Starch contributes to barley grain and malt quality which in turn contributes to beer quality and flavour; through fermentable sugar profiles, rates of fermentation and Mallard reactions. Both ...amylopectin and amylose are enzymatically degraded to release maltose, maltotriose and higher order sugars.
Amylopectin is highly branched α-(1 → 6) glycoside bond branch points with numerous short branches while amylose is a long chained polymer with a few side branches. During grain development, the final level of branching is controlled by two enzymes namely; isoamylase and limit dextrinase (LD). Mutations in either of these genes can also result in changes to structure, content, and granule formation and size. During the malting free LD will to cleave the α-(1 → 6) bonds but during mashing processes, bound LD is release, resulting in chains of various length available for other starch degrading enzymes to hydrolyse.
While there is a good understanding of most of the individual aspects in amylopectin formation, structure and degradation; the story remains incomplete, as most of this understanding has been gained from experiments with only a limited number of barley varieties, limitations in the technology for structural measurement, and since no data is available to link structure to fermentable sugar profiles.
•Amylopectin is the most abundant polymer in barley.•Amylopectin is highly branched as a results of branching and debranching enzymes.•Limit dextrinase is one of the debranching enzymes.•Limit dextrinase acts during grain filling and post-harvest germination.•The role of limit dextrinase in both these modes is yet to be clearly defined.
Beer has over 600 flavor compounds and creates a positive tasting experience with acceptable sensory properties, which are essential for the best consumer experience. Spontaneous and mixed-culture ...fermentation beers, generally classified as sour beers, are gaining popularity compared to typical lager or ale styles, which have dominated in the USA for the last few decades. Unique and acceptable flavor compounds characterize sour beers, but some unfavorable aspects appear in conjunction. One such unfavorable flavor is called “mousy”. This description is usually labeled as an unpleasant odor, identifying spoilage of fermented food and beverages. It is related as having the odor of mouse urine, cereal, corn tortilla chips, or freshly baked sour bread. The main compounds responsible for it are N-heterocyclic compounds: 2-acetyltetrahydropyridine, 2-acetyl-1-pyrroline, and 2-ethyltetrahydropyridine. The most common beverages associated with mousy off-flavor are identified in wines, sour beers, other grain-based beverages, and kombucha, which may contain heterofermentative lactic acid bacteria, acetic acid bacteria, and/or yeast/fungus cultures. In particular, the fungal species Brettanomyces bruxellensis are associated with mousy-off flavor occurrence in fermented beverages matrices. However, many factors for N-heterocycle formation are not well-understood. Currently, the research and development of mixed-cultured beer and non/low alcohol beverages (NABLAB) has increased to obtain the highest quality, sensory, functionality, and most notably safety standards, and also to meet consumers’ demand for a balanced sourness in these beverages. This paper introduces mousy off-flavor expression in beers and beverages, which occurs in spontaneous or mixed-culture fermentations, with a focus on sour beers due to common inconsistency aspects in fermentation. We discuss and suggest possible pathways of mousy off-flavor development in the beer matrix, which also apply to other fermented beverages, including non/low alcohol drinks, e.g., kombucha and low/nonalcohol beers. Some precautions and modifications may prevent the occurrence of these off-flavor compounds in the beverage matrix: improving raw material quality, adjusting brewing processes, and using specific strains of yeast and bacteria that are less likely to produce the off-flavor. Conceivably, it is clear that spontaneous and mixed culture fermentation is gaining popularity in industrial, craft, and home brewing. The review discusses important elements to identify and understand metabolic pathways, following the prevention of spoilage targeted to off-flavor compounds development in beers and NABLABs.
•Barley starch structural changes during malting are investigated.•Both starch amylose and amylopectin are hydrolyzed during malting.•Protein retards starch hydrolysis in mashing by inhibiting ...granule swelling.•Barleys with more short-chain amylose molecules release more fermentable sugars.•Starch molecular structure is useful for determining fermentable sugars production.
Ten barley samples containing varied protein contents were subject to malting followed by mashing to investigate molecular effects of both barley starch and starch- protein interactions on malting and mashing performances, and the underlying mechanism. Starch granular changes were examined using differential scanning calorimetry and scanning electron microscopy. The molecular fine structures of amylose and amylopectin from unmalted and malted grain were obtained using size-exclusion chromatography. The results showed that both amylose and amylopectin polymers were hydrolyzed at the same time during malting. Protein and amylose content in both unmalted and malted barley significant negatively correlated with fermentable sugar content after mashing. While protein content is currently the main criterion for choosing malting varieties, this study shows that information about starch molecular structure is also useful for determining the release of fermentable sugars, an important functional property. This provides brewers with some new methods to choose malting barley.
Barley is an important cereal grain used for beer brewing, animal feed, and human food consumption. Fungal disease can impact barley production, as it causes substantial yield loss and lowers seed ...quality. We used sequential window acquisition of all theoretical ions mass spectrometry (SWATH-MS) to measure and quantify the relative abundance of proteins within seeds of different barley varieties under various fungal pathogen burdens (ProteomeXchange Datasets PXD011303 and PXD014093). Fungal burden in the leaves and stems of barley resulted in changes to the seed proteome. However, these changes were minimal and showed substantial variation among barley samples infected with different pathogens. The limited effect of intrinsic disease resistance on the seed proteome is consistent with the main mediators of disease resistance being present in the leaves and stems of the plant. The seeds of barley varieties accredited for use as malt had higher levels of proteins associated with starch synthesis and beer quality. The proteomic workflows developed and implemented here have potential application in quality control, breeding and processing of barley, and other agricultural products.
•Fungal infection in barley leaves affects the seed proteome.•Malt accredited barley varieties have high levels of starch synthesis proteins.•Proteomic workflows will be useful in barley quality control, breeding, and processing.
•β-glucan is an important nutritional component of oats.•Starch structure also important for food energy and digestibility.•Swelling power, pasting properties and hardness are food functional ...properties.•The relations between these, β-glucan and starch structure is examined.•The results show how grains may be selected for improved functional properties.
Wheat flour noodles are sometimes fortified with β-glucan for nutritional value, but this can decrease eating quality. The contributions of β-glucan and starch molecular fine structure to physicochemical properties of wholemeal oat flour and to the texture of oat-fortified white salted noodles were investigated here. Hardness of oat-fortified noodles was controlled by the longer amylopectin chains (DP ≥ 26) and amount of longer amylose chains (DP ≥ 1000). Higher levels of β-glucan, in the range from 3.1 to 5.2%, result in increased noodle hardness. Pasting viscosities of wholemeal oat flour positively correlate with the hardness of oat-fortified noodles. The swelling power of oat flour is not correlated with either pasting viscosities of oat flour or noodle hardness. Longer amylopectin chains and the amount of longer amylose chains both control the pasting viscosities of oat flour, which in turn affect noodle texture. This provides new means, based on starch and β-glucan molecular structure, to choose oats with optimal starch structure and β-glucan content for targeted oat-fortified noodle quality.
•Noodle-making process and cooking increase solubility of β-glucan.•β-Glucan is lost into the cooking water during cooking.•Noodle-making process and cooking do not change β-glucan molecular ...size.•Oat-fortified noodle has lower starch digestion rate than wheat noodles.•β-Glucan alters microstructure of noodles and reduces the rate of starch hydrolysis.
White wheat salted noodles containing oats have a slower digestion rate those without oats, with potential health benefits. Oat β-glucan may play an important role in this. Effects of sheeting and shearing during noodle-making and subsequent cooking on β-glucan concentration, solubility, molecular size and starch digestibility were investigated. The levels of β-glucan were reduced by 16% after cooking, due to the loss of β-glucan into the cooking water. Both the noodle-making process and cooking increased the solubility of β-glucan but did not change its average molecular size. Digestion profiles show that β-glucan in wholemeal oat flour did not change starch digestion rates compared with isolated starch, but reduced the starch digestion rate of oat-fortified wheat noodles compared to the control (wheat noodles). Confocal laser scanning microscopy suggests that interaction between β-glucan and protein contributes to the starch-protein matrix and changes noodle microstructure, and thus alters their digestibility.
The beer industry is a major producer of solid waste globally, primarily in the form of brewer's spent grain (BSG), which due to its low value has historically been diverted to livestock as feed or ...to landfills. However, its high moisture content and chemical composition positions BSG as an ideal candidate for further processing with microbial fermentation. Recent research has focused on filamentous fungi and the ability of some species therein to degrade the predominant recalcitrant cellulolignin components of BSG to produce valuable compounds. Many species have been investigated to biovalorize this waste stream, including those in the genuses
,
,
and
, which have been used to produce a wide array of highly valuable enzymes and other functional compounds, and to increase the nutritional value of BSG as an animal feed. This review of recent developments in the application of filamentous fungi for the valorization of BSG discusses the biochemical makeup of BSG, the biological mechanisms underlying fungi's primacy to this application, and the current applications of fungi in this realm.
Different methods have been applied in controlling contamination of foods and feeds by the carcinogenic fungal toxin, aflatoxin, but nevertheless the problem remains pervasive in developing ...countries. Curcumin is a natural polyphenolic compound from the spice turmeric (Curcuma longa L.) that has been identified as an efficient photosensitiser for inactivation of Aspergillus flavus conidia. Curcumin mediated photoinactivation of A. flavus has revealed the potential of this technology to be an effective method for reducing population density of the aflatoxin-producing fungus in foods. This study demonstrates the influence of pH and temperature on efficiency of photoinactivation of the fungus and how treating spore-contaminated maize kernels affects aflatoxin production. The results show the efficiency of curcumin mediated photoinactivation of fungal conidia and hyphae were not affected by temperatures between 15 and 35 °C or pH range of 1.5–9.0. The production of aflatoxin B1 was significantly lower (p < 0.05), with an average of 82.4 μg/kg as compared to up to 305.9 μg/kg observed in untreated maize kept under similar conditions. The results of this study indicate that curcumin mediated photosensitization can potentially be applied under simple environmental conditions to achieve significant reduction of post-harvest contamination of aflatoxin B1 in maize.
•Photosensitization-curcumin inactivated conidia and hyphae of Aspergillus flavus.•Conidia and hyphae inactivation of Aspergillus flavus was not affected by pH or temperature.•Photosensitization-Curcumin significantly reduced the production of aflatoxin B1 in maize kernels
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•Preharvest germinated malting barley discrimination achieved 100% classification accuracy.•VNIR and SWIR imaging using two distinct near infrared hyperspectral imaging cameras.•Novel ...multiblock approach using SO-PLS-LDA obtained 100% classification accuracy.•Significant waveband reduction using SO-CovSel-LDA, retaining classification accuracy of 97%.•The study shows an applicable method for novel multiblock spectral imaging classification.
A novel data fusion method based on the use of visible/near-infrared (VNIR) and shortwave infrared (SWIR) imaging sensors, to distinguish between pregerminated and ungerminated barley grain is proposed. Spectral imaging was used to fingerprint germinated and ungerminated barley grain from a total of 5640 average spectra representing single barley kernels varying with respect to germination time. Chemometric approaches utilising partial least squares-discriminant analysis (PLS-DA) and multiblock sequential and orthogonalized partial least squares-linear discriminant analysis (SO-PLS-LDA) and sequential and orthogonalized covariance selection-linear discriminant analysis (SO-CovSel-LDA) were used to build classification models. SO-PLS-LDA achieved a total classification rate of 99.88%, while SO-CovSel-LDA resulted in a classification accuracy of 97.46% when a maximum of 8 variables were selected from each data block (VNIR and SWIR) – models were validated on an independent test set. The use of multiblock approaches led to increased prediction accuracy, compared to PLS-DA, and a viable solution to address the industry problem to detect pregerminated malting barley in a rapid, non-destructive manner. This represents a significant advance with respect to the current dated methods which are hindered by time-consuming wet chemistry techniques and human subjective bias. The potential of the proposed new technique also has the further advantage of moving toward multispectral systems which can be used to detect pre-harvest germinated barley using an even more computationally rapid and affordable online sorting machine incorporating the wavebands of importance selected by SO-CovSel-LDA. The study highlights how sequential and orthogonalised data fusion approaches, in the food and agricultural sector, are powerful solutions to real world problems.
Two varieties of barley samples were subjected to germination conditions to investigate the underlying mechanisms underpinning changes in molecular structure, chemical compositions and thermal ...properties of starch during this process. Starch thermal transitions were examined using differential scanning calorimetry, and the molecular fine structure of amylose and amylopectin were determined using size-exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis, respectively. Both amylose and amylopectin chains were hydrolyzed during germination, but a preferential attack of amylopectin chains was observed with concomitant increases of relative amylose content, resulting in increased gelatinization temperatures (onset, peak, conclusion) and reduction in enthalpy change. Amylolytic enzyme activities increased during germination, resulting in decreased starch content. After malting, significant degradation of amylose chains followed by the reduction of gelatinization temperatures was seen. Roasting of pale malts was found to degrade starch and protein whilst completely stopping enzyme activities. The resulting coloured malts had extremely low starch enthalpy change due to the loss of amylopectin crystallinity at high temperature. This study provides insights into starch structural changes of barley throughout malting and roasting, which are determining factors for fermentable sugar production during mashing.
•Barley starch structural changes during germination are examined.•Preferential attack of amylopectin chains is observed.•Gelatinization temperatures increase and enthalpy change reduces during germination.•Kilning degrades amylose chains and reduces amylose content significantly.•High-temperature roasting stops enzyme activities and degrades amylopectin chains.
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