Have you ever wondered how beer is made and why different varieties of barley are perceived differently by brewers?
This article provides a brief description of the process of producing barley malt (maceration, malting, and drying) and the three main quality characteristics of barley malt (malt extract, mashing capacity, and wort viscosity).
Barley was one of the first grains used for human consumption, with its use in brewing dating back to at least 3000 BC.
Barley possesses several grain properties that make it more suitable for malting and brewing compared to wheat.
Barley husks protect developing shoots during germination, embryos during processing, and serve as a filter aid during brewing. Sprouted barley has a firmer internal consistency than wheat, allowing for easier handling during germination.
Malt serves as the precursor to brewing grains. It removes the inner cell wall barrier, stimulates the production of saccharification enzymes (which convert starch into malt extract), and enhances flavor and color development.
All malted barley varieties exhibit differences in malt quality. They vary in their soaking profile, germination rate, and optimum germination temperature, necessitating the germination of only one variety at a time.
The malting process consists of three key steps:
Steeping initiates the germination process by increasing the grain moisture from 10% to 42-48%. This involves immersing the grain in aerated water for five to eight hours, alternating with periods of air rest (draining the water from the grain).
The grain is then transferred from steeping tanks to germination boxes for root and shoot production. The endosperm, which serves as the energy source during initial growth, undergoes structural changes known as modification.
The production of diastatic enzymes in the grain is controlled by manipulating humidity and germination bed temperature.
The goal of germination is to maximize grain modification while minimizing root and shoot growth, as excessive growth leads to reduced malt extract.
Germination is halted by kilning when the barley shoot reaches about three-quarters the length of the grain (approximately four days). Kilning involves drying the grain and promoting flavor and color development.
Low temperatures are employed to ensure the survival of diastatic enzymes required for subsequent brewing processes. This is followed by a gradual temperature increase to achieve desired flavor and color changes. Malt kilned at higher temperatures produces darker-colored beers.
ACE 1000L brewery equipment
Malt quality parameters
There are two quality specifications for malting barley: grain quality parameters used by maltsters in purchasing grain, and malt quality parameters used by brewers.
The three most important malt quality parameters are:
1. Malt extract
2. Diastatic power
3. Wort viscosity
Malt extract measures the amount of fermentable sugars, determining the alcohol yield per tonne of grain. Higher extract levels result in greater alcohol production.
Malt extract is measured by malting the grain and measuring the soluble sugar content (e.g., glucose and maltose) in a mixture of hot water and ground malt (known as wort). The measure is presented as a percentage (dry basis).
The export standard for malt requires a minimum malt extract level of 80%, typically achieved with a four-day malt.
If maltsters use low-quality grain, they cannot meet this minimum target. Therefore, they must meet the specifications set by the brewer to ensure the purchase of the malt.
High protein content and small grain size contribute to increased production costs, decreased yield, and reduced efficiency.
Diastatic power measures the quantity of diastatic enzymes (such as α-amylase, β-amylase, and limit-dextrinase) present. These enzymes convert the starch in the grain into soluble sugars or malt extract. The levels of these enzymes are crucial for achieving the desired malt extract quality.
Diastatic power is measured by assessing the enzymic activity in the malt and presented in units of Windisch-Kolbach (WK).
The level of diastatic enzymes is directly related to the protein concentration in the grain since these enzymes are proteins themselves.
Wort viscosity measures the stickiness of wort relative to water, which reflects the stress experienced by the plant during grain filling. Genotype also plays a significant role in wort viscosity.
Wort viscosity is determined by measuring the amount of β-glucan (a type of cell wall material) in the wort, presented in units of centipoises (cP).
Barley grains with low viscosity germinate evenly, whereas high cell wall material can impede the conversion of starch into malt extract. Highly viscous malt retards the separation of sugar-rich wort from the husks during brewing, slowing down daily beer production and increasing costs.
Genotypes vary in malt quality
Malt quality is influenced by both environmental and genotypic factors. Genotype plays a crucial role in determining the potential quality of a barley variety for malt and beer production, which can be achieved through effective management.