Effect of oat flour and pumpkin powder on nutritional value, staling and organoleptic properties of chocolate cake

Regarding the problem of celiac patient's intestinal intolerance to gluten-containing products, these people have to use gluten-free products, mostly with a variety of foreign and high prices ingredients that are not conform to Iranian tastes. The aim of this study was to evaluate the possibility of producing gluten-free chocolate cake with Acorn flour (30 and 40 percent) and powdered squash (5, 10 and 15 percent) Along with rice flour (100% Control sample, 45, 50, 55, 60, 65 percent with Acorn flour and pumpkin powder. Acorn flour may be used in gluten-free flour breads due to its nutritional and health benefits. Acorn flour contains high quality proteins with essential amino acids (4–7%), relatively high amount of sugar (20–32%),  starch (50–60%), dietary fiber (4–10%), and low amount of fat (2‒4%).  It also contains vitamins E, and B, potassium, phosphorous, and magnesium. Pumpkins. are extensively grown in tropical and subtropical countries. They are traditionally consumed as freshly boiled and steamed or as processed food items such as soup and curry. Pumpkin is high in carotene, which gives it yellow or orange color. It is also high in carbohydrates and minerals. Beta-carotene in plants that have a pleasant yellow-orange color is a major source of vitamin A.

In this study, the effect of Acorn flour and pumpkin powder on the nutritional properties of cakes (fiber, beta-carotene), moisture, water activity, stale, special volume, stiffness and sensory properties were tested. Increasing levels of employing Acorn flour and pumpkin powder in the formulation gluten-free chocolate cake directly increases water activity, including dietary fiber and beta-carotene content in chocolate cakes. It was also found that by increasing the percentage Acorn flour and pumpkin powder in the formulation gluten-free chocolate cake staling rate was decreased. Based on the results from sensory evaluation by trained evaluators, all sensory characteristics (texture, taste, smell and appearance) was significantly (p <0.05) affected by different levels of Acorn flour and pumpkin powder. 

Addition of pumpkin powder resulted in considerable increase of batter viscosity while the addition of Acorn flour had no significant effect on viscosity (p> 0.05). The higher viscosity was expected to have higher resistance to the applied shear during the mixing process leading to a lower amount of air being incorporated. Peak viscosity increased with increasing Acorn flour content. Acorn flour and pumpkin powder substitution, increased the fiber content of flours and increase the absorptive and maintenance capacity of water, as well as the dough viscosity of gluten-free chocolate cake. Addition of 30% Acorn flour and 10%pumpkin powder was found to increased batter viscosity, apparent density, cake moisture. The specific volume of cakes were decreased due to the inverse relationship between volume and apparent density. The effects of Acorn flour and pumpkin powder as a staling retarder was further due to increase in fiber content which results in moisture retention of cakes. Hardness of all samples including control, were significantly increased during storage (p <0.05) which is indicative of staling during the storage period. The maximum firmness of samples was achieved in control and the minimum was seen in samples with high levels of Acorn flour and pumpkin powder. Substitution of Acorn flour and pumpkin powder into cakes, seems to reduce the rate of firming during storage. Acorn flour and pumpkin powder showed an anti- staling effect, retarding the cake firmness during storage.  The main reason of staling in gluten free products is moisture migration from crumb to the crust which is due to the absence of gluten. Fibers are expected to increase water retention and loaf volume and to decrease firmness and starch retrogradation. The highly hydrophilic nature of fibers also helps to prevent the migration of water from the substrate to the coating, which improves shelf life of the product. According to the surveys and assessments carried out, in term of physico-chemical, treatments sensory of T2 (with 30% Acorn flour, and 10% pumpkin powder. And 60% Rice Flour) were proposed as a selected treatment.