This study aimed to improve the steaming process of black sesame seeds. A comprehensive evaluation was conducted using the grey-correlation method based on the variation-coefficient weight to observe the treatments of normal-pressure (NPS) and high-pressure (HPS) steaming (with/without soaking in water) for nine cycles. Their effects on the contents of water, protein, fat, ash, melanin, sesamin, and sesamolin of black sesame seeds, as well as the sensory score of the black sesame pill, were determined. We found that with varied steaming methods and increased steaming cycles, the contents of the nutritional and functional components of black sesame seeds and the sensory score of the black sesame pill differed. The results of the variation-coefficient method showed that water, protein, fat, ash, melanin, sesamin, sesamolin, and sensory score had different effects on the quality of black sesame seeds with weighting factors of 34.4%, 5.3%, 12.5%, 11.3%, 13.9%, 11.3%, 7.8%, and 3.5%, respectively. The results of two-factor analysis of variance without repeated observations indicated that the grey-correlation degree of HPS was the largest among the different steaming treatments, and the following sequence was HPS after soaking in water (SNPS), NPS, and SNPS. There was no significant difference between NPS and SNPS (p < 0.05). Moreover, with increased cycles, the value of the grey-correlation degree increased. The comprehensive score of the procedure repeated nine times was significantly higher than other cycles (p < 0.05). The results of the grey-correlation degree and grade analysis showed that the best steaming process of black sesame seeds was HPS for nine cycles, followed by HPS for eight cycles and NPS after soaking in water (SNPS) for nine cycles. These findings could provide a scientific basis for replacing SNPS with HPS to simplify steaming and realize the parametric steaming of black sesame seeds, and thus, ensure the quality of black-sesame products.
Keywords: black sesame; grey-correlation degree; high-pressure steaming; nine steaming nine drying; variation-coefficient method.