Production of functional gluten free biscuits by using CHIA (Salvia hispanica) seeds and determination of quality characteristics

In this study, it was aimed to produce sweet and salted gluten-free biscuits by using chia seeds in different proportions as a substitute of processed red rice flour and tapioca corn starch mixture. Chia seeds were used in biscuit production by replacing processed red rice flour and tapioca starch at four different ratios (0, 10, 15 and 20%). Physical properties (diameter, weight, thickness, spread factor and spread ratio), chemical properties (moisture, ash, total dietary fiber, crude fat, crude protein and carbohydrate), functional analysis (antioxidant activities, total phenolic content) before and after in vitro digestion, color (L*, a* ve b*), texture (hardness), sensorial properties (appearance, falvour, taste, odour, texture, overall acceptability) of gluten free biscuits were investigated. These gluten-free biscuits were compared with the control biscuits which were produced with 100% processed red rice flour. In addition some physical and chemical analyses were performed at the end of the storage periods of 2, 4 and 6 months and the effect of storage on these properties were investigated. As amount of chia seeds increased, the weight, diameter and thickness ratios increased in sweet and salted gluten-free biscuits. Besides, in sweet biscuits an increase in L* values from 58.16 to 46.72 and in b* values from 27.20 to 22.55 was observed due to concentration increase, whereas there was no significant difference in a* values. When the chemical properties were examined; as the chia seed ratio increased; moisture, ash, protein, fat and total dietary fiber contents of sweet and salted biscuits also increased but carbohydrate content decreased. When the functional properties of the biscuits were examined, as amount the chia seeds increase, resulted in an increase in total phenolic content (0.71-1.24 mg GAE/100g for sweet biscuits; 0.61-0.83 mg GAE/100g for salted biscuits), FRAP (10.22-17.74 µmol Fe(II)/g KM for sweet biscuits; 9.23-13.60 µmol Fe(II)/g KM for salted biscuits) and DPPH radical scanvenging activity (2.58-3.74 µmol trolox/g KM for sweet biscuits; 2.22-3.68 µmol trolox/g KM for salted biscuits) results. Additionally, according to the in vitro digestion results of gluten-free sweet and salted chia-substituted biscuits, the total phenolic and antioxidant activity values of the products increased as the chia ratio increased. As a result, substitution of chia seed with red rice flour resulted in sensorially acceptable and functional gluten free biscuits with high nutritional quality. Free fatty acid and peroxide values of biscuits increased till 4th month and decreased at the 6th month of storage. Accordingly, a decrease in pH values of biscuits till 4th month and an increase at the 6th month was observed. Peroxide values of sweet biscuits ranged between 5.75-14.61 meq O2/kg where peroxide values of salted biscuits ranged between 3.05-16.38 meq O2/kg. Free fatty acid ratios were detected between 0.91-2.74% oleic acid in sweet biscuits and between 0.96-1.98% oleic acid in salted biscuits. According to sensorial analysis results; the overall acceptability decreased as a result of increasing chia ratio and storage period. 10% chia substituted salted biscuits had the highest (6.12 point) overall acceptability score and was not different from control biscuit statistically. Key Words: Chia seed, gluten-free biscuit, functional biscuit, celiac disease