สมบัติทางเคมีกายภาพของสตาร์ชที่แยกได้จากเนื้อในเมล็ดมะม่วงของมะม่วง (Mangifera indica L.) พันธุ์ที่ปลูกเป็นหลักในประเทศไทย

Abstract

In Thailand, mango seeds are disposed from mango processing plants at least 1 metric ton per week and mango seed kernel (MSK) still contain large amount of nutrients, especially starch. However, MSK has not been extensively used. This might be due to the limit of basic information. Therefore, this study aims to investigate and compare chemical compositions of MSK from three mango cultivars (Namdokmai, Kaew, and Chokanun) primary cultivated in Thailand. Furthermore, the physicochemical properties of starch from MSK were also studied and compared with those of other starches mainly used in the industry (corn starch, tapioca starch, rice starch from Hom Mali and Chiang Phatthalung cultivars). From the chemical compositions analysis, carbohydrate was the major component found in MSK. The investigation in starch chemical properties revealed that MSK starches contained lipid and amylose higher than other starches. The weight average molecular weight (Mw) of amylose and amylopectin of MSK starches were smaller than those of other starches. The structure of MSK starch amylopectin was higher in B1 and B2 chains but lower in A chain than that of other starch amylopectins. According to the physical properties, most MSK starch granules were in an oval shape and had a size in the range of 13.0 – 13.3 µm which were smaller than corn and tapioca starch granule, but larger than rice starch granule. MSK starch exhibited an A type X-ray pattern and possessed higher in relative crystallinity than other starches. Physicochemical properties of MSK starches were significantly different from those of other starches. In thermal properties study, MSK starches exhibited higher in onset temperature (To) and gelatinization enthalpy ( Hgel) than other starches. However, they required lower amount of energy (Hamylose-lipid) to melt the structure of amylose-lipid complex than other starches, excluding tapioca starch. Amylopectin of MSK starches had a higher degree of retrogradation than other starch, excluding Chiang Phatthalung rice starch. MSK starch granules illustrated a higher in swelling power and solubility than corn starch and rice starch granules. In accordance with swelling power and solubility, MSK starches had a higher pasting temperature (excluding Chiang Phatthalung rice starch) and a higher peak viscosity (excluding tapioca starch) than other starches. However, MSK starch pastes had setback in viscosity lower than other starches and quiet low in breakdown in viscosity. Texture profile analysis showed that MSK starch gels were higher in hardness, springiness and gumminess than other starches. According to the physicochemical properties different from other starches, it could be concluded that all MSK starches from three mango cultivars had a strong granular structure resulting in a difficulty in gelatinization. Furthermore, the MSK starch molecules were likely to retrograde and produced a hard gel. Among three cultivars, Kaew MSK starch clearly exhibited these physicochemical properties more than Chokanun and Namdokmai MSK starches, respectively