Using Short-Wave Infrared Radiation to Improve Aqueous Enzymatic Extraction of Peanut Oil: Evaluation of Peanut Cotyledon Microstructure and Oil Quality

In this study, the effects of short-wave infrared radiation (SIR) on enzyme-assisted aqueous extraction process (EAEP) of peanut oil (PO) are investigated, including peanuts cotyledon cells mircrostructure and yield as well as quality of extracted PO. GC-flash electronic nose (EN) combined with principal components analysis (PCA) is applied to select conditions for SIR process. The appropriate roasting condition based on the overall flavor is determined as 150 degrees C for 55min. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to investigate the effects of SIR on cotyledon microstructure. The results demonstrated that SIR damaged the cell microstructure and oil body membrane, and the extraction of oil is facilitated. Accordingly, the oil yield increased significantly by 8.74% compared to that of the control (p<0.05). Further analysis on the quality properties of PO revealed that the content of polyphenols of oil extracted from SIR roasted peanuts (2.790.05mg GAEkg(-1)) is 62.21% higher than that from the control. It is in consistent with the significantly enhanced oxidation stability of oil in the present study (p<0.05). Furthermore, the variety and relative content of volatile compounds which contributed to a better overall flavor are greatly increased.Practical Applications: SIR as a mild and efficient roasting method could enhance the oil extraction yield in EAEP and improve the oxidation stability of the extracted oil. With the appropriate pre-roasting of peanuts by SIR, the overall flavor of EAEP extracted peanut oil was improved. Its volatiles pattern was close to that of the commercial hot-pressed PO. It was confirmed that SIR is a novel choice for roasting processing, as well as a potential and available pre-roasting method of peanuts to improve the EAEP technology. In order to improve the enzyme-assisted aqueous extraction process (EAEP) of peanut oil, short-wave infrared radiation (SIR) to roast peanuts before the extraction process is used. SEM and TEM are employed to evaluate the roasting effects on cotyledon microstructure. Some chemical properties, the content of antioxidant compounds, and the flavor of extracted oil are assessed to show the effects on oil quality. The oil yield is also evaluated to explain the roasting effects together with the changes of the microstructure.