Study On The Flavor Of Jinhua Ham And Parma Ham

With improvement of the economy and living standards in our country, consumers have become conscious of their health and are now consuming greater quantities of high quality ham product. Flavor is one of the important indexes of dry-cured ham's quality. The research on characteristic flavor compounds of dry-cured hams can provide theoretical sense and applicational value.Jinhua ham and Parma ham were used to identify the aroma-active compounds and taste-active compounds, and moreover, the taste-active peptide was prepared by enzyme hydrolysis from two hams, the correlation of taste-active peptide's structure and characteristics were finally studied. Main content of this paper was as following.Volatile compounds from the Jinhua ham and Parma ham by simultaneous distillation extraction (SDE) and solid-phase microextraction (SPME) methods respectively, and identified by the gas chromatography-mass spectrometry. Results showed that the alcohols, aldehydes, ketones, esters, hydrocarbons, sulphur-contained and heterocyclic compounds were the common components. Twelve compounds among them 3-methyl-butanal, pentanal, hexanal, heptanal, benaldehyde, and 2-octenal were all identified by the two techniques. There were more aldehydes and acids but less hydrocarbons and alcohols in Parma ham. Comparing differences in extraction methods, there were more acids and alcohols in Jinhua ham and Parma ham by SPME and SDE respectively.The intention of this research was to characterize the aromatic compounds of the two hams as extracted by SPME and SDE respectively. In Jinhua ham, four new aroma-active compounds were found, (E)-2-octenal,hexadecanal,octanoic acid and 3-methyl- ethyl butyrate, and two new aroma-active compounds were found in Parma ham, octadecadienoic acid ethyl ester and 2,3-dihydroxy-hexadecanoic acid propyl ester. The OSME (a Greek word) showed that the SPME extract could be described as cured, green/grassy, fruity and burnt compared to fatty, meaty, roast, cured and caramel for the SDE one. The Aroma Extract Dilution Analysis (AEDA) suggested that 1) (z)-2-heptenal as the main source of fatty odor for the fully cooked ham; 2) 3-(methylthio)- propanal, 2, 6-dimethyl-pyrazine and 2-pentyl-furan for the meaty odor; 3) 3-(methylthio)-propanal, 2, 6-dimethyl-pyrazine and (E, E)-2, 4-decadienal for the roast odor; and 4) 2-pentyl- furan as the main source of cured odor.The effect of three traditional cooking methods, steaming (B), boiling (C) and stewed ham soup (S) on the volatiles in Jinhua ham was evaluated which was identified by SPME-GC-MS and the flavor profile detected by electronic nose analysis (EN). Results from the principal components analysis (PCA) showed A, B1, B2, C1 and C3 had same volatiles, while B3, C2 and S1 , S3; S2 showed negative correlation with A, C1, C3, B1 and B2. Most importantly, many unsaturated hydrocarbons, such as 3-methyl-2-butenal, 2-heptenal were generating by different types of heating. The EN analysis indicated that C2 appeared to have profile similar to the raw ham; however, C3 had different flavor profile from that for S1 and S2. The main source of the difference was that profiles appeared to be high in sulfur-containing content in S1 and S2.The main taste compounds of the water-soluble extract (WSE) of dry-cured ham were extracted with warm water, HCl-ethanol, ethanol, alkaline and boiled water as solvent. Results showed the WSE of Jinhua ham extracted using warm water, had the highest percentage (19.57%) of the peptides with molecular weight of 200-300 Da. Most important it was most similar in taste characteristics to the raw ham during the sensory evaluation; with salty and sweet taste. In addition, the recovery of peptides was high (36.11%), though the alkaline method was much more effective for extraction (37.05%), the astringent taste dominated during the sensory evaluation. Otherwise, from the viewpoint of FAAs, we could see they mainly provided the umami taste. Considering the interactions between taste compounds and the aroma compounds, the latter obtained using the five methods were identified and significant differences were noted.The single factor test and response surface analysis was used water insoluble substance of Parma Ham was hydrolyzed. Results indicated that the optimum conditions were reaction temperature 60oC, starting pH 7.45 and the dose of Protamex 2.34% and Flavorzyme 4.17%, and adding two enzymes simultaneously. Under these conditions, crude peptide content was 76.55%, the molecular weight of enzyme-hydrolysate was mainly 200-1,000 and the proportion of small peptide was high about 93%. Moreover, the hydrolysate had the highest scores in the taste of sensory evaluation without any bitterness.Fractions of seven taste-active peptides were obtained by gel filtration chromatography, semi-preparative RP-HPLC chromatography and analytical RP-HPLC chromatography. The amino acid sequences of 7 peptides were gained using MS/MS analysis. It was found that one positive charge amino acid was included in the sequence of peptides, with the highest appearance incidence of Asn, which was in accordance with the umami peptide. They were all synthetic produced and the taste activity was verified. The peptide with the sequence of Ala-His-Ser-Val-Arg-Phe-Tyr and Asn-Gly-Lys-Glu-Thr were verified with the ham taste. In addition, Ala,Arg,Glu,Gly,Na⁺,K⁺,Cl^-,PO₄^3- were also identified to have great contribution on the characteristic taste of ham.