Rapid Assessment Of Freshness Degree Of Lotus Seeds Based On Direct Mass Spectrometry

Lotus seed is rich in nutrients, has been known as a notable folk medicine and edible food source. However, lotus seeds are easy to aging, and their quality and taste deteriorated quickly during storage. Recently, the qualities of lotus seeds on the market differed greatly, and it is hard to distinguish the aged lotus seeds from the fresh one. The traditional analysis methods often required tedious sample preparation, and it wastes a lot of labor and material resources, it is difficult to meet the requirement of lotus seed samples in situ, fast, accurate high-throughput analysis. Direct mass spectrometry is a new technique developed rapidly in recent years, the wider application to large field. Herein, Surface desorption atmospheric pressure chemical ionization mass spectrometry (SDAPCI-MS) and Extractive electrospray ionization mass spectrometry (EESI-MS) was directly used to measure lotus sample, and be screened by chemometric methods for the quality of the lotus seeds. The main contents and results were as following up:1、In order to differentiate the freshness of lotus seeds on the market for rapid direct identification. SDAPCI-MS detected the fresh and aged lotus seeds slice surface directly. Both in the positive and negative ion detection mode, mass spectra characteristics of fresh and aged lotus seeds showed that, SDAPCI was able to withstand the impact of the complex matrix of lotus seeds which contained substances nuances. The fingerprint spectrometry of different lotus seeds were further analyzed by principal component analysis (PCA) together with back propagation artificial neural network (BP-ANN), the results showed that, in positive ion detection mode, the accuracies of2012,2011,2010,2009lotus seeds test samples were90%,85%,85%and90%respectively, and the accuracies of fresh and aged lotus seeds samples were92.5%and91.7%. In negative ion detection mode, the accuracies of2012,2011,2010,2009lotus seeds test samples were90%,85%,85%and90%, and the accuracies of fresh and aged lotus seeds samples were95%and92%. Combination of SDAPCI-MS and the chemometric methods allows an accurate screening of fresh from aged lotus seeds.2、The EESI-MS mass spectrometry conditions were optimized by ionizing voltage, ion transfer tube temperature, sample injection flow rate. The results indicated that the best conditions of MS for the detection of the ion of m/z625of ionization voltage, ion transfer tube temperature, and sample injection flow rates were3.5kV,250℃,5μl/min respectively. Lots of alkaloids were detected in the ethanol extract of lotus seeds such as liensinine, neferine, lotusine, nuciferine, O-nuciferine.3、EESI-MS mass spectrometry was also applied to the oligosaccharides research by the lotus seeds aqueous extract, and the principal component analysis was used to analyze the different year lotus chemical fingerprint spectra. The results manifested that lotus aqueous extract are rich in oligosaccharides content, EESI-MS combined with PCA, and oligosaccharides contents have a great contribution for the differentiate fresh lotus seeds and aged one, and classification of different years lotus seeds by PCA. EESI provides a new method for the rapid ionization mass spectrometry to the identification of food quality and safety.In this paper, we used self-made SDAPCI and EESI mass spectrometry as a research platform, which give a systematic study of different year lotus sample, it also established of a simple, rapid, sensitive detection of lotus seeds, these techniques were expected to give more contribution to the safety of food quality.