Effect of psyllium husk, basil, and cress seed mucilages on rheological behavior of low-fat chocolate dairy dessert

Nowadays, consumers are more conscious about their diets and pursuit for healthy foods. Healthful diets that are low in fat and rich in fiber may diminish the risk of some types of cancer, particularly colon cancer, a disease connected with many other complaints. Furthermore, such healthful diets are also associated with a reduced risk of type-2 diabetes, a condition that causes a person's blood sugar level to become too high. Continuing problems from high blood sugar may result in heart disease, knocks and diabetic retinopathy which may cause blindness and kidney failure. However, despite a recent trend toward healthy eating behaviors, many consumers still tend to consume unwholesome foods since they make their eating choices just based on food taste. Food texture becomes especially imperative as customers try to find food products containing reduced fat and calories but are not willing to accept inferior eating characteristics. Gums and mucilages are broadly used by food industry to improve food texture and to keep product quality throughout the storage period. Like gums, mucilages are plant hydrocolloids that are similarly formed mainly of galactose, methyl pentose, and pentose sugars linked by glycosidic connections to uronic acid residues. Besides of their gel creating and water holding ability or capacity, mucilages delay gastric emptying. In the present work, the possibility of incorporation of psyllium husk mucilage (PHM), basil seed mucilage (BSM), and cress seed mucilage (CSM) as fat-replacers in the formulation of semi-solid low-fat chocolate dairy desserts was evaluated. The experiments were designed according to a 3-level-3-factor central composite design (CCD) using response surface methodology (RSM). In the formulation of semi-solid low-fat chocolate dairy desserts, three mucilages including PHM, BSM, and CSM (each at the levels of 0-0.2%) were used as the fat-replacers. The responses of interest were the flow behavior (apparent viscosity, consistency index and flow index), rheological properties (storage and loss modulus) and particle size distribution of low-fat chocolate dairy desserts. The results indicated that fat reduction caused significant increase in the flow index of semi-solid low-fat chocolate dairy desserts. All the samples exhibited shear-thinning flow behavior; however, fat reduction significantly (p<0.05) resulted in decreased apparent viscosity, G’, G” and consistency index. In the other word, reduction of fat increased the hardness of low-fat chocolate dairy desserts in terms of rheological parameters fracture stress and Young’s and storage moduli. The fracture stress and Young’s modulus are generally considered as indices of dairy product’s softness, i.e. the higher the uniaxial compression parameters, the firmer the dessert. Storage modulus increased with frequency for all samples reflecting the relaxation of more bonds with more structural rearrangements when the time scale of applied stress was longer. Moreover, storage modulus values were higher than loss modulus values for all the samples over the entire frequency range, indicating the dominant elastic character of the desert samples. Consistency index of all the desert samples were ranged as 3.50-21.82. As expected, as the fat content of desert samples were
reduced, the consistency index was significantly decreased. However, incorporation of mucilages in desert formulation fairly compensate this factor and increased consistency index and resembled it to its full fat dessert. The results of particle size distribution indicated that in the absence of fat (control low-fat dessert), frequency of larger particles increased considerably whereas, incorporating the optimum levels of gums into the formulation of the low-fat dessert shifted the particle size distribution curve to the smaller particle size region. Mucilages are generally normal products of plant metabolism which have several function properties such as mass reduction, nutrient confiscation, as well as a source of protection in contradiction of grazing and ingestion, and heavy metal illumination. This research was performed to investigate the effect of addition of some mucilages as fat replacers on rheological behavior and particle size distribution of low-fat chocolate dessert. Results of present study indicated that addition of tested mucilages could be an effective technique to improve textural properties of semi-solid low-fat chocolate dairy desserts. RSM result demonstrated that using optimum formulations of 0.17% PHM, 0.05% BSM and 0.05% CSM for semi-solid low-fat chocolate dairy desserts would result in reduced-fat products with acceptable rheological and organoleptic properties. Besides being used as a fat replacer and rheology modifier, mucilages could be added as a functional ingredient due to its well-established prebiotic and health promoting effects.