Influence of endogenous ferulic acid in whole wheat flour on bread crust aroma

Mechanisms of flavonoid inhibition of Maillard reaction product formation in relation to whole grains processing

Whole grains (WG) are beneficial to health but have reduced sensory quality, partly attributable to inhibition of Maillard reaction products (MRP) by WG phenolics. The study investigated how major flavonoid classes in cereals affect Maillard reaction pathways. Flavonoids were reacted with xylose-lysine aqueous system at 160 °C/12 min. Additionally, breads were made with catechin, and wheat and sorghum bran fortification. Low Mw MRP were profiled using UPLC-MS/MS, while melanoidins were characterized using fluorescence spectroscopy and HPSEC-MALS. The flavonoids significantly (p < 0.05) reduced both melanoidin content (by 33-86%) and Mw (3.5-15 kDa vs 20 kDa control), leading to lighter bread crust. Flavonoids inhibited MRP via direct condensation with early-stage amines and carbonyls into stable adducts, and reduction of late-stage polymerization reactions, increasing accumulation of cyclic N-containing intermediates. Inhibitory trend was flavones>flavanones>flavanols. C-Ring π-bond dramatically enhance flavonoid MRP inhibition; thus flavone-rich cereal grains are likely to strongly impact MRP-dependent sensory attributes of WG products.

Modelling of perceived sweetness in biscuits based on sensory analysis as a new tool to evaluate reformulation performance in sugar reduction studies

Sugar reduction in foods is of global interest in food science and industry to limit excessive calorie intake for healthier nutrition. Therefore, a modified Weibull model-based approach is presented here to relate sweetness perception with sugar concentration for the first time. The model was tested by using sweetness perception data obtained from sensory analysis of biscuits (wholewheat flour, whey or hydrolysed pea protein, different sucrose forms, ethylvanillin, furaneol, phenylacetaldehyde) using a line scale and untrained panellists. Sweetness scores increased 56%, 59%, 41% by the addition of wholewheat flour, proteins, or aroma compounds at 17% sucrose containing biscuits, respectively. Wholewheat flour and proteins boosted Maillard reaction products imparting baked/caramel-like flavour. The Weibull model well fitted to the sweetness perception data with a sigmoidal curve and high predicting power. This approach allows to explain how much sugar reduction can be achieved to reach a targeted sweetness perception without performing further sensory analysis.

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.

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.

Incorporation of polyphenols in baked products

Bakery foods, including breads, cakes, cookies, muffins, rolls, buns, crumpets, pancakes, doughnuts, waffles, and bagels, etc., have been an important diet of humans for thousands of years. As the nutraceuticals with various biological activities, polyphenols, especially polyphenol-enriched products are widely used in bakery foods. The polyphenol-enriched products are mainly from fruits and vegetables, including fruits in whole, juice, puree, jam, and the powder of dried fruits, pomace, and peels. Incorporation of these products not only provide polyphenols, but also supply other nutrients, especially dietary fibers for bakery products. This chapter discussed the thermal stability of different types of polyphenols during baking, and the effect of polyphenols on the sensory attributes of baked foods. Moreover, their role in mitigation of reactive carbonyl species and the subsequent formation of advanced glycation end products, antioxidant and antimicrobial activities have been also discussed. Since polyphenols are subjected to high temperature for dozens of minutes during baking, future works need to focus on the chemical interactions of polyphenols and their oxidized products (quinones) with other food components, and the safety consequence of these interactions.

Rapid, High-Throughput Quantitation of Odor-Active 2-Acetyl Azaheterocycles in Food Products by UHPLC-MS/MS

A rapid, high-throughput method for the quantitation of the 2-acetyl azaheterocycles, 2-acetyl-1-pyrroline, 2-acetyl-1,4,5,6-tetrahydropyridine, 2-acetylpyrazine, and 2-acetyl-2-thiazoline, in different food products, by liquid chromatography-tandem mass spectrometry (LC-MS/MS), was developed. The quick extraction by bead beater homogenization, fast derivatization by 3-nitrophenylhydrazine (40 °C, 2 h), and efficient LC separation make this method suitable for high-throughput analysis. As established in this study, the highly precise LC-MS/MS method applies to different food products or beverages without requiring further adjustment. The analysis was performed with sample amounts of 0.2-0.5 g, and limit of quantitation values of 0.6, 0.5, 0.6, and 1.0 μg/kg were obtained for 2-acetyl-1-pyrroline, 2-acetyl-1,4,5,6-tetrahydropyridine, 2-acetylpyrazine, and 2-acetyl-2-thiazoline, respectively. Thus, it was possible to quantitate the analytes in the range of their odor thresholds.

Characterization of the Key Aroma Constituents in Fry Breads by Means of the Sensomics Concept

The key aroma constituents in the volatile fractions isolated FROM two differently processed fry breads by solvent-assisted flavor evaporation were characterized by an aroma extract dilution analysis (AEDA). Twenty-two compounds were identified with flavor dilution (FD) factor ranges of 2–516. Among them, 13 compounds (FD ≥ 16) were quantified by stable isotope dilution assays and analyzed by odor activity values (OAVs). Of these, 11 compounds had OAVs ≥ 1, and the highest concentrations were determined for δ-decalactone and 2,3-butanedione. Two recombination models of the fry breads showed similarity to the corresponding fry breads. Omission tests confirmed that aroma-active constituents, such as δ-decalactone (oily/peach), 2-acetyl-1-pyrroline (roasty/popcorn-like), 3-methylbutanal (malty), methional (baked potato-like), 2,3-butanedione (buttery), phenyl acetaldehyde (flowery), (E,E)-2,4-decadienal (deep-fried), butanoic acid, and 3-methylbutanoic acid, were the key aroma constituents of fry bread. In addition, 3-methoxy-4-vinylphenol (smoky) and 4-hydroxy-2,5-dimethyl-3(2H)-furanone were also identified as important aroma constituents of fry bread.

Identification of Aroma Differences in Refined and Whole Grain Extruded Maize Puffs

Differences in the aroma profiles of extruded maize puffs made from refined grain and whole grain flour were investigated. Gas chromatography/mass spectrometry/olfactometry (GC/MS/O) analysis reported 13 aroma compounds with a flavor dilution (FD) value ≥16. Quantitative analysis identified eight compounds as statistically different, of which seven compounds were higher in concentration in the whole grain sample. Sensory recombination and descriptive analysis further supported the analytical data, with higher mean aroma intensities for cooked, corn chip, roasted, and toasted attributes for the whole grain sample. Generally, the compounds responsible for perceived differences in whole grain maize extruded puffs were associated with increased levels of Maillard reaction products, such as 2-ethyl-3,5-dimethylpyrazine and 2-acetyl-2-thiazoline.

Comparison of the Aroma Profiles of Intermediate Wheatgrass and Wheat Bread Crusts

The aroma profiles of bread crusts made from intermediate wheatgrass (Thinopyrum intermedium) and whole wheat (Triticum aestivum) flours were compared. Based on gas chromatography/mass spectrometry/olfactometry analysis, twenty-four odorants were identified and further quantified. The concentrations of seventeen compounds were significantly different between intermediate wheatgrass and whole wheat bread crusts, of which sixteen compounds were higher in the whole wheat sample. The aroma profiles of the bread samples were subsequently characterized using sensory descriptive analysis (DA) and indicated that the roasted attribute was perceived at a significantly higher intensity in the whole wheat sample due to a greater amount of Maillard reaction compounds. Alternatively, bran and green notes were perceived at higher intensities in the intermediate wheatgrass sample, however they were not attributed to the presence of specific compounds but rather to a change in the aroma composition. Aroma recombination DA of the whole wheat and intermediate wheatgrass aroma models was similar to the original aroma profiles of the bread samples, demonstrating the sensory relevance of the identified odorants.

Positive and negative effects of polyphenol incorporation in baked foods

Polyphenols are hot research topics worldwide owing to their physiological and pharmaceutical activities. Polyphenols and polyphenol-enriched by-products have been widely used in bakery foods because of their neutraceutical properties. This review summarizes the classification, biosynthesis, main source and analysis of polyphenols and intensively discusses the effects of their incorporation in baked foods. The positive effects of polyphenol incorporation include elevation of antioxidant activity of baked foods, scavenging of food-borne toxins produced during thermal processing and decreasing postprandial serum glucose level. Meanwhile, polyphenol incorporation negatively influences colour, texture and flavour of baked foods and bioavailability of the added polyphenols. Most polyphenols are thermally sensitive and reactive. Thus far, few studies have investigated on neoformed compounds from the reaction of polyphenols or their oxidised products (quinones) with other food components. Before launching polyphenol-incorporated bakery foods in the market, future work should focus on full toxicological evaluation of newly derived compounds from polyphenols.

Analysis of volatile compounds in gluten-free bread crusts with an optimised and validated SPME-GC/QTOF methodology

The aroma of bread crust, as one of the first characteristics perceived, is essential for bread acceptance. However, gluten-free bread crusts exhibit weak aroma. A SPME-GC/QTOF methodology was optimised with PCA and RSM and validated for the quantification of 44 volatile compounds in bread crust, extracting 0.75 g of crust at 60 °C for 51 min. LODs ranged between 3.60 and 1760 μg Kg^-1, all the R² were higher than 0.99 and %RSD for precision and %Er for accuracy were lower than 9% and 12%, respectively. A commercial wheat bread crust was quantified, and furfural was the most abundant compound. Bread crusts of wheat starch and of japonica rice, basmati rice and teff flours were also quantified. Teff flour and wheat starch crusts were very suitable for improving gluten-free bread crust aroma, due to their similar content in 2-acetyl-1-pyrroline and 4-hydroxy-2,5-dimethyl-3(2H)-furanone compared to wheat flour crust and also for their high content in pyrazines.

Volatile Organic Compounds at Early Stages of Sourdough Preparation Via Static Headspace and GC/MS Analysis

Major aroma volatile compounds from whole wheat and all-purpose sourdough and their evolution were evaluated through static headspace gas chromatography-mass spectrometry (SHS-GC/MS) analysis during 28 days of fermentation. Sourdoughs were prepared on 1:1 ratio of flour to water (mass to volume) and fermented spontaneously at room temperature. GC/MS measurements for the evolution of aroma volatile compounds were conducted at 24, 168, 336, 504, and 672 hours of fermentation. Whole wheat sourdough contained more aroma volatile compounds (62) than all-purpose sourdough (45). The major aroma volatile compounds of whole wheat sourdough were hydrocarbons, esters, alcohols, ketones, aldehydes, and heterocycles. Meanwhile, aldehydes were dominant in the all-purpose sourdough. During whole wheat sourdough fermentation, a decrease in peak area percent was observed for aldehydes, ketones, and heterocycles, whereas an increase in the case of hydrocarbons. On the other hand, aldehydes dramatically increased in peak area percent for all-purpose sourdough. Aroma volatile compounds emanating from sourdough fermentation can aid consumers as well as manufacturers with regards to the quality, shelf-life, and what characteristic aromas the final bread product will possess.

Volatile compounds in whole meal bread crust: The effects of yeast level and fermentation temperature

The influence of fermentation temperatures (8°C, 16°C, and 32°C) and yeast levels (2%, 4%, and 6% of the flour) on the formation of volatile compounds in the crust of whole meal wheat bread was investigated. The fermentation times were regulated to optimum bread height for each treatment. The volatile compounds were extracted by dynamic headspace extraction and analyzed by gas chromatography-mass spectrometry. The results were evaluated using multivariate data analysis and ANOVA. In all crust samples 28 volatile compounds out of 58 compounds were identified and the other 30 compounds were tentatively identified. Higher fermentation temperatures promoted the formation of Maillard reaction products 3-methyl-1-butanol, pyrazine, 2-ethylpyrazine, 2-ethyl-3-methylpyrazine, 2-vinylpyrazine, 3-hydroxy-2-butanone, 3-(methylsulfanyl)-propanal, and 5-methyl-2-furancarboxaldehyde whereas at lower temperature (8°C) the formation of 2- and 3-methylbutanal was favored. Higher levels of yeast promoted the formation of 3-methyl-1-butanol, 2-methyl-1-propanol and 3-(methylsulfanyl)-propanal, whereas hexanal was promoted in the crust fermented with lower yeast level.

Analytical methods for volatile compounds in wheat bread

Bread aroma is one of the main requirements for its acceptance by consumers, since it is one of the first attributes perceived. Sensory analysis, crucial to be correlated with human perception, presents limitations and needs to be complemented with instrumental analysis. Gas chromatography coupled to mass spectrometry is usually selected as the technique to determine bread volatile compounds, although proton-transfer reaction mass spectrometry begins also to be used to monitor aroma processes. Solvent extraction, supercritical fluid extraction and headspace analysis are the main options for the sample treatment. The present review focuses on the different sample treatments and instrumental alternatives reported in the literature to analyse volatile compounds in wheat bread, providing advantages and limitations. Usual parameters employed in these analytical methods are also described.

Reactive carbonyl-scavenging ability of 2-aminoimidazoles: 2-amino-1-methylbenzimidazole and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)

The carbonyl-scavenging ability of 2-amino-1-methylbenzimidazole (AMBI) and the heterocyclic aromatic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was investigated in an attempt to identify new routes that can modify the carbonyl content of foods. The reaction of both AMBI and PhIP with 2-alkenals, 2,4-alkadienals, 4-oxo-2-alkenals, 4,5-epoxy-2-alkenals, and 4-hydroxy-2-nonenal produced fluorescent adducts, whose structure was determined for the adduct produced between AMBI and 2-pentenal. This adduct was isolated and identified by one- and two-dimensional nuclear magnetic resonance and high-resolution mass spectrometry as 2,10-dihydro-2-ethyl-10-methylpyrimido[1,2-a]benzimidazole. The formation of these adducts was parallel to the elimination of AMBI and PhIP. The Ea of the reaction between PhIP and 4-oxo-2-nonenal was 27.4 kJ/mol. All these results suggest that 2-aminoimidazoles can be employed to modify the carbonyl content of foods. At the same time and because the reaction produces the disappearance of the amino compound, lipid-derived carbonyl compounds can be employed to eliminate 2-aminoimidazoles, which suggests a new strategy for the elimination of heterocyclic aromatic amines in foods.