It is controlled germination process that activates enzyme of resting grain resulting in the conversion of cereal starch to fermentable sugar and partial hydrolysis of protein and other macromolecule. During malting, large molecular weight components of endosperm cell walls, the storage protein and starch granules are hydrolyzed by enzymes rendering them more soluble in water. All cereals grains are capable of undergoing malting barley is the best. Barley is best for malting because, the husk tightly protect the endosperm and developing germ. Also husk aids as filtration aids dring brewing and making extraction easy. The most suitable type of barley for malting are
- a) Two row barley ( Hordium distichum): They have low enzyme content, more starch and less protein. They have thinner husk than six row barley. They also have higher starch content which is principle contributor to extract.
- b) Six row barley (Hordeum hexastichum): They have high enzyme content for converting starch to fermentable sugar. They have more protein and thicker husk in comparison to two row barley. The higher level of enzymes makes six row barley desirable for conversion of adjuncts starches.
Characteristics of good malting barley:
- No or low bacteriological load
- High germination capacity (greater than 94% and having adequate enzyme activity. Loss of enzyme activity can result from embryo damage during threshing or overheating during drying or storage.
- On mashing, should produce maximum amount of extract
- Should have low content of husk (less than 11%)
- Grain should have high starch content and low protein content. High protein (N2) barley is not suitable for brewing because as nitrogen content increases, starch content decreases and yield of malt extract is directly proportional to starch content. It is starch which is converted to maltose and dextrin and are important fermentable constituents.
- High nitrogen barley requires long time for modification (conversion of starch and protein into simpler substances) and thus more malting time is required, resulting more root elongation and greater respiratory and metabolic loss.
- The malt from high nitrogen barley contains relatively high soluble protein or albuminoidal materials which form haze and lowers the keeping quality of beer. Furthermore, development of haze will make favorable condition for microorganism growth.
- Barley: Sound and freshly harvested barley of moisture content 15% is used.
- Kiln Drying: done for moisture reduction to 10 – 14 %.
- Cleaning: barley cleaning is done by screening removing dust, chaffs, corn and weed seeds.
- Aging: normally done for about 3 weeks. The secondary ripening process occurs during aging, so that grain will be ready to germinate.
- Grading: in malting, enzyme activation during germination is different for different size barley. Hence grain uniformity is very important in malting process. It is done by barley grader.
- Steeping/ soaking: it is done at 10 -12°C for 40 to 60 hours. Moisture content at the end should be 40 – 50 %. The time for steeping depends upon plumpness. High temperature soaking is associated with enzyme destruction. The main function of steeping is to provide a condition in which natural germination can proceed until the optimum enzyme activity has been developed. About 0.5 to 1.5% of dry matter is lost in the steeping process.
- Germination: For this purpose, grain is removed from the soaked water and allowed to germinate. It takes 3 – 4 days for germination. Moist air is forced through the germination bed. Temperature is maintained at about 12° The process is completed when plumule is 1/3rd to 2/3rd of the length of the kernel. Enzymes are liberated during this process. The enzymes to be activated is “cytase” which hydrolyses cell wall. This helps to liberate starch content in the endosperm cell. Another enzyme “Amylase” become active t later stage.
- Kilning/ drying: controlled drying process is carried out and grain is dried up to 13% moisture content. Germinated grain develops flavor is developed during this process. Drying process helps to terminate the growth and stops physiological and biochemical process.
- Milling: milling of germinated dried barley is very similar to wheat milling. Both dry milling and wet milling can be carried out.
- Storage: freshly milled barley malt is packaged and stored at cool and dry condition for future use.