May 01, 1997
by Teresa Acklin
Industry consultant David Sugden explains how millers can add value by processing and marketing flour byproducts.
Flour byproducts, called coproducts in some countries, comprise a number of categories. In many markets, some of these byproducts command a premium over millfeed, even over flour itself.
Three specific wheat flour byproducts wheat germ, common wheat semolina and bran, which includes millfeed can offer nutritional and other advantages over competing cereal grains, depending on end uses and markets. The table on this page illustrates the differences in composition among wheat and byprod-ucts and other whole cereals.
Both oats and maize have a high oil or fat content, but less than wheat germ. Maize has low mineral content, whereas rice has a high content. Both rice and oats have high crude fiber percentages, with wheat the third highest. Oats have the lowest carbohydrate content among whole grains. Wheat flour at 75% extraction shows a drop in protein, fat, crude fiber and mineral content compared with whole wheat.Wheat Germ Processing and Uses
Wheat germ, which contains 25% or more protein and around 10% fat or oil, more often than not commands a premium that is often close to the value of flour. The germ yield from top class North American high protein hard wheats will be up to 0.75%. Because of their nature, soft European wheats will deliver germ yields of somewhere between a half to two-thirds that of hard wheat.
A common way to extract wheat germ is to rely on the first tailings roll passage (F roll), which is smooth, allowing the following sifter top sieves to separate the wanted germ. The sieve numbers could be as fine as a 28 wire, or about 700 to 720 microns, although slightly coarser sieves are probably preferable for purity's sake.
Another method is to prebreak wheat on an Entoleter or similar equipment to loosen or knock out the germ. A sifter follows this process, with the wheat going to first break and the finer fraction to a pair of smooth rolls. The rolls feed another sifter for maximum germ extraction.
Raw wheat germ has a relatively short life before rancidity sets in, and hot and humid climates shorten this period to only a few days. Accordingly, it is paramount to ensure delivery to the customer speedily.
The client may well either toast, roast or steam the wheat germ, depending on his market, with the decision based on desired final organoleptic characteristics. All three processes stop rancidity and allow an extended shelf life. Moreover, germ cooking by any method tends to prevent glutathione, a natural substance present in germ, from destroying the loaf volume of germ enriched bread.
Cooked or processed germ is used in bread, cookies and baby foods or is sold separately to pharmacies or health food shops because wheat germ is a significant provider of vitamin E. Extracting oil from the wheat germ is another possible use, although maize usually is a more competitive oil source.
Another reason germ may be extracted is to ensure minimal oil contamination of white flours. In long extraction white flours where germ oil is present, bread volume suffers.Semolina and Bran
Semolina from common wheat has a number of uses, although it will not make pasta products of the same cooking, appearance or eating quality as durum. Semolina from common wheat can be bled off simultaneously with flour from the mill, and a typical offtake is between 1% and 5% of wheat.
Semolina's value is the same as top patent flour at best, and so it is a premium product. Its analysis is similar to top patent flour, with low ash and low fiber contents.
The difference, of course, is one of particle size, with semolina being around 250 to 400 microns. It usually is taken from the first and second break fine middlings purifier (fine semolina).
Uses include semolina puddings, lower grade pasta, retail packs and dusting flour for bakeries. In its finest and purest (low speck) forms, it is also used as a home-baking free-flowing family flour for bread.
Bran, which in this context means not just bran but straight grade millfeed, contains significantly higher percentages of protein, fat, crude fiber and mineral content than wheat, as seen in the table. Note also bran's smaller percentage of carbohydrate.
Bran's varied and relatively high vitamin content compared with 75% extraction white flour is nutritionally beneficial, and the fiber source is used effectively in both human and animal foods. Products for human consumption include bread, cookies and breakfast cereals, especially coarse bran.
A premium market over millfeed can be found for coarse bran, preferably the coarser the better, for horses. Bran for this market would he sieved over an 8-wire or 2,750-micron aperture.
Loose bran and millfeed are produced in time honored fashion from the break and reduction systems continuously, and they can be stored and delivered in bulk or bags. These days, precautions are taken in many markets to ensure all millfeed is passed over a magnet and even a metal detector for product purity, a practice that formerly was uncommon.
Pelleting of millfeed and bran also is increasing in some quarters. The process is simple, consisting of using a pellet mill with steam or cold water plus a cooler and sieve for fines extraction.
Pelleting has a number of advantages and disadvantages. Advantages include compressibility, from a unit volume of 350 to 400 kilograms per cubic meter to 650 to 700 kg. Compression makes the pellet almost as heavy as wheat at 750 to 800 kg per cubic meter; this feature enables pellet storage in elevators, whereas loose bran and millfeed cannot be stored in elevators.
Pellet sizes can range from 6 millimeters to 12 mm in diameter and about 2 to 3 times that in length. Generally, the bigger the pellet the greater the capacity throughput, although the 12 mm diameter pellet is almost too big for many customers.
Pellets can be made with either steam or water at ambient temperature. The penalty for using water is a drop in capacity of about 30%.
Transportation is the big advantage of pellets compared with loose material, especially if it is organized and paid for by the miller. Some customers will pay a premium at the compounders gate, and in some cold, dry climates and countries it also is possible to make a legal weight gain.
Disadvantages include the capital and operating costs of pelletization. Further, pelletization works only if a market exists, which assumes the compounder can grind the product.
Maintenance and supervision are further difficulties. All climates demand proper and even cooling of pellets to equilibrium. If not, bacteriological problems or worse occur.
Analytically, there is no difference between loose or pelleted material. However, when steam is used, a certain cooking of the remaining starch does take place, providing greater digestibility for the animal.
David Sugden, independent consultant to the grain industries, may be reached at The Coach House, Killigrews, Margaretting, Ingateston. Essex CM4 0EZ, U.K. Tel: 44-1245-352048. Fax: 44-1245-251162.Cereals composition
| in percent|
|*Source: Modern Cereal Chemistry, Kent-Jones and Amos.|