The Effect Of Maillard Reaction On The Quality Of Dried-Seasoned Squid During Storage And Application Of Electron Beam Irradiation Technology

As a kind of dried seafood, dried-seasoned squid have the characteristics of great taste, delicious flavor, and because it belongs to high-protein and low-fat nutritional food, so it is very nutritional and popular in the world. But according to some studies, the quality of dried-seasoned squid gradually descended during storage period. Nutritional ingredients, such as protein, amino acid, sugar and moisture significantly reduced. The physical and chemical indexes, such as trimethylamine oxide (TMAO), color and volatile base nitrogen (TVB-N) were easily changed, the number of microbe increased significantly. So there are many problems of quality and safety in dried-seasoned squid during storage time. On the basis of quality in dried-seasoned squid at25℃during storage time, and according to the change rules and differences on nutrition, physical and chemical properties and microbial indicators, the research emphatically analyzed the influence of Maillard browning reaction on dried-seasoned squid, then set up an evaluated model about quality of the dried-seasoned jumbo squid and neon flying squid during storage time at room temperature. According to the experiment of simulation system in vitro, we discussed the effect of Maillard reaction productions to promote TMAO decomposite to DMA and FA. At the end, according to exploring the effect of electron beam irradiation technology on the quality of dried-seasoned squid during the storage period, we used electron spin resonance (ESR) spectroscopy to analyse failure of free radicals, then got the following conclusion:1. During storage period in dried-seasoned jumbo and neon flying squid moisture loss, protein degradation, lipid oxidation and Maillard browning reaction were occurred, and browning intensity increased111%and96%, the color in two kinds of squids differed distinctly, in which a*value rose by85%and45%, respectively. The high level of reducing sugar in the dried-seasoned jumbo squid resulted from the addition of lactose and glucose in the processing, the level of lactose decreased rapidly during whole storage, while the levels of glucose exhibited a slow increase after a sharp decline. Correspondingly, the amount of galactose increased remarkably after the original30d in dried-seasoned jumbo squid. Additionally, only low amount of glucose was detected in neon flying squid, which decreased slowly, and total reducing sugar content decreased by40%and34%, respectively. In jumbo squid product, the reductions of the major constituents such as Lysine (Lys), Glutamic acid (Glu), Tyrosine (Tyr), Phenylalanine (Phe) and Proline (Pro) were more pronounced, with about25-19%mass loss rate. Whereas, Pro, Glycine (Gly), Histidine (His), Glu and Lys in the neon flying squid decreased19-13%compared with the initial product. The TMAO levels decreased44%and25%in dried-seasoned jumbo and neon flying squid respectively during storage. Correspondingly, the levels of DMA, FA and F-FA increased about6,7,1-fold in the jumbo squid, while the amount of DMA, FA and F-FA rose about2,2,0.3-fold in the neon flying squid compared to the initial levels. The content of TVB-N is higher in dried-seasoned jumbo squid during storage time, we suggested that Maillard reaction products (MRPs) in squid product could induce decomposition of TMAO during storage. Bacteria increased slowly in dried-seasoned squid, the population of APC increased from3.66and3.11log CFU/g to4.07and3.76log CFU/g after150days of storage in jumbo squid and neon flying squid product, respectively. Additionally, conforms was detected only in jumbo squid product after30days, then increased greatly to2.54log CFU/g. After that we set up an evaluation model about quality of the dried-seasoned jumbo and neon flying squid during storage time at room temperature.2. Firstly, we used four kinds of amino acids [Glu, Lys, Arginine (Arg), Aspartic acid (Asp)] and lactose/glucose to produced MRPs, we studied the characteristics of MRPs, including UV-absorbance at294nm, browning intensity and antioxidant activity (reducing powder and DPPH radical scavenging activity), it suggested that the browning and antioxidant activity were higher in the MRPs than that of single reducing sugar or amino acid. In the present study, the MRPs derived from glucose or lactose-Lys,-Arg showed the strongest browning intensity, antioxidant activity and reducing sugar consumption. The effect of MRPs on the breakdown of TMAO in the TMAO aqueous solution and jumbo squid supernatant was analyzed next, we found that the thermal degradation of TMAO to DMA and FA significantly accelerated in the presence of MRPs derived from glucose or lactose-amino acid during the thermal process. The MRPs of glucose/lactose-Lys promoted the thermal decomposition of16%and33%TMAO in the TMAO aqueous solution and jumbo squid respectively, which was stronger positive effect. Under the condition of high temperature and25℃, we chose MRPs of Glc-Lys, Lac-Arg, Lac-Lys, which have the strongest antioxidant activity, then analyzed the effect in decomposing TMAO, the result showed MRPs of Lac-Lys is most obvious. Thus, we speculated that MRPs may accelerate the TMAO decomposition process.3. Compared with control group, the electron beam groups of2kGy and4kGy could not significantly affect moisture, protein, acid value, water activity and the level of color in the dried-seasoned jumbo squid, but in the storage period after electron beam irradiation processing, in the samples moisture loss, protein decomposition, acid value growth, the change rate of total reducing sugar, degradation rate of TMAO were reduced, and electron beam treatment could also significantly reduce the initial number of APC in the dried-seasoned jumbo squid, the number of APC could be reduced1-2log CFU/g. Electron beam treatment could significantly reduce coliforms during storage, and moulds could not be detected. And the higher dose, the more effective. But at the beginning of the storage, electron beam processing can promote the generation of TVB-N, but it rose much more slowly in the storage time. Electron beam irradiation treatment would lead to produce free radicals signals in dried-seasoned squid, and the more dose, the signal is more higher. With extended storage period, the free radical signals became weaker. Therefore, on the one hand, the ESR spectroscopy detection technology of free radical signals can be used to evaluate the efficacy of the different doses of radiation processing, meanwhile, on the other hand, it can be used as a method to test sample whether was irradiated.