Chemical Characterization, Antioxidative Capacity And Isolation Of Maillard Reaction Products From Shrimp Peptides

In recent years, how to make full use of an increasing amount of shrimp wastehas been attracting attention from the aquatic processing industry. This paper used theshrimp waste as material and made it the Shrimp Peptides（SP） using Alcalaseenzyme, then Maillard reaction（MR）was made to occur between SP and Glucose atdifferent temperatures for a series of times in order to study the effects of temperatureand time on the evlolution of Maillard reaction and the antioxidative capacity of itsproducts（Maillard reaction products, MRPs）as well. The whole work was outlinedbelow.1. The effects of reaction conditions on the evolution of Maillard reactionThe effects of heating temperatue and time on the sensory evaluation, browningdevelopment, A294nmand free amino groups contents of MRPs: For MRPs-100andMRPs-110, the browning development and A294nmN S’Y change much within the first1h, but grew fast thereafter. Both browning intensity and A294nmwere found to besignificantly different between MRPs-100and MRPs-110from2h (P≤0.05). the freeamino groups of MRPs-100and MRPs-110decreased fast during the initial2h,resulting in the23.43%,33.37%decrement at the time of2h respectively, the suddenand rapid decrement of free amino groups of MRPs in the initial2h suggested thatMaillard reaction occurred promptly between SP and glucose as soon as heating treatment began. Additionally, Maillard reaction succeeded in enhancing the Shrimparoma and characteristic burning smell while significantly lowered the bitternesswhich was inherent in SP.We measured the change of molecular weight distribution（MW）, furosinecontent, and HMF content of MRPs as a function of heating temperature and time,FMAAs was also tried to be identified from MRPs. As a result, for MRPs-100andMRPs-110，the high molecular weigh（tHMW,>500Da）fractions increased with theincreasing temperure and prolonged time, correspondingly, the low molecular weight（LMW,<500Da）contents decreased, the former was mainly attributed to thepeptides crossing linked between amino acid residue and carbonyl of glucose by theMR, and the latter was owning to the consumption of small peptides and free aminoacids.As to the SP heated alone (SP-100and SP-110), HMW contents decreased andLMW contents increased with the higher temperature and longer heating time, whichwas mainly because heating treatment degraded the peptides into smaller ones. Fromthe result above, heating treatment made two change of the MW of the MRPsmixtures at the same time, one was MW went larger due to peptide-crossing, the otherwas MW went smaller due to peptides degradation. In both MRPs-100and MRPs-110，furosine content increased in the intial heating stage and then went down, while HMFamount kept growing during the whole heating process. LC-MS system managed toidentify4kinds of FMAAs from MRPs (110℃,2h), namely FM-Leu, FM-Ile,FM-Val,-FM-Lys、ε-FM-Lys（furosine）, which suggested such amino acids wasable to involve in the Amadori compounds formation during the MR.2. Study on the antioxidative capacity of MRPs and its inhibition effects on thesoybean oil oxidation. Several kinds of antioxidative methods（DPPH、FRAP、ABTS、ORAC）wereemployed to evaluate the antioxidative capacity of MRPs, and Fe2+chelating activityof MRPs was also measured. In adiition, MRPs were applied to inhibit the oxidationof soybean oil in emulsion system. As a consequence, Maillard reaction was able toconsiderably enhance the antioxidative capacity of SP irrespective of the antioxidativemethods mentioned above, furthermore, the higher temperature or the longer heatingtime, the better was the antioxidative ability of MRPs. Otherwise, the Troloxequivalent of the antioxidative capacity of MRPs acquired by different methods werestatistically different, which was due to the different mechanisms they were involved.As for the Fe2+chelating activity of MRPs, with increasing temperature andextending heating time, it increased until2h at100℃or1h at110℃, then both wentdown, this change pattern might be correlated to the decreasing of free amino groupsduring the MR. SP, MRPs were both able to prolong the induction period and cut theoxidization rate of oil, among which MRPs-10010，MRPs-1101，MRPs-1102werethe best.3. The effects of MRPs and its fractions on the oxidative response level of HepG2MTT test suggested that SP, MRPs and its fractions shown no toxicity to HepG2cell. When HepG2cell was exposed to oxidative stress, both the lipid peroxidationlevel of cell membrane（MDA）and intracellular active oxygen（ROS）increasedsignificantly, when SP or MRPs was added at the concentration of over500μ/R，the MDA and ROS level was brought down significantly. Among all the test samples（SP,100-5,100-10,110-5,110-10）,110-5MRPs shown the best capacity to bringdown the MDA and ROS level of HepG2cell. Then110-5MRPs was separated into4fractions with different molecular weights, their antioxidative capacity (ORAC)，browning development, A294nmand furosine contents were analysized, the result shown: The antioxidative ability（ORAC）was in order: Fraction1> Fraction3>Fraction2> Fraction4, and it was positively correlated with their browningdevelopment, but negatively correlated with Furosine content, otherwise, in theHepG2cell oxidative stess pattern, their ability to alleviate the stress response of cellwas in order: Fraction3> Fraction2> Fraction1> Fraction4.