ByDr Preethi Ramachandran*
1. Compressed Flake Biscuts: Compressed flake biscuits are formed by compression of flakes or cooked grain mixtures with other ingredients. The most used flakes are from wheat that has been precooked with sugar and other flavorings and formed into the biscuit shape. The biscuits can be individually formed, or flakes and other ingredients can be sheeted into a mat and then cut into rectangular forms. The biscuit pieces are then toasted to the desired colour, flavour, and moisture
2. Oven-puffed cereals: These constitute one of the important families of breakfast cereals and include most popular item expanded rice. The kernel expansion is 2 to 5 times than the original volume during oven puffing. Oven puffed cereals have less expansion compared to gun puffed. The preferred rice is medium or short with intermediate amylase content (15-20 %). Waxy or milled rice with high incidences of micro-fissures and fat content (more than 0.25 %) is not recommended because it expands less and yield low quality product. The process is given in Fig. 2.
Fig. 2. process for manufacturing oven puffed rice.
3. Gun-puffed whole grain and milled fractions: The necessary conditions to achieve puffing of grain are prior cooking and application of a strong thermal treatment to increase pressure in a puffing gun programmed to suddenly release the pressure. The expansion rate of the product is affected by moisture content, as the moisture of grain is instantly converted into water vapour when pressure is released (internal and atmospheric pressure equilibrates) and as a result grain expands. The grains used for production of puffed cereal are wheat and rice. The manufacturing process is presented in Fig.3.
Wheat, preferably durum or hard, expanded as whole grain because the pericarp detaches from the grain after the rigorous or harsh expansion. The grain is usually tempered with a saline solution in order to toughen the pericarp and induce the separation of the bran as flakes. The bran is removed by air aspiration and/or screening to yield a puffed decorticated kernel. Regular white or parboiled rice with less than 0.5% fat is also commonly gun-puffed. Rice has excellent expansion characteristics because of its starch properties.
Fig.3. Process used to manufacture gun-puffed cereals.
4. Shredded Wheat: In 1895, Henry Perky was awarded first patent for shredding wheat. Shredded wheat has been a popular breakfast cereal in today’s market. Shredded wheat are produced by both traditional and extruded method. The basic process consists of cleaning, cooking, shredding, pillow formation, baking, flavor addition, cooling and packaging (Fig. 4). Filled shredded wheat biscuits are also available which are usually filled with fruit jams that are placed in between the biscuits.
Fig. 4. Process for manufacturing shredded wheat products
5. Baked Cereals: Baked cereals were one of the first breakfasts item produced and was foremost developed by C W Post at the end of 1800s. These cereals are made from fermented wheat dough and have strong fermented flavor. Whole wheat is mixed with diastatic malt, sugar and other ingredients with limited amount of water so as to prepare firm dough. The dough is allowed to ferment (for 4.5-5 h at 80 % RH and 25-30ºC), panned, proofed and baked. Baking results in dehydrated dense bread and produces the desired flavor, texture and colour. The bread is cooled and ground into granular pieces and re-toasted to remove moisture and enhance flavour. The ground bread is classified, and fines are incorporated into the original formulation. The final granular pieces are commonly mixed with raisins, other dehydrated fruits, and nuts before packaging.
6. Granolas: The popularity of granola is increasing as they are considered nutritious and convenient. The primary raw material used to prepare granola is rolled oats mixed with other breakfast cereal such as puffed rice, wheat, nut pieces, coconut, brown sugar, honey, malt, milk powder, raisins and dates. Sometime soybean products and spices such as nutmeg and cinnamon are also added. The water, oil and syrup are made into a suspension where the dry materials are blended. The resulting mass (wet) is then spread in a uniform layer on a conveyer of a continuous oven dryer and baked at 150-220ºC until mat is uniformly toasted and moisture is reduced to 3 %.
7. Museli Products: Museli products are similar to granola as they are produced from the mixture of several ingredients. The popular ingredient in museli is rolled oats of quick cooking type. The major difference between granolas and muesli products is that granolas are almost always consumed without milk, and muesli is intended to be served with milk and sugar. Museli are also manufactured by mixing one or various types of flakes obtained from maize, rice and wheat and even barley. Sweeteners used are brown sugar and syrups whereas nuts, raisins and dates are added to impart flavor and improve nutritional value.
8. Extruded cereals: Breakfast cereals are typically manufactured using direct expansion or by forming dense pellets. Direct-expanded products are usually flavored and packaged, whereas pellets are usually transformed into their final shape by flaking, oven puffing, or gun puffing.
Extruders for direct expanded products cook, expand, and form the extrudate, which is subsequently sized, dried, or toasted, flavored with liquid or solid mixes, and packaged (Fig 5). Half products and pellet is one of the most popular among breakfast cereals. Many wheat and oat-based breakfast cerealsare manufacturedfrom extruded pellets (Fig. 6).
Fig 5. Manufacture of expanded collets.
The important quality parameters for Ready-to-eat breakfast cereals are bulk, density, texture, colour, sweetness and sensory properties. These parameters are dependent on the characteristic of various types of raw materials and the process involved in manufacturing. For breakfast cereals, the qualities of refined grits and starch are critically important as they affect the organoleptic properties, expansion of product and processing condition. The quality parameters are defined in Table 2.
Fig. 6. Extrusion process to manufacture pellets further processed into gun-puffed cereals.
Table 2. importance of Quality Parameters in RTE Breakfast Cereals.
|
Quality parameters |
Importance |
|
Moisture |
The moisture content of raw materials, tempered-equilibrated blends, extrudates, and finished products affects processing, product quality, and texture of breakfast cereals and snacks. |
|
Water activity |
The determination of the Aw is critically important for low-moisture breakfast cereals snack foods. These products are manufactured to reach certain or given Aw level. Water activity affects microbial growth, enzyme activity and product texture. |
|
Bowl-life test |
The bowl-life test is widely used to test the loss of texture of breakfast cereals after blending with milk. The texturometer equipped with the Ottawa cell and a watertight base is used to perform the test. |
|
Expansion rate or radial expansion |
Test widely used to monitor in plant expansion of extrudates. Many factors affect the expansion rate: quality of raw materials, tempering, extrusion conditions (temperature-pressure gradient), and pressure release valves or vents prior to die forming. |
|
Bulk density |
Bulk density is important because it is closely related to the extrudate expansion rate and extrusion conditions. The advantage of this simple test is that it can be rapidly determined. |
|
Starch content |
This is the most important single component of dry milled fractions, extrudates, and finished products. Starch greatly affects functionality and expansion rate of breakfast cereals and snacks. |
|
Starch gelatinization |
Microscopic technique used to determine the relative amount of gelatinized vs. native starch granules. |
Ready-to-Eat breakfast cereals dominate the market. It constitutes a very diverse range of products and of processing technologies and unit operations. RTE cereals are vehicle for nutrient fortification in many countries where consumption has substantially increased due to more of working housewives. Consumption of these products has significantly increased. While their consumption is fairly stable in developed countries, there is potential for growth in developing countries is much higher. Continuous research in this field will further help in lowering the cost of such products and will help in reaching the lower class in developing countries. This in turn also helps government fortification program to curb malnutrition and related problems.
*Teaching Personnel,
Department of Food Science and Technology
GB Pant University of Agriculture and Technology
Pantnagar
Uttarakhand
