Aroma-Active Compounds in Jinhua Ham Produced with Different Fermentation Periods
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Molecules 2014, 19, 19097-19113; doi:10.3390/molecules191119097 OPEN ACCESS molecules ISSN 1420-3049 www.mdpi.com/journal/molecules Article Aroma-Active Compounds in Jinhua Ham Produced With Different Fermentation Periods Xiao-Sheng Liu, Jian-Bin Liu, Zheng-Mao Yang, Huan-Lu Song *, Ye Liu and Ting-Ting Zou Laboratory of Molecular Sensory Science, College of Food and Chemical Engineering, Beijing Technology and Business University, Beijing 100048, China; E-Mails: [email protected] (X.-S.L.); [email protected] (J.-B.L.); [email protected] (Z.-M.Y.); [email protected] (Y.L.); [email protected] (T.-T.Z.) * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel./Fax: +86-10-6898-4025. External Editor: Derek J. McPhee Received: 12 September 2014; in revised form: 21 October 2014 / Accepted: 5 November 2014 / Published: 19 November 2014 Abstract: The aroma-active compounds in Jinhua ham processed and stored for 9, 12, 15 and 18 months were extracted by dynamic headspace sampling (DHS) and solvent-assisted flavor evaporation (SAFE) and analyzed by gas chromatography-olfactometry-mass spectrometry (GC-O-MS). In GC-O-MS, volatile compounds were identified based on their mass spectrum, linear retention index (LRI), odor properties, or reference compound comparisons. The results showed that a total number of 81 aroma-active compounds were identified by GC-O-MS. Among them, acids (such as acetic acid, butanoic acid and 3-methylbutanoic acid), saturated aldehydes (such as hexanal, heptanal, octanal and 3-methylbutanal), benzene derivatives (such as benzeneacetic acid), ester and lactone (such as γ-nonalactone and γ-decalactone) were identified as critical compounds in Jinhua ham aroma. The results also indicated that the type and content of the odorants increased significantly with the duration of the fermentation period. Keywords: Jinhua ham; aroma-active compounds; GC-O-MS; DHS; SAFE Molecules 2014, 19 19098 1. Introduction Dry-cured ham is generally classified based on the origin. In particular, the three main forms from southern China, southern or central Europe and the southeastern United States, have many differences in their sensory properties [1]. Jinhua ham, Parma ham, Iberian ham and the American ham are their best known representatives [2–5]. In China, Jinhua ham, along with “Xuanwei ham” and “Rugao ham”, are well known as the “three hams”. The traditional processing technology for making Jinhua ham is composed of multiple steps, including raw material selection, salting, soaking and washing, sun drying and shaping, fermentation, ripening, post-ripening, grading and storage [6]. The unique flavor of Jinhua ham is appreciated by consumers all over the world. Nowadays, ham quality is graded by its aroma intensity and persistence on the bamboo stick, but different processing technologies can make a great difference in the flavor quality of ham. Therefore, the control of ham flavor formation during processing is very important for ham grading, so comprehensive research of Jinhua ham flavor is crucial for better ham quality and the establishment of a national traditional meat products standard. In the fermentation process, relevant chemical and biological reactions take place in the muscle of Jinhua ham, such as lipid degradation and oxidation, Maillard reactions, Strecker degradation, etc., resulting in the special ham flavor [7]. Many exploration methods and technologies have been used to analyze the odorants in Jinhua ham, including dynamic headspace sampling (DHS) [8], purge-and-trap (P&T) [9], solid phase microextraction (SPME) [10], but to our knowledge, there are few studies on the identification of variations of key odorants of Jinhua ham at different fermentation stages, compared to that of Western dry-cured hams such as Parma and Iberian ham [11–16]. The objective of this study was to identify and characterize the aroma-active compounds of Jinhua ham under different processing times and operation conditions by gas chromatography-olfactometry-mass spectrometry (GC-O-MS), aided by both dynamic headspace dilution analysis (DHDA) and aroma extract dilution analysis (AEDA) techniques. 2. Results and Discussion 2.1. Aroma-Active Compounds A total of 81 aroma-active compounds of Jinhua ham in different processing time were identified by DHS-GC-O-MS and SAFE-GC-O-MS. The compounds included 15 saturated and unsaturated aldehydes (Figure 1), 11 ketones (Figure 2), 12 alcohols (Figure 2), 11 acids (Figure 3), 11 esters and lactones (Figure 3), five sulfides (Figure 4), seven benzene derivatives compounds (Figure 4), three pyrazines and six others (Figure 4). 2.2. Key Aroma-Active Compounds by Dynamic Headspace Dilution Analysis (DHDA) Sixty-seven compounds were identified as odorants by DHS-GC-O-MS (Table 1) and eight compounds remained unknown. Among the identified compounds, 3-methylbutanoic acid (odor: sour and sweaty), 2-acetyl-1-pyrroline (odor: popcorn), trimethylamine (odor: fishy) and γ-nonalactone (odor: peachy and sweet) had average FD factors over one hundred (where Average FD factor = Sum of the FD factors in one compound of 18, 15, 12 and 9 months ham/4). Seven other identified compounds: Molecules 2014, 19 19099 acetic acid (odor: sour), hexanal (odor: cut-grass), 2,6-dimethylpyrazine (odor: toast and nutty), butanoic acid (odor: cheesy), methional (odor: cooked potato), γ-decalactone (odor: peachy and burnt sugar) and 1-nonen-3-one (odor: mushroom) had average FD factors ≥ 50. Figure 1. Structures of the saturated and unsaturated aldehydes in Jinhua ham. Figure 2. Structures of the ketones and alcohols in Jinhua ham. Figure 3. Structures of the acids, esters and lactones in Jinhua ham. Molecules 2014, 19 19100 Figure 4. Structures of the sulfides, benzene series compounds, pyrazines and other compounds in Jinhua ham. Table 1. Aroma-active compounds in Jinhua ham by DHS. R.I. c FD f Nr a Compound Name b Identification d Odor Property e R.I.(DB-5ms) R.I.(DB-WAX) 18 15 12 9 c 38 methanthiol - 627 RI,O rotten egg 25 125 1 - 76 trimethylamine 503 848 RI,O,MS fishy 125 125 125 25 50 ethyl acetate 610 877 RI,O,MS,STD fruity/sweet 25 25 1 - 2 3-methylbutanal 638 927 RI,O,MS chocolate/malty 25 125 5 1 27 ethanol - 941 RI,O,MS,STD alcohol 1 1 - - 77 triethylamine 677 970 RI,O,MS fishy 25 25 - - 17 2-pentanone - 971 RI,O,MS fruity 5 25 - - 3 pentanal 700 984 RI,O,MS fermented/yoghourt 25 5 5 - 54 2-methyl-butanoic acid ethyl ester 850 1051 RI,O,MS fruity/sweet 25 5 5 1 51 acetic acid butyl ester 812 1059 RI,O green/fruity 5 5 - - 18 2-methyl-3-pentanone - 1068 RI,O,MS mint 25 5 - - 61 disulfide, dimethyl 750 1079 RI,O,MS cooked cabbage/onion 25 25 1 1 4 hexanal 803 1094 RI,O,MS,STD cut-grass 125 125 25 5 32 1-methoxy-2-propanol - 1137 RI,O,MS plastic 1 1 1 1 33 1-penten-3-ol 688 1164 RI,O,MS,STD buttery/grassy/green 5 1 - - unknown - 1179 RI,O,MS popcorn 5 25 - - 5 heptanal 905 1183 RI,O,MS oily/green 25 5 1 - 78 D-limonene 1028 1191 RI,O,MS,STD sweet /orange 5 25 5 - 79 pyridine 757 1193 RI,O,MS spicy 1 1 1 1 unknown - 1199 O cooked potato 25 125 1 - 30 3-methyl-1-butanol - 1201 RI,O,MS fermented/oily/fruity 5 - - - 80 2-pentylfuran 995 1231 RI,O,MS,STD fruity/green 5 5 - - 52 hexanoic acid ethyl ester 1000 1232 RI,O,MS fruity/apple - - 5 1 28 1-pentanol 760 1250 RI,O,MS green 1 5 - 1 10 (E)-2-hexenal 855 - RI,O,MS green/fatty 5 5 - - unknown - 1270 O popcorn 125 125 5 - 6 octanal 1009 1287 RI,O,MS fatty 5 5 1 1 22 3-octen-2-one 1045 1285 RI,O,MS fatty/nutty/spicy 25 125 - - Molecules 2014, 19 19101 Table 1. Cont. R.I. c FD f Nr a Compound Name b Identification d Odor Property e R.I.(DB-5ms) R.I.(DB-WAX) 18 15 12 9 c 20 3-hydroxy-2-butanone 722 1286 RI,O,MS buttery/green 5 5 1 - 21 1-octen-3-one 980 1297 RI,O,MS,STD mushroom 125 125 5 5 19 1-hydroxy-2-propanone 680 1307 RI,O,MS nutty/bitter - - 1 5 11 (E)-2-heptenal 961 1317 RI,O,MS,STD fatty/fruity 25 25 - - 81 2-acetyl-1-pyrroline 912 1339 RI,O,STD popcorn 625 125 125 25 unknown - 1345 O fishy 25 25 - - 73 2,6-dimethylpyrazine 919 1337 RI,O,MS,STD toast/nutty 125 125 25 5 63 dimethyl trisulfide - 1380 RI,O,MS garlic/cooked cabbage 125 25 5 - 74 trimethylpyrazine 1006 1395 RI,O,MS,STD nutty/chocolate 25 5 1 1 23 1-nonen-3-one - 1404 RI,O,MS mushroom 25 5 1 - 7 nonanal 1102 1408 RI,O,MS green/fatty/soapy 25 1 5 - 36 3,5-octadien-2-ol - 1408 RI,O,MS green 1 - - - 12 (E)-2-octenal 1064 1425 RI,O,MS fatty 25 5 - - 75 tetramethylpyrazine 1084 - RI,O,MS,STD nutty 1 - - 1 34 1-octen-3-ol 986 1445 RI,O,MS mushroom 5 25 25 25 39 acetic acid 658 1446 RI,O,MS,STD sour 125 125 25 25 9 methional 906 1450 RI,O cooked potato 125 125 25 - 8 furfural - 1453 RI,O,STD sweet popcorn/wood 125 25 - - 26 camphor 1145 1503 RI,O,MS camphor 5 1 1 - 47 2-methylpropanoic acid 828 1550 RI,O,MS sock/stinky 25 125 1 1 66 benzaldehyde 969 1515 RI,O,MS almond 5 5 - - 24 (E,E)-3,5-octadien-2-one 1091 1520 RI,O,MS fatty 5 - 1 - 40 propanoic acid 718 1556 RI,O,MS sour 25 25 - - unknown - 1559 O chocolate 25 1 1 - 37 2,3-butanediol 783 1581 RI,O,MS fruity/creamy/oily - - 5 25 14 (E,Z)-2,6-nonadienal - 1586 RI,O cucumber 1 1 1 - 35 (E)-2-octen-1-ol - 1607 RI,O,MS mushroom - 5 - - 55 butyrolactone 950 1613 RI,O,MS hay 5 25 1 - unknown - 1617 O rancid/fishy 125 125 - - 41 butanoic acid 821 1630 RI,O,MS cheesy 125 125 25 5 56 γ-pentalactone - 1632 RI,O,MS creamy 25 1 - - 53 decanoic acid, ethyl ester - 1637 RI,O,MS fruity 5 1 - 1 67 acetophenone 1078 1612 RI,O,MS flower/sweet - - 1 1 48 3-methylbutanoic acid 876 1667 RI,O,MS sour/sweat 625 625 625 125 13 (E,E)-2,4-nonadienal 1155 1703 RI,O,MS fatty/fried 5 1 - - 57 γ-hexanolactone 1062 1705 RI,O,MS hay/sweet 25 1 - - 42 pentanoic acid 911 1714 RI,O,MS meat/rancid 125 25 1 1 65 2-acetyl-2-thiazoline - 1759 RI,O popcorn 1 5 5 - 15 (E,E)-2,4-decadienal - 1812 RI,O,MS,STD fatty/fried 5 - 1 - 43 hexanoic acid 997 1833 RI,O,MS sour/rancid 5 1 - - 71 4-methylguaiacol - 1938 RI,O mushroom/smoke 25 5 - - 58 γ-nonalactone 1124 2023 RI,O peachy/sweet 125 125 125 25 72 p-cresol - 2031 RI,O fecal 125 25 25 1 Molecules 2014, 19 19102 Table 1.