| Seinat (Cucumis melo var. tibish) seeds are a source of protein and edible oil having various uses. Keeping in view the potential of seinat as an under-explored oilseed, this research was conducted to investigate the physiochemical characteristics, evaluate the nutritional properties, assess the functional properties, and study the antioxidant activity by different methods and finally apply in some food products such as wheat flour bread, butter and edible oil.In the first, proximate composition, minerals, amino acids and fatty acids of the dry fruit, pulp, and seed from seinat were studied. The weights of dry fruit, seeds, and bulbs were 6.19, 2.16, and 4.03 g, respectively, and the percentage of seeds was 34.89% for dry seinat fruit while the length, diameter and thickness of seeds were 5.95,3.80 and 2.25 mm, respectively. Crude oil content of seinat seed flour was 31.1%, while the moisture, fiber, proteins, ash and total sugars content was 4.2%,24.7%,28.5%,4.3%, and 6.9%, respectively. The contents of potassium, the highest mineral in seinat seed flour was 9,548.33 mg/100 g. Seinat seeds contains the essential amino acids, with isoleucine, threonine, lysine, histidine, methionine and tryptophan.Secondly, seinat seeds were analyzed for their chemical composition of the oil in addition to antioxidant activity. The main fatty acids were linoleic, oleic, palmitic, and stearic acids (61.10%,18.75%,10.37%and 9.18%, respectively). The total phenolic content was 28.17 mg/g oil. Seinat seed oil also contained a good level of tocopherols; of which δ-tocopherol (63.43%) showed the highest content. β-sitosterol was found at 289 mg/100g oil of total sterols (302 mg/100g) in the oil. Seinat oil showed a good antioxidant activity in four assays including reducing power, β-carotene bleaching inhibition activity, ABTS and DPPH radical scavenging activities.The next phase, the physicochemical and functional properties of seinat seed flour (SSF), defatted seinat flour (DSSF), and protein isolates were studied. Protein was extracted from DSSF using an alkali solution with isoelectric precipitation and freeze-drying. Freeze dried seinat seed protein isolates (FSSPI), SSF, and DSSF were evaluated for their physicochemical and functional properties. FSSPI contained 91.83% protein versus 28.58% for SSF. The amounts of potassium, the mineral with the highest content, were 9,548.33,6,439.03, and 1,029 mg/100 g in SSF, DSSF, and FSSPI, respectively. The protein solubility of FSSPI was significantly higher (p<0.05) than for DSSF and SSF. FSSPI has a significantly better (p<0.05) foaming capacity, water/fat absorption capacity, and bulk density than SSF and DSSF.The effect of enzymatic hydrolysis on nutritional parameters, functional properties and antioxidant activities of seinat seed protein isolates were studied. Hydrolysates of seinat seed protein isolates (HSSPIs) were prepared at different time intervals (30-180 min), by using two food-grade proteases; firstly, trypsin and then pepsin. Hydrolysis time showed significant differences (p<0.05) in nutritional parameters. All the functional properties studied decreased as hydrolysis time increased. Antioxidant activity; DPPH and ABTS radical scavenging assays and ferrous chelating activity of HSSPIs increased with increase in hydrolysis time. Large amounts of small-sized peptides (3,000 - 5,000 Da) were also investigated decreased as hydrolysis time increased (2.07 - 1.28%). The results in this study indicate that increase in hydrolysis time positively affects nutritional and antioxidant properties of HSSPIs, while the functional properties that were studied are negatively affected with this increase. On the other hand, In vitro antioxidant activity of glutelin, albumin, and globulin seinat seed protein hydrolysate (SSPH) fractions was also assessed. The SSPH fractions were prepared using two food-grade proteases; trypsin and pepsin. The total amino acid composition, molecular weight distribution, and total phenolic contents were evaluated. The antioxidant activity, hydroxyl and DPPH radical scavenging activities, metal chelating activity, and reducing power were also tested. The protein content of the glutelin, albumin, and globulin SSPH fractions was 81.80%,73.09%, and 50.95%, respectively. The SSPH fractions showed high reducing power. Their molecular weights were in the range of 300 to 5000 Da. The glutelin fraction hydrolysate showed the highest content of the total phenolic (43.53 μg/mL GAE) and the strongest antioxidant activity. The inhibitory concentration of 50% (IC50) of DPPH and hydroxyl radical scavenging assays and metal chelating was lower (p<0.05) in the glutelin compared with that in albumin and globulin fractions. The results indicated that hydrolysates derived from seinat seed protein can be considered to be antioxidant sources.Seinat seeds protein concentrate (SSPC) and seinat seeds protein isolates (SSPI) were added to wheat flour (WF) to make bread. The effect of supplementing wheat flour with 5, 10, and 15% seinat seed proteins on physicochemical, nutritional and sensory properties of bread was evaluated. Dough characteristics were studied using a Brabender Farinograph and Extensograph. Loaves were prepared by using the straight dough procedure. Water absorption was increased (p<0.05) as the protein level in the blends increased. The dough stability time decreased (p<0.05) with addition of SSPC and SSPI. Addition of 15% SSPC and SSPI to WF did not have any effect on loaf sensory characteristics. WF protein content significantly increased on addition of SSPC and SSPI. The study demonstrated that addition of SSPC and SSPI increases essential amino acids, mineral, biological value and chemical score, thus improving the nutritional value of bread.In the last part, seinat kernel butter was made and mixed with peanut butter. As regard to the minerals, the results showed that seinat seeds butter was rich in Na (420 mg/100g), Ca (6.90 mg/100g) and Fe (35.50 mg/100g). In addition to that, its protein digestibility was high and reached 77% and 83% for seinat butter and mixed butter, respectively. The panelist results showed that seinat kernel and mixed butter had no significant differences in overall acceptability. Also, seinat seed oil was blended with peanut oil for the enhancement of its stability and chemical characteristics. The physicochemical properties (relative density, refractive index, free fatty acids, saponification value, iodine value and peroxide value) of seinat seed oil and peanut oil blends; 95:5,85:15,30:70 and 50:50 proportions were evaluated, as well as oxidative stability index, differential scanning calorimetric characteristic and tocopherols content. According to the results in chemical composition of oil blends, there was no negative effect by the addition of seinat seed oil. Addition of seinat seed oil to peanut oil had increased the stability, tocopherols content and polyunsaturated fatty acids.This study is the first investigation on seinat seed, which was grown in Sudan opening the way for further studies about these seeds. The results showed that seinat seeds are a rich source of important nutrients such as the protein, edible oilseed and antioxidants that appear to have a positive effect on human health. The present study provides a base for exploring the seinat seed and their application in foods. |
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