Evaluation of Protein Quality, Phytochemical Characterization and the Effect of Soaking and Roasting Processes on Raw Apricot Kernels

Abstract
 
The aim of the study was to assess the protein quality of raw apricot kernels and study the effect of soaking and roasting processes on the bioavailability of the treated samples. Raw apricot (prunus armeniaca) kernels were subjected to roasting, soaking and soaking followed by roasting processes. Chemical composition, mineral content, phytochemical characterization, amino and fatty acids analysis of treated kernels meals were performed. Protein quality (biological value, digestibility and net protein utilization) was conducted using male albino rats.
 
The quality of the extracted oils was judged by measuring peroxide value, free fatty acids and iodine value. GC-MS analysis of treated kernels meals and extracted oils was included in the study.Biological value of raw apricot kernels (RAK), roasted kernel (RK), soaked kernels (SK) and roasted soaked kernels (RSK) meals were of 79.34, 49.14, 72.94 and 64.66%, respectively. True digestibility ranged from 94.0, 77.14, 93.65 and 85.33%, respectively. Net protein utilization recorded 74.58, 37.91, 68.31 and 55.17, respectively.The results indicated that crude protein was 31.45, 37.15, 27.1 and 26.7%, respectively.
 
The tested samples had high fat content valued 31.07, 17.25, 35.05 and 38.91%, respectively. Fibers ranked for 11.4, 15.6, 17.51 and 19.04%, respectively.Carbohydrate amounted to 17.3, 21.9, 13.94 and 9.73%, respectively. Raw and roasted kernels had maximum phosphorous content of 6109 and 6963 ppm, followed by soaked kernels (2645) and roasted soaked kernels (2327). All samples were packed with iron (48.55-60.15 ppm), zinc (33.49-54.30 ppm) and copper (9.46-15.8 ppm). Amino acids profile ascertained that glutamic was the most abundant recording 6.51, 6.66, 6.08 and 5.77%, respectively. Total antioxidant capacity of the roasted kernels was 2301, followed by raw kernels (1127), soaked kernels (190) and finally roasted soaked kernels 311.3 mg AAE/100g. Ferric reducing antioxidant power (FRAP) increased by increasing the concentration mediating a high reducing ability of all type of kernels.
 
Total phenols accounted for 13.68, 26.48, 17.06 and 18.64 mg GAE/100g, respectively and flavonoid content were 6.12, 10.52, 5.67 and 8.14 mg QE/100g, respectively. Qualitative determination of glycosides ensured its presence in the raw and treated kernels. Soaked kernels had the low concentration of tannin (0.57%) considered as anti-nutrient factor.GC-MS analysis of RAK and RK revealed the existence of amygdalin at 2.47and 0.83%, respectively. Whereas, SK and RSK were free from amygdalin.  The extracted oils had peroxide value of 23.17, 5.79, 1.67 and 2.34 Meq o₂ /Kg oil, respectively. Free fatty acid valued 2.66, 0.12, 7.3 and 6.58%, respectively. Iodine value registered 106.13, 106.5, 106.43 and 105.19 mg KOH/g, respectively. Fatty acid profile ensured that oleic acid was the most abundant in all tested oil samples accounted for 60.82, 60.54, 60.54 and 61.49%, respectively. Linoleic acid was the second major fatty acid valued 25.94, 26.06, 26.07 and 26.13%, respectively. GC-MS analysis ensured the presence of several structural related bioactive compounds in the extracted oils. It can be concluded that raw and treated apricot kernels are good sources of protein, fat and fiber and considered as natural antioxidants packed with iron, zinc, phosphorous and copper. Thus, kernels served as potential sources for use in several food industries