Evaluation and utilization of spent grains
Spent grains are produced by the extraction of malt. By the extraction of malt the
soluble parts are dissolved in water, for example starch and Sow molecular sugars.
The non-soluble parts are the spent grains The brewery spent grains {BSG} are the
dominating by-product in the brewery, besides hat trub, malt dust, etc. in beer
production, about 18 - 20 kg of wet grains are produced per hl of saleable product
Changes of phenolic compounds during fermentation
Phenolic compounds are of considerable significance in brewing. Its most important
aspect is in relation to haze formation. Simple acids are part of the numerous
substances and more highly condensed phenols with protein precipitating and reducing effect. These substances influence colour, foam, stability, flavour and taste. The main part with nearly 80% of these substances comes from the malt, the rest from the hops. The water can also contain such connections but only in very small quantities. Hop extract contains no phenolic compounds; therefore none of these substances can reach into the wort. The use of phenol reduced barley like proanthocyanidin-free barley also leads to a clear reduction of these connections. The effects of these substances on the beer quality are known but there are discrepancies about its meaning in the positive and negative meaning. The low molecular compounds are very strong antioxidants and being able to offer protection against oxidation through it. This has to be judged to be positive. Other groups are directly or indirectly involved in the taste behaviour. This can also be positive and negative. The most important property is their ability to build hydrogen bridges with proteins or with other phenols what can be lead to haze formations.
Phospates in malt
Phosphate is a mineral and compared to the other compounds of barley is the amount
of minerals pretty low. But the minerals are important for the metabolism of plants (very useful while malting) and for some brewing technical matters later on. Zinc, for instance, is responsible for a healthy and active yeast, oxalates for beerstone and especially the phosphates are involved with the pH-value in mash, wort and final beer. Minerals in wort are almost completely influenced by the malt and neglectable by the brewing liquor. Admitted, the brewing process itself has a certain influence to the mineral content in wort (eg amount of sparge liquor), but it still depends mainly on the malt. Phosphates have the property to accept or to donate, up to a certain point of course, H+-ions or other protons. That means, they can react both as an acid as well as a caustic. This function is also called buffer effect.
Specifications of the delivery of barley to maltsters and of malt to brewers
As it is known, barley and its product malt is one of the main raw material for the brewing process. Both, maltsters and brewers, are interested in getting the best available material to harm possible occurring problems during processes like lautering, filtration, and so on. For example it has been shown that the malt raw material is one of the main causes of filtration problems. Therefore the raw materials have to be looked up, especially in its specifications which are often referred to as indices. Only good indices will lead to a perfect product. This specifications are written down in contracts.
