on the bread aroma and quality characteristics, (ii) evaluate whether bread baked from modern wheat varieties differ in terms of aroma from those baked from old varieties, and (iii) compare genomic and metabolomic approaches for their efficiency to predict bread aroma and quality characteristics in a wheat breeding program. Agronomic characters as well as bread aroma and quality traits were assessed for 18 old and 22 modern winter wheat varieties evaluated at up to three locations in Germany. Metabolite profiles of all 120 flour samples were collected using a 7200 GC-QTOF. Considerable differences in the adjusted entry means for all examined bread aroma and quality characters were observed. For aroma, which was rated on a scale from 1 to 9, the adjusted entry means varied for the 40 wheat varieties between 3 and 8. In contrast, the aroma of bread prepared from old and modern wheat varieties did not differ significantly (P < 0.05). Bread aroma was not significantly (P < 0.05) correlated with grain yield, which suggested that it is possible to select for the former character in wheat breeding programs without reducing the gain of selection for the latter. Finally, we have shown that bread aroma can be better predicted using a combination of metabolite and SNP genotyping profiles instead of the SNP genotyping profile only. In conclusion, we have illustrated possibilities to increase the quality of wheat for consumers in the product chain.

Assessment of Enzymatic Improvers in Flours Using LC-MS/MS Detection of Marker Tryptic Peptides

Enzymatic improvers are enzymes obtained from microbial or fungal cultures, added as technical adjuvants to flour, with the aim of improving the dough characteristics in bakery products. They are used in a low ppm range and, being technical adjuvants, can go undeclared on the label. Many types of enzymatic improvers are present on the market, such as amylases, lipases, proteases, xylanases, glucose oxidases, and others, each with a different function. Analytical methods capable of detecting these enzymes are needed, particularly for bakery companies, in order to monitor the quality of raw materials and to detect any undeclared presence. In the present work, specific peptide markers, obtained by enzymatic digestion, have been used to detect the presence of enzymatic improvers by LC-MS/MS techniques. Promising results were obtained for some enzymes acting on the carbohydrate fraction (glucoamylase, glucose oxidase, xylanase) in which amounts as low as 20 ppm could be identified in blind flour samples. For lipases and proteases the method proved to be very effective in terms of specific identification, even if less sensitive.

Fatty Acids, Volatile and Sensory Profile of Multigrain Biscuits Enriched with Spent Malt Rootles

Spent malt rootlets, a by-product of the brewing industry, are a rich source of protein, essential amino acids, healthy fats, polyphenols and minerals, and could be a new promising type of raw material from the nutritional, economic, sensory, and technical perspectives. However, their specific aroma profile could limit their addition in baked products. The aim of this work was to study the effect of spent malt rootlets addition on volatile derivatives of enriched biscuits in relation to their sensory profile. For this purpose, spent malt rootlets and enriched biscuits (0-25% spent malt rootlets added) were analyzed by GC-MS techniques, in order to obtain their fatty acids methyl esters and volatile compounds profile, while for the sensory analysis a nine-point hedonic score test was used. The results of this study reveal the fatty acids and volatile profile of spent malt rootlets and of the enriched biscuits with spent malt rootlets pointing out the contribution of fatty acids to the generation of aroma compounds. The influence of different aroma compounds on the consumer's preferences was studied and the optimum level addition of spent malt rootlets in multigrain biscuits was found to be 15%.

Use of Autochthonous Lactobacilli to Increase the Safety of Zgougou

Seeds of Pinus halepensis are used for preparing zgougou, a spontaneously fermented matrix giving juice and seeds debris, consumed in many Arabian countries, including Tunisia. In the same way as all the food processes based on spontaneous fermentation, zgougou hides health risks due to eventual pathogenic microorganisms and derived toxins. This study aimed at investigating the effect of the use of autochthonous Lactobacillus paraplantarum A1 and Lactobacillus plantarum A2, as fermentation starters, on the microbiological characteristics, profiles of volatile organic compounds (VOC), antibacterial and antioxidant activities of juice and seeds debris from zgougou. The starter lactobacilli inhibited undesired bacteria (e.g., Enterobacter and Aeromonas) and coccus-shaped lactic acid bacteria, as shown by culture-dependent and-independent methods. The inhibitory effect was more evident in juice than in seeds debris. Some VOC (ethanol, acetoin, phenol,2-methoxy and caryophyllene) were present at higher concentrations in juice and seeds obtained upon spontaneous fermentation, compared to the samples deriving from fermentation with lactobacilli. The latter samples were characterized by higher concentrations of acetic acid, decane, 1-nonanol, bornyl acetate and bornyl formate. In addition, they showed a wider spectrum of antibacterial activity than spontaneously fermented juice and seeds. The use of autochthonous lactobacilli did not relevantly affect the antioxidant activity of zgougou. When juice from lactobacilli-driven fermentation was used to prepare a traditional Tunisian pudding ("Assidat-Zgougou"), it improved color and odor with respect to the pudding containing juice from spontaneous fermentation. This study showed that the use, at laboratory scale, of autochthonous lactobacilli is a feasible biotechnological tool to outgrow undesired bacteria, thus improving the safety of zgougou juice. Future studies should be undertaken to confirm the observed benefits at industrial scale.

Impact of sodium reduction strategies on volatile compounds, sensory properties and consumer perception in commercial wheat bread

The efficacy of two sodium reduction strategies in preserving sensory profile and consumer liking of yeasted wheat bread was tested, by combining sensory data, aroma compounds and consumer investigations. The use of (i) a reduced-sodium salt substitute, Pansalt® (NaCl 57%, other salts and minor ingredients) at 1.5%, and (ii) the heterogeneous NaCl distribution (average level of 1%) leading to enhanced saltiness by taste contrast, were compared with standard (1.5%) and reduced (1.0%) addition of NaCl. The heterogeneous NaCl distribution was effective in preserving saltiness. Salt substitution with Pansalt® was less effective but preserved the overall flavour. Higher amount of Maillard reaction volatile products, associated with more intense toasted odour of the crust, was found in breads with higher NaCl content. The consumer survey highlighted satisfactory results of Pansalt® use for 58% of the respondents (equal or higher liking and purchase intention). Heterogeneous salt distribution was effective for 31% of consumers.

Comparison of different bread types: Chemical and physical parameters

In this work, the chemical and physical profile of 5 different bread types (Multicereal bread, Bavaria wheat bread, Wholemeal bread, Rye and Oat bread) were analysed in depth, namely the nutritional profile, individual fatty acids and soluble sugars through GC-FID and HPLC-RI, respectively, as well as the mineral profile, including micro and macroelements. Furthermore, a texture profile analysis was carried out in addition to the measurement of the crust colour. Each bread type showed a distinct profile, with Wholemeal and Bavaria having the lowest calories, and Oat the highest. Multicereal showed the highest amount of unsaturated fatty acids, while Wholemeal and Rye scored the least sodium amounts. The hardest bread was Rye and the easiest to chew were Oat and Bavaria breads. The latter was also the one with the darkest crumb of all the analysed breads. This work shows that bread can be baked to meet the needs and particularities of various kinds of diets.

Analysis of Volatile Compounds from Wheat Flour in the Heating Process

Volatile profiling was carried out during heating through vacuum-assisted headspace solid-phase microextraction combined with gas chromatography-mass spectrometry to better understand the flavor forming mechanism of flour products. Ninety-two volatile compounds were detected and identified, including aldehydes (25), ketones (15), alcohols (9), nitrogen- and sulfur-containing compounds (6), benzene derivatives (15), furans (10), and acids and esters (12). The formation temperature of each volatile was also determined. Results showed that temperature played an important role in the formation and content of volatile compounds. In the low-temperature range (60 °C–100 °C), the flavor composition of flour was mainly composed of C6–C10 volatile aldehydes and alcohols. At temperatures exceeding 100 °C, especially at 120 °C, many long carbon chain aldehydes and alcohols, furans, acids, esters, nitrogen- and sulfur-containing compounds were formed. The formation rate of most identified volatile compounds increased during heating, especially from 90 °C to 130 °C.

Effects of various brans on quality and volatile compounds of bread

The present study aimed to evaluate the effect of various bran sources, including wheat, barley, and rice, on the quality and volatile compounds of Egyptian ‘balady’ bread (Fino). The protein, fat, and total carbohydrates content of the studied brans ranged from 8.49 to 14.16%, 2.16 to 8.12%, and 34.38 to 85.06%, respectively. The mi- neral composition and colour parameters of the brans were also evaluated. The substitution of wheat flour with 10%, 20%, and 30% of different brans resulted in decreased loaf volume and specific volume, and increased loaf weight. A significant decrease in colour parameters (L, a, and b) of the bread crust and crumb were observed in all the sam- ples. The addition of bran at three concentrations showed a remarkable increase in the total phenolic content of the bread samples, compared to the control. The antioxidant activity of the bread samples fortified with brans showed the following order: RB (rice bran) > BB (barley bran) > WB (wheat bran), as determined by the DPPH and β-carotene assays. Thirty-six volatile compounds identified in the bread samples using GC-MS included 5 alcohols, 6 pyrazines, 2 acids, 9 aldehydes, 5 ketones, 3 esters, and 6 sulphur-containing compounds. Alcohols were the predominant vola- tile constituents accounting for 58.3; 61.57; 59.08; and 56.15% in the control and in the bread samples prepared with bran from rice, barley, and wheat, respectively.

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.

Characterization of the Key Aroma Compounds in the Crust of Soft Pretzels by Application of the Sensomics Concept

Soft pretzels show a uniform brown crust color and elicit a characteristic aroma that is clearly different from those of other small types of bread. Data on the odorants responsible for this unique aroma are scarcely available. Application of aroma extract dilution analysis (AEDA) on an extract (distillate) obtained from the crust of freshly baked soft pretzels followed by identification experiments revealed 4-hydroxy-2,5-dimethyl-3(2 H)-furanone (4-HDF, caramel-like) and 2-acetyl-1-pyrroline (2-ACPY; roasty, popcorn-like), which had the highest flavor dilution (FD) factors among the 28 odor-active compounds identified. Quantitation of all 28 aroma compounds by stable isotope dilution assays (SIDA) and calculation of odor activity values (OAV) confirmed 2-ACPY, 4-HDF, and phenylacetic acid as key contributors to the pretzel aroma profile. Compared with other pastry crusts, in particular, the low odor activities of the Strecker aldehydes 2- and 3-methylbutanal, the lipid degradation product ( E)-2-nonenal, and the lack of pyrazines were elucidated as the main reasons for the different aroma profile of pretzel crust. An aroma recombinate, which is among the first established for the crusts of breads and pastries, clearly mimicked the overall odor of the pretzel crust, in particular when a solution in ethanol was sprayed in the ambient air.

Characterization of the aroma release and perception of white bread during oral processing by gas chromatography-ion mobility spectrometry and temporal dominance of sensations analysis

The purpose of this study was to investigate the aroma release and perception from white bread during oral processing by gas chromatography-ion mobility spectrometry (GC-IMS) and dynamic sensory evaluation of temporal dominance of sensations (TDS). TDS curves indicated that two maximum aroma perception signals, fermentation-like and flour-like attributes, were perceived at the beginning and swallowing, respectively. The fermentation-like, flour-like, and sour attributes were the 3 dominant aromas during oral processing. A total of 35 volatile compounds were detected in the mouth cavity during chewing white bread, 19 of them were confirmed and quantified by using the respective external standard. Based on PLSR analysis, 8 aroma compounds were predicted as potent odorants contributing to the aroma perception from chewing white bread. By application of odor activity values analysis and addition experiments, ethyl butanoate, butyl acetate, hexanal, 3-(methylthio)-propanal, 3-methylbutanal, and 2,3-butanedione were confirmed as the key odorants contributing to the aroma perception during chewing of white bread.

Recent practical researches in the development of gluten-free breads

Wheat bread is consumed globally and has played a critical role in the story of civilization since the development of agriculture. While the aroma and flavor of this staple food continue to delight and satisfy most people, some individuals have a specific allergy to wheat or a genetic disposition to celiac disease. To improve the quality of life of these patients from a dietary standpoint, food-processing researchers have been seeking to develop high-quality gluten-free bread. As the quality of wheat breads depends largely on the viscoelastic properties of gluten, various ingredients have been employed to simulate its effects, such as hydrocolloids, transglutaminase, and proteases. Recent attempts have included the use of redox regulation as well as particle-stabilized foam. In this short review, we introduce the ongoing advancements in the development of gluten-free bread, by our laboratory as well as others, focusing mainly on rice-based breads. The social and scientific contexts of these efforts are also mentioned.

Effect of selected strains on physical and organoleptic properties of breads

The use of selected Saccharomyces cerevisiae PS7314, Lactobacillus rossiae NOS7307, Lactobacillus brevis NOS7311, and Lactobacillus plantarum NOS7315 as mono-culture or co-culture for production of sourdoughs, their breads showed different physical and organoleptic properties. The pH of breads fermented with sourdoughs incubated with mono-culture or co-culture all decreased. An opposite trend was found for TTA. The use of single lactobacillus for the dough fermentation decreased the specific volume of bread, which was 4.15-19.10% lower than that of control bread (CB). However, the synergetic fermentation helped the improvement of bread quality. Compared to CB, the mixed culture 4 sourdough remarkably decreased the hardness by 52.08%, increased the specific volume by 5.29%, improved porosity of final product by 24.90%, and gave a preferable sensory characteristic to bread. Thus, the MC4 could be recommended for replacing spontaneous sourdough for improving the quality of bread.

Health risk assessment of acrylamide in bread in Iran using LC-MS/MS

Acrylamide is a chemical, often present in bread, legally classified as carcinogen, mutagen and reproductive toxicant. Since bread is consumed both world-wide and in Iran, determination of acrylamide in different types of breads is of high interest. In the present study, acrylamide was monitored in 56 Sangak and 30 industrial bread samples collected from Tehran and Shiraz, using LC-MS/MS (LOQ = 1 ng/g). In addition, the noncarcinogenic risk (target hazard quotient-THQ) and carcinogenic risk (incremental lifetime cancer risk-ILCR) due to ingestion of acrylamide through bread consumption in children and adults were assessed. Acrylamide was detected in more than 90% of the samples tested. The average daily intake of acrylamide in Iran based on exclusive consumption of Sangak bread, was estimated at 145 ng/kg bw/day. Based on the THQ for bread acrylamide in adults and children, the decreasing risk order was: Shiraz semi-industrial Sangak, Shiraz traditional Sangak, Tehran traditional Sangak, Tehran industrial bread. The ILCR of bread acrylamide calculated for adults and children was higher than the permissible lifetime carcinogenic risk value established by USEPA (1.00E-5). Results show that bread is a major source of acrylamide intake by people in Iran and all consumers regardless of age could be at elevated carcinogenic risk.

Volatile profiles of fresh rice noodles fermented with pure and mixed cultures

The volatile profiles of fresh rice noodles (FRN) fermented with pure and five commercial mixed cultures were studied by using solid phase micro extraction/ gas chromatography-mass spectrometry, electronic nose, and sensory evaluations. The main volatile compounds of FRN by pure culture included aldehydes represented by nonanal, octanal, and 2,4-Pentadienal, and alcohols represented by hexanol and 1-nonanol. Its aroma profiles showed remarkable changes during the storage time from 0 to 30 h, indicating the reduction in aldehydes and the increase in alcohols and isoamyl alcohol. Significant variations such as the types, relative amounts, and category distributions of volatile compounds were observed in FRN by five mixed cultures. The bacterial compositions of these mixed cultures were quite different, which might be responsible for the significant variations in volatile profiles. Principal component analysis on E-nose data demonstrated that FRN by Culture A, B, and C shared similar flavor, while FRN by Culture D and E possessed different aroma compared to the above three. FRN produced with pure fermentation showed the highest score in sensory evaluation, whereas FRN by mixed cultures indicated rice fragrance, light fragrance, peculiar smell, or foul smell.

Effects of Maillard Reaction Products on Sensory and Nutritional Qualities of the Traditional French Baguette

The goals of this study were to evaluate the effect of baking time on the Maillard reaction products (MRPs) generated in the crust of the traditional French baguette and to estimate their impact on its sensory characteristics, its acrylamide content, and its bifidogenic effect. Melanoidins, volatile compounds, and acrylamide were evaluated in the crust of traditional French baguettes baked between 12 and 22 min at 225 °C. The increase in melanoidins was positively correlated to the baking time, while volatile compounds only increased until 18 min. The acrylamide content was estimated to be below 18 μg/kg, which confirms the findings of EFSA that bread is not a main contributor to dietary acrylamide. A descriptive sensory analysis showed that the baking time positively affected the sensory quality of the crust. The consumer test revealed the same trend and the panelists favorably judged the well-baked baguettes based on a better crust flavor and crispness. The bifidogenic effect of the crust and the crumb from the baguettes baked 22 min was evaluated on the in vitro growth of Bifidobacterium adolescentis. The results demonstrated that the crumb and the crust had exactly the same bifidogenic impact, therefore not caused by melanoidins.

PRACTICAL APPLICATION

The consumption of bread in France has decreased since 2007, although bread is considered by French people as "healthy" and essential to maintain a balanced diet. The current study evaluated the global qualities of the French baguette in order to highlight its high sensory quality and its beneficial effect by inducing a possible growth of bifidobacteria, even in well-baked baguettes. These findings allow the French bakery industry to develop an argument to promote its technical know-how and to help consumers choose healthier and tastier bread. Moreover, this study provided some recommendations of baking processes to maintain a high sensory quality of the French baguette and limit the formation of undesirable compounds, such as acrylamide, in the crust.