Cereal Safety and Quality in Malting and Brewing Industries

Kristina Mastanjević, Vinko Krstanović & Krešimir Mastanjević

Josip Juraj Strossmayer University of Osijek, Faculty of Food Technology Osijek, Croatia

*Correspondence to: Dr. Kristina Mastanjević, Josip Juraj Strossmayer University of Osijek, Faculty of Food Technology Osijek, Croatia.

Copyright © 2018 Dr. Kristina Mastanjević, et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

General Requirements Regarding Malting Cereals
There are strict recommendations and legal limits regarding satisfactory barley quality intended for malting and brewing (protein content, β-glucan content, Kolbach index, malt extract, extract difference, saccharification time, wort colour, viscosity, FAN (free amino nitrogen) etc. However, protein content if far most important indicator of quality, deciding on the initial acceptance of cereals in the malt factory. Optimal protein content is below 12%. Higher amounts result in heighten soluble proteins content in wort which leads to off-flavours in beer. Protein content < 11% usually means lower extract values [1]. This reflects poorly to the fermentation process because of the poor amino acid content available for yeast nutrition. β-glucans can also act as a limiting factor in malting and brewing.

In recent research attention has been paid to β-glucans because of their beneficial effects on human health since they can be characterised as prebiotics [2]. However, brewers label β-glucans as not desirable in cereals intended for malting and brewing. Total β-glucan content in barley normally ranges from 2 to 8% [3], with the acceptable level for brewing being < 4% (MEBAK; EBC). Even though there are no recommendations for total β-glucan content in malt, according to Davis (2006) [9], β-glucan values in wort should be kept below 200mg/L. β-glucans in cereals principally depend on genetic factors, but climatic conditions, agro technical measures, soil type also influence the total β-glucan content in barley [5-7]. Not to be all negative about β-glucans, in the right amount they are considered useful for brewing, because they do contribute to the beer foam stability and improve beer organoleptic properties (i.e. beer mouth feels) [8]. During malting, high β-glucan content can lead to unsatisfactory cell wall degradation, disrupting the germination and reducing malt extract which means less sugars for yeast during fermentation [9]. Other negative consequence of β-glucan residues in malt is poor mash conversion, highly viscous wort and difficulties during the filtration process [9,10]. All this conditions the acceptable low to moderate β-glucans content in cereals intended for malting [10]. Wheat is used in malting and brewing to a much lesser extent and the recommendations for malting wheat are not as strict as for barley. Only 0.5% of wheat ends up in beer, in oppose to barley where 16% of world’s production is provided for malting [11,12]. Wheat is usually used in production of special beer and whiskey malts.

Fusarium Infections and Mycotoxins Occurrence in Malting and Brewing Industries
Good quality raw material is the most important factor in malting and brewing industry. Pathogenic fungi belonging to Fusarium spp. can cause great degradation of malt grain quality. Most important species causing FHB in Central and Northern Europe are F. avanceum, F. graminearum, F. poae and F. culmorum (WG Smith) Sacc. [13,14]. Because they thrive in malting process conditions (high moisture, low temperature, high nutritive values of grains), Fusarium fungi are considered one of the most important indicators of cereal quality. They are ability to degrade endosperm, as they integrate into the grain. Fusarium fungi reduce 1000 kernel weight, test weight, increase moisture content, prolong saccharification time and speed of filtration, increase total protein and total nitrogen content, increase soluble protein and soluble nitrogen content [11,15]. Congress wort colour, colour after cooking, viscosity, free amino nitrogen (FAN) and pH value are highly important indicators of malt quality. In case of Fusarium infection they are prone to deteriorate and as such influence beer quality [15].

Gushing is a phenomenon best described as sudden overfoaming of beer on opening the container (can, bottle). Gushing is in direct linkage with proteins called hydrophobins. Hydrophobins are a product of fungal metabolism, and are also found in Fusarium fungi [16]. Overfoaming serves as an indicator of malt quality and causes economic problems for breweries [17].

Mycotoxins are secondary metabolites of Fusarium fungi and are also considered quality indicators of cereals prior their entrance into the malting factory. Fusarium fungi produce these toxic compounds that represent health hazard not only for humans but for animals too. Several hundred mycotoxins [18], about 200 of which belong to trichothecenes group [19] have been classified so far. High temperatures applied during malting (drying phase) and cooking (beer) do not act degrading to mycotoxins and this is why they are such an important topic in brewing industry [20,21]. Today’s brewing is a global industry, meaning that a few big breweries are taking the major piece of the market. However, small, home-brewers and craft breweries are very popular.

Mycotoxins levels should be monitored in order to avoid health safety issues. Even casual beer-drinkers (up to 2 beers per day, or up to 1L of beer), according to Warth et al. (2012) [12] can exceed the PMTDI (provisional maximum tolerable daily intake) for DON (1μg/kg bw/d), and similar can be expected for other mycotoxins found in beer. Filtration is by tradition, for some types of wheat beers, an omitted unit operation, meaning that yeast remains active during storage and changes beer profile (aroma, body and taste). Many studies dealt with mycotoxins in commercial and craft beers [22-25], and results showed that mycotoxins (deoxynivalenol (DON), nivalenol, T-2, HT-2, diacetoxyscirpenol, zearalenone, aflatoxins, ochratoxin A, and fumonisins) do occur in beers, but in very low concentrations (mostly <1µg/L).

Malting and Brewing By-Products
Malting and brewing by-products represent a nutritious and valuable, low-cost source of feed for livestock and additives for food industry [26,27]. By-products derived from the malting and brewing processes, such as germ/rootlets, spent grains and spent yeast are rich in proteins, digestible fibre material, vitamins and minerals. However, the above-mentioned by-products can also be contaminated with mycotoxins [21,27]. Habschied et al. (2011) [28] and Krstanović et al. (2015) [21] conducted a research where the highest concentrations of DON and ZEA were found in germ/rootlets fraction.

Brewing and malting by-products can also be used directly (spent grains can be utilized in snacks production or bread) or as supplements in human nutrition [29]. Mussatto et al. (2006) [26] proposed the use of brewer’s grain flour in manufacture of flakes, whole-wheat bread, biscuits and aperitif snacks. Zechner-Krpan et al. (2014) [30] investigated the use of β-glucan from spent yeast in food industry, and the positive biological effects of β-glucan in human body have been previously described [31].

Brewer’s spent grains (BSG) are obtained after the filtration of mash and represent a moist brewing by-product that is used as animal feed in form of fresh (wet), ensiled or dehydrated (dried) grain, depending on the type of the animal. Spent grains are often mixed with hot trub, another by-product of brewing process. Hot trub is the result of precipitation of boiled wort after hopping. It is mostly formed of high molecular, insoluble proteins, which coagulate during cooking with hops, and, mixed with spent grains, adds nutritive value to animal food [32]. Implementation of spent yeast into the brewing process is also possible. According to Mussatto et al. (2006) [26], BSG extract can be utilized as an antifoaming agent in brewing process. Brányik et al., (2001) [33] described the use of BSG’s irregularly shaped particles and their active centers as a mean to immobilize yeast cells and to re-emerge them into the brewing process. There are many possibilities for use of BSG in different biotechnological processes, detailed in a review by Solange & Mussatto (2014) [34]. Spent yeast is a final by-product, taken after the fermentation and filtration of beer. Due to its high moisture content, spent yeast also has to be subjected to additional processes, i.e. drying, in order to inactivate the living yeast cells because ruminants have a complex mixture of micro flora to help breakdown the cellulose into simpler carbohydrates they can use for energy. Small amounts of live yeast can be safe for ruminants, but higher amounts can lead to a gas build up. This can block ruminants’ air passage causing suffocation or even death [35]. Brewer’s spent yeast (BSY) can be re-used several times (usually four - six generations), and its biomass represents the second major by-product in brewing industries [36]. The re-use of BSY in breweries is a very common practice since it is much faster than propagation.

Conclusion

Today’s demands for safe and healthy food is increasing and the number of consumers who are willing to educate themselves on this subject set the bar high for good food on the market. Institutions monitor every aspect of food industry and every day new analytical techniques and methods are being developed in order to determine lower and lower levels of harmful and nutritive compounds that directly or indirectly - via animal products, effect human health in a positive or negative manner. Today’s industries are prone to prevent every possibility of economic losses and health safety issues before the raw material acceptance into the malting or brewing factory.

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