Quality Formation of Adzuki Bean Baked: From Acrylamide to Volatiles under Microwave Heating and Drum Roasting

Abstract

Baked adzuki beans are rich in tantalizing odor and nutritional components, such as protein, dietary fiber, vitamin B, and minerals. To analyze the final quality of baked beans, the acrylamide and volatile formation of adzuki beans were investigated under the conditions of microwave baking and drum roasting. The results indicate that the acrylamide formation in baked adzuki beans obeys the exponential growth function during the baking process, where a rapid increase in acrylamide content occurs at a critical temperature and low moisture content. The critical temperature that leads to a sudden increase in acrylamide content is 116.5 °C for the moisture content of 5.6% (w.b.) in microwave baking and 91.6 °C for the moisture content of 6.1% (w.b.) in drum roasting. The microwave-baked adzuki beans had a higher formation of the kinetics of acrylamide than that of drum-roasted beans due to the microwave volumetric heating mode. The acrylamide content in baked adzuki beans had a significant correlation with their color due to the Maillard reaction. A color difference of 11.1 and 3.6 may be introduced to evaluate the starting point of the increase in acrylamide content under microwave baking and drum roasting, respectively. Heating processes, including microwave baking and drum roasting, for adzuki beans generate characteristic volatile compounds such as furan, pyrazine, ketone, alcohols, aldehydes, esters, pyrroles, sulfocompound, phenols, and pyridine. Regarding flavor formation, beans baked via drum roasting showed better flavor quality than microwave-baked beans.

Effect of Microwave Treatment on Adzuki Beans (Vigna angularis L.) under Dry State—Analyzing Microstructure, Water Absorption, and Antioxidant Properties

“…The color changes were associated with Maillard reactions and caramelization during heating, and Krysiak et al [ 26 ] suggested the physical and chemical changes of the bean, depending on the temperature, as follows: (1) tissue destruction and structural changes, including protein denaturation at 50–60 °C; (2) non-enzymatic browning and water evaporation of bean seed over at 100 °C; (3) thermal decomposition into volatile compounds, as well as caramelization, oxidation, and esterification above 180 °C. Yao et al [ 27 ] suggested that the overall color of the adzuki beans showed a sharp decline, due to the thermal accumulation inside the baked beans resulting from microwave heating ( p < 0.05), which caused an obvious Maillard reaction in the adzuki beans in a short time.…”

“…The increase in TPC and TFC is thought to be due to the generation of aminocarbonyl reaction products, such as melanoidin, which have a high free radical scavenging ability because of heat generated by microwaves. Yao et al [ 27 ] reported that the heating process leads to precursors of volatile substances, and the thermal decomposition of oligosaccharides generates reducing sugars. Consequently, a reaction between the free amino acids and reducing sugars releases furans, pyrazines, etc.…”