Investigating the gelling properties of chia seed in different model systems and conditions

Chia is a plant known as Salvia hispanica L. and it is Lamiaceae family's member that is grown at arid and semi-arid climates. In the world, the seed production is mainly in Latin America and the Equatorial region. Although it is a plant that grows generally in hot climates such as Bolivia and Paraguay, other countries like Mexico, Australia and Argentina have started to grow chia in the last decade. When the price per ton reached to 8,000$ to 12,000$ in 2013, the demand for production in increased 2014. In recent years, due to their properties such as high dietary fiber content, long-lasting satiety and the valuable unsaturated fatty acids in the chia seeds, they have been regarded as super food and become increasingly popular products. With the demand for healthy and weightloose-aiding products, the market for chia seeds in the world and in our country is growing. Dietary fiber and some unsaturated fatty acids are causing the feeling of satiety by absorbing water at a high amount (27 times of its own weight) and covering the volume in the stomach in the form of a bolus, which aids in loosing weight. Despite positive results in the short term studies, there are not yet enough studies for long term results. As the protein and fat involved in the chia seeds have antioxidant properties, cells are protected against free radicals which can cause some diseases. It also attracts a great deal of attention because it is also effective in neurodegenerative diseases and is a natural antioxidant. It is seen as a promising natural product. In addition, it is supplementing rich mineral content and is recommended for celiac patients due to its gluten free composition. Nutrients content is as follows: 15-24% protein, 26-41% carbohydrate and 25-40% fat. It has been the subject of many studies by its good quality oil content. It possess 55-60% linolenic acid (ω-3), 18-20% linoleic acid (ω-6), 6% monounsaturated ω-9 and 10% saturated fat. Seeds absorb water through their outer layers and form gel on their outer surfaces. Cellulose on the cell wall facilitates the absorption of water. The gel structure obtained is referred to as musilage in many of the studies. In the studies conducted in the literature, the extraction of this structure in general and the structures such as gum and protein obtained from this extract have been studied. From the moment when the chia seeds come in contact with water, gel formation is become immediately. This feature is also suitable for industrial use which will be a quick solution. At the same time, it exhibits a thickening property by forming a gel. It is promising as a stabilizer because it can protect the gel structure for a long time. 50% or more of the emulsifier can be considered as an additive for the civil and chemical industry, besides the food industry. In this study, the aim was to investigate the conditions under which the jelly seeds are formed and how the viscosity of the gels were affected from those conditions. In this content; compositional analysis, and functional properties, of chia seeds were determined besides viscosity tests of chia solutions. Viscosity values in liquids vary depending on temperature, concentration and particle size. This situation has been investigated in liquid mixtures prepared with chia seeds. First, the viscosity of the mixture was measured at 4 different temperature so that the viscosity values could be examined according to the temperature change with distilled water. In the same way, it was also studied at different concentrations to understand the effect of the chia concentration. The effects of pH on gel formation and viscosity, the duration of retention in liquid and finally the effect of the amount of sugar in the mediumon the viscosity were investigated. For the change of the liquid medium, the viscosity values were measured by conducting experiments in milk, having different fat ratios, at different temperatures, gelling times and sugar concentrations. The line spread test (LST), which is an easier method to determine the consistency of the products and easier to apply in everyday diets for dysphagia patients, has also been applied to samples having highest viscosity values. It is an original study as there is no study on the gelation of chia seeds in the milk medium, and at the same time there is no other study examining the change of viscosity in model systems having so many variables. Composition of chia seed; moisture 6.61 ± 0.18%, fat 34.9 ± 1.13, protein 21.49 ± 0.15, ash 4.29 ± 0.04, and carbohydrate 32.71%. Functional properties can be listed as follows; water retention capacity in seed form 43.65 ± 2.959 g water /g sample and 19.20 ± 1.30 g water /g initial, water holding capacity in flour form 19.77 ± 2.31 g water /g sample and 8.7 ± 1.018 g water /g initial, in seed form the oil retention capacity at 10.31 ± 1.20 g oil /g sample and 4.54 ± 0.53 g oil /g initial oil, oil retaining capacity was determined to be 10.10 ± 0.97 g oil /g sample and 4.44 ± 0.42 g oil /g oil. The swelling power for seed and flour were at 25oC 14.05 ± 0.81a g/g, 20.16 ± 2.5c g/g; at 35oC 11,97 ± 0,17a g/g, 20,73 ± 0,58c g/g; at 50oC 10,99 ± 0,59b g/g, 15,69 ± 1,02d g/g; at 70oC 9,9 ± 1,02b g/g, 16,91 ± 0,44d g/g. It was seen that the increase in temperature decreased the swelling power. The emulsifying ability of the seeds was determined as 50% and the stability was 53.66 ± 1.63%. Fort he freeze-thaw stability of whole seeds. In the first freezing and thawing period, the amount of water that was separated was 33.33%, while the amount of water that was separated during the second period increased to 46.66%. This showed that some of the water in the chia seeds that have been frozen and thawed and then frozen, was lost. In the gelling investigations, it was found that the amount of gel formed in the acidic pH levels was the lowest and highest viscosity level was in the milk medium, for the light milk (containing 1.3% fat). At the same time, it was observed that the chia seed flour formed gel by drawing more water in all media, but this structure was weaker than gel in the whole sample. It was determined by DSC that the gelling started in the range of 20-35oC and the maximum gelling was in the range of 30-44oC, but the temperature at which the gel structure deterioration started was between 77-82oC. In the viscosity measurements, the maximum point was detected at 12,59 ± 1,09a cP at 24°C 24 h for whole milk, 10% sugar and 2% chia seeds model system. In the water model, the samples were prepared at 25°C also had high viscosity values. However, conditions such as acidic environment and high temperatures were identified as factors reducing the viscosity. It has been shown in our work that the seeds can be used as nutrient additives in the food industry in terms of both their nutritional content and their functional properties. With the ability to form gels, they can be used directly in many cases to increase the consistency. As the future study; it is suggested to make studies in both model systems and product applications by considering oth