MC, HPC, and gellan gum has been proven to fat absorption into pastry mix by 50 to 91 percent, but MC was found to reduce fat uptake more than other films. Also, MC and HPMC, corn zein and amylose were used to coat Akara, a West African food made from whipped cowpea paste. The effectiveness of the two methods (spraying and dipping) of application were evaluated as well; all three materials significantly reduced fat uptake in deep fried Akara in both application methods. MC coating applied by dipping was the most effective (49 percent) among all three materials. However, deep fried Akara coated with MC and HPMC had a shiny, smooth, and glazy appearance, contrary to the uncoated and products coated with corn zein and amylose.
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Alginate. Alginate is another type of polysaccharide that has been used as lipid barrier in deep-fat frying. It can form coatings with or without gelation through solvent, electrolyte cross-linking (calcium) or injection of a water-miscible non-solvent for alginate.
Proteins are broad range of macromolecules that are found in both animals and plant sources. Protein-based coatings have been explored as potential coating materials in fat-uptake reduction. Plant sources of protein-based coatings include corn, wheat, and soy whereas animal sources include milk, whey, and muscle protein. Proteins are made up of 20 smaller units called amino acids which are attached to one another in long chains. However, polysaccharides such as starch and cellulose are consisted of glucose units that joined together. This imposes increased functional properties on the protein, mostly making it potent for intermolecular bonding. The amino acid consists of an amino group (-+NH3), a carboxyl (-COOH) group and a residue, R group, that is attached to a central carbon atom. The R group, also known as side chain, determines properties such as polarity, solubility, acidity, etc., of the amino acid. The arrangement of the amino acid determines the structure and name of the resulting protein. Peptide bond join several amino acids to form protein. Protein gelling is influenced by both intrinsic and extrinsic factors. Gelling occurs primarily due to an increased limited protein-protein interactions as well as a decrease in the protein-water interactions and these are influenced by external factors such as heat, pH, or ionic strength. Gelling is intrinsically influenced by protein concentration, composition, and extent of denaturation of the protein. Proteins have a three-dimensional conformational structure, and this tends to form networks during unfolding (denaturation). The loss of this native 3-D structure of protein by heat, acid, base, and/or solvent is necessary in order to form the more extended structures that are required to from film. Comparatively, proteins are able to form films with better mechanical and barrier properties than polysaccharides. However, films made from proteins are prone to cracking because of strong cohesive energy of the polymer.
The selection and use of protein materials in edible coating faces a major challenge as to its general acceptability. A number of people are allergic to certain proteins, as their Generally Recognized As Safe (GRAS) status must be a characteristic feature as well. Generally, unlike animal-based proteins, plant-based proteins are associated with the allergenic reactions, placing a limit on their broad application.
A 2009 issue of Journal of Food Engineering investigated the influence of the use of edible coatings from whey protein and soy protein isolate during deep frying of a pre-fried, frozen product performed from cassava. Authors showed that whey protein had the best results with fat absorption, presenting a reduction of 27 percent for the cassava puree product.
A 1997 issue of LWT – Food Science and Technology indicated almost 60 percent reduction in fat uptake on potato cuts coated with corn zein. They form films that are brittle, and therefore require plasticizers to increase their flexibility.