渔业科学进展  2024, Vol. 45 Issue (3): 245-257  DOI: 10.19663/j.issn2095-9869.20230314002


耿海永, 陈丽华, 杨方, 吴仪, 王淑芬, 姜启兴, 许艳顺, 夏文水. 白鲢鱼糜低气味本底模型的构建研究[J]. 渔业科学进展, 2024, 45(3): 245-257. DOI: 10.19663/j.issn2095-9869.20230314002.
GENG Haiyong, CHEN Lihua, YANG Fang, WU Yi, WANG Shufen, JIANG Qixing, XU Yanshun, XIA Wenshui. The Construction of a Low-Odor Background Model of Silver Carp (Hypophthalmichthys molitrix) Surimi[J]. Progress in Fishery Sciences, 2024, 45(3): 245-257. DOI: 10.19663/j.issn2095-9869.20230314002.




耿海永, E-mail: haiyonggeng@163.com


杨方, 副研究员, E-mail: yangfang_8_9@126.com


耿海永 , 陈丽华 , 杨方 , 吴仪 , 王淑芬 , 姜启兴 , 许艳顺 , 夏文水     
江南大学食品科学与技术国家重点实验室 江南大学食品学院 江苏省食品安全与质量控制协同创新中心 江苏 无锡 214122
摘要:鱼糜制品(如火锅鱼丸)的风味是消费者关心的质量属性之一,而关键气味活性物质的吸附释放规律并不明确。现有气味研究主要在配置溶液中进行,与真实的气味活性物质—固态鱼糜之间的相互作用存在一定差异,因此,基于固态鱼糜进行气味研究是十分必要的,其关键在于一个无气味或低气味的鱼糜本底模型,从而可进一步研究各气味成分与鱼糜本底模型的互作关系。本研究考察了8种不同漂洗介质对鱼糜本底模型气味残留的影响。结果表明,白鲢(Hypophthalmichthys molitrix)鱼糜经SPME-GC-MS共检出65种挥发性物质,气味活性物质(OAV>1)有18种;经8种漂洗介质处理后,鱼糜样品中分别含有6、8、7、9、6、12、9和9种气味活性物质,挥发性气味物质的残留率依次为(0.380±0.120)%、(0.610±0.086)%、(0.280±0.033)%、(0.480±0.037)%、(0.150± 0.018)%、(4.330±0.160)%、(18.680±0.081)%和(0.490±0.003)%。综合SPME-GC-MS、电子鼻和感官评价结果比较,1% NaCl (W/W)+1% Na2CO3(W/W)+4.0% C2H5OH (V/W)漂洗介质处理后,白鲢鱼糜的挥发性气味物质残留少,总含量降低为(6.57±0.77)μg/kg,17种气味活性物质的OAV<1,仅壬醛的OAV为1.34±0.05,可构建出低气味的鱼糜本底模型。
关键词白鲢    鱼糜气味本底模型    挥发性物质    固相微萃取/气质联用    气味活度值    电子鼻    
The Construction of a Low-Odor Background Model of Silver Carp (Hypophthalmichthys molitrix) Surimi
GENG Haiyong , CHEN Lihua , YANG Fang , WU Yi , WANG Shufen , JIANG Qixing , XU Yanshun , XIA Wenshui     
State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province, Jiangnan University, Wuxi 214122, China
Abstract: In the Healthy China Strategy context, fish are increasingly in demand as a source of high-quality protein. Silver carp (Hypophthalmichthys molitrix) is a resource-rich and highly productive freshwater fish species found in China that is not edible raw or cooked in its original form due to its many boney spines. However, due to its advantages of being low-cost, low in fat, and high in protein, it is an ideal choice for surimi production. Currently, it is widely used in the industrial production of surimi products. The development of the freshwater surimi industry can significantly improve the added value of freshwater fish utilization, which has attracted extensive attention. Freshwater surimi is high in protein and low in fat and has a smooth and delicate taste, making it extremely popular with consumers. It has a high output, low price, is growing in demand, and is gradually being accepted throughout domestic and foreign markets. It has also driven the development of some related industries and produced significant economic and social benefits. As domestic consumers experience improved living standards and a faster pace of work, premade dishes containing surimi products as well as recreational snack surimi products with increased shelf-life are more attractive, as they save the consumer processing time, are enjoyed by the consumer, and meet their nutritional demands, affording these products great market potential. With the development of surimi products and related industries, specific requirements are being put forward for its production. Although China supplanted Japan as the largest producer of surimi products worldwide in 2006, ushering in a period of nearly 10 years of high production growth, the annual production of surimi products in China since 2014 has stagnated or even slightly decreased. Moreover, the surimi industry has entered a bottleneck period for quality enhancement caused by the expansion of quantity. The fishy odor of freshwater surimi is one of the industrial problems that affect the quality and efficiency of surimi. The flavor of surimi products (such as fish balls, fish intestines, fish cakes, and others in hot pot) has become one of the quality attributes that consumers are extremely concerned about. However, the adsorption and release laws of key odor-active substances are still unclear. There are existing research technologies for surimi odor, mainly including instrumental analysis (gas chromatography-mass spectrum, gas chromatography-olfactometry, gas chromatography-olfactometry- mass spectrum, electronic nose technology, etc.), sensomics analysis (odor activity value (OAV), aroma extract dilution analysis, odor recombination, odor omission test, etc.), and enzyme-linked immunosorbent assay. The research objects of odor sensory experiments are mostly rice wine, oil, vegetables, fruits, and fungi. Moreover, present odor research is mainly carried out in a prepared solution, mainly using odor recombination of a liquid simulation system, which is different from the interaction between the real odor active substance-solid surimi. Therefore, constructing an odor model based on solid surimi is necessary to better simulate the sensory characteristics of surimi. To build an odor model based on solid surimi, an odorless or low-odor surimi background model must be established in order to investigate the interaction between various odor components and surimi. There are several fishy substances and complex components in freshwater fish and surimi products, including aldehydes, alcohols, ketones, esters, sulfur compounds, nitrogen compounds, and alkanes.At present, most studies on rinsing surimi reported worldwide are based on how to better apply it to the food system, ignoring interactions between components in the complex system of surimi, which creates certain limitations in establishing a background model of surimi. Therefore, salt, salt-alcohol, acid, alkali, and other rinsing media were selected in this study, which was not limited to food systems. By comparing the removal effects of different rinsing media on the odor residue of surimi, an odorless or low-odor background model of surimi could be constructed. Here, the effect of different rinsing media on the odor residue of a surimi background model was studied. Specific rinsing media were as follows: 0.5% NaCl (W/W) + 0.35% Na2CO3 (W/W) + 4.0% C2H5OH (W/W) solution (group A), 0.5% NaCl (W/W) + 0.35% Na2CO3 solution (group B), 0.5% CaCl2 (W/W) + 0.35% Na2CO3 (W/W) + 4.0% C2H5OH (V/W) solution (group C), 0.5% CaCl2 (W/W) + 0.35% Na2CO3 (W/W) solution (group D), 1% NaCl (W/W) + 1% Na2CO3 (W/W) + 4.0% C2H5OH (V/W) solution (group E), 1% NaCl (W/W) + 1% Na2CO3 (W/W) solution (group F), 1 mol/L HCl solution (group G), and 1 mol/L NaOH solution (group H), respectively. The results showed that SPME-GC-MS detected 65 volatile compounds in silver carp surimi, including 22 aldehydes, 13 alcohols, 9 ketones, and 7 hydrocarbons, among which the contents of aldehydes and alcohols were high, which had a major contribution to the odor of silver carp surimi. A total of 18 odor-active substances were detected by the OAV (≥1) method, which helped illustrate that odor-active compounds contribute to the overall odor of surimi. After treatment with eight kinds of rinsing media, the residual amount of the odor-active substances in the silver carp surimi was washed or released to varying degrees, affecting the sample's overall odor contribution. The rinsed surimi samples contained 6,8,7,9,6,12,9, and 9 odor active compounds and residual rates of volatile odor compounds were (0.380±0.120)%, (0.610±0.086)%, (0.280±0.033)%, (0.480±0.037)%, (0.150±0.018)%, (4.330±0.160)%, (18.680±0.081)%, and (0.490±0.003)%, respectively. According to the SPME-GC-MS analysis results, due to the synergistic effect of ethanol, the content of volatile compounds detected in group E was the lowest, the total residual amount of odor-active compounds was reduced to (6.57±0.77) μg/kg, and the total residue rate was only 0.15%. Meanwhile, the total OAV decreased to 2.52±0.25, there were 17 odor-active substances with an OAV<1, and the OAV of nonanal was only 1.34±0.05, which could establish a low-odor background model of surimi. Furthermore, electronic nose and sensory evaluations distinguished the overall odor characteristics between different rinsed samples and fresh surimi.This study took silver carp surimi as the research object and studied the influence of volatile odor compounds and salts, salt-alcohols, acids, alkalis, and other rinsing media in surimi on the residual rate of odor substances through SPME-GC-MS, electronic nose, and sensory evaluation methods, which will significantly contribute to the establishment of an odorless or low-odor solid surimi model and provide a novel idea for sensory analysis.
Key words: Silver carp    Background model of surimi odor    Volatile compounds    SPME-GC-MS    Odor activity value    E-nose    

我国渔业总产量已连续多年居世界首位,其中,淡水鱼的养殖产量占世界2/3以上,2021年我国淡水养殖产量达到3 183.27万t,相比2020年增长了3.06%(农业农村部渔业渔政管理局等, 2022)。白鲢鱼(Hypophthalmichthys molitrix)是我国淡水鱼中资源丰富、产量巨大的鱼类之一,但因其肉薄且骨刺较多、土霉味与鱼腥味较重且不易去除、不宜生鲜食用,并不十分受广大消费者的喜欢。另外,白鲢产量充足、成本低廉,具有低脂肪、高蛋白等优点,是制作鱼糜的经济性选择,目前已被广泛应用于工业化生产鱼糜制品(孙静文, 2016)。鱼糜制品如鱼丸、鱼肠、鱼糕等属于低脂肪、高蛋白的营养健康食品,深受消费者喜爱(唐淑玮等, 2019),且其风味是消费者关心的质量属性之一,而关键气味活性物质的吸附释放规律并不明确。现有对鱼糜气味研究技术十分丰富,主要为仪器分析法(气相色谱–质谱联用、气相色谱–嗅觉测定法、气相色谱–嗅闻–质谱联用、电子鼻技术等)、感官组学分析法(气味活度值、芳香提取物稀释分析、气味重组、气味遗漏实验等)和酶联免疫法(ELISA)等。目前,气味感官实验的研究对象大多为米酒类、油类、蔬果类、菌类等(Xu et al, 2019; Sun et al, 2021; 卢祺, 2022),且现有气味研究主要在配置溶液中进行,主要采用液体模拟体系的气味重组(An et al, 2020; 王国超等, 2012),这与真实的气味活性物质—固态鱼糜之间的相互作用存在一定差异,因此,基于固态鱼糜进行气味研究是十分必要的,可以更好地研究各气味成分与鱼糜无气味本底之间的互作关系。

如何基于固态鱼糜构建气味重组或缺失模型,首先要建立一个无气味或低气味的鱼糜本底模型。淡水鱼气味中有多种复杂成分,主要包括醛类、醇类、酮类、烃类和少量的呋喃类等(王国超等, 2012)。气味物质来源复杂,主要有养殖环境中存在的土臭素(GEO)和二甲基异莰醇(MIB)、酶的催化分解、游离脂肪酸的氧化分解等因素导致(吴燕燕等, 2016)。目前,鱼糜加工过程中减少气味残留的方法主要有物理法(感官掩蔽法、浸泡或漂洗法、吸附法、微胶囊法、包埋法、辐照法、电渗析法)、化学法(酸碱盐法、抗氧化剂法、有机溶剂萃取法、臭氧法)、生物法(酵母菌、乳酸菌、醋酸杆菌发酵)等(柳敏, 2015; 苏怡等, 2019; 杨运懿, 2021),其中,物理法是应用历史最久的方法,化学法在鱼糜制品的生产实践中有广泛的应用,生物法具有去除率高、环境友好、成本低等特点(Yuan et al, 2021)。然而,国内外报道中关于漂洗鱼糜的研究大多是基于如何更好地应用于食品体系,在漂洗试剂的选择上存在一定局限性,对腥味的洗脱能力受限,腥味成分残留仍较多,无法用于构建无腥味或低腥味鱼糜模型。因此,本研究选择盐、盐–醇、酸、碱等漂洗介质,并不限于食品体系,通过比较不同漂洗介质对鱼糜气味的脱除效果,以此构建出无气味或低气味的鱼糜本底模型。

固相微萃取(SPME)具有操作简单、灵敏度高、重现性好的优点,可以获得更真实的分析结果(Ma et al, 2013)。气相色谱–质谱(GC-MS)是分离和鉴定挥发性化合物的常用方法,已广泛应用于挥发性化合物分析(Iglesias et al, 2009)。电子鼻是一种分析、识别和检测简单和复杂气味的仪器。因其测定结果客观、重复性好、不损伤样品及快捷等特点,可以客观地判断不同样品间的挥发性气味是否具有差异性,被广泛地运用于水产品挥发性物质检测,为其气味和品质鉴定提供参考依据(杨欣怡等, 2015; 康翠翠等, 2018; 赵玲等, 2021)。本研究以白鲢鱼糜为研究对象,通过SPME-GC-MS、电子鼻以及感官评价方法研究鱼糜中挥发性风味物质和盐、盐–醇、酸、碱等漂洗介质对气味物质残留率的影响,对于建立无气味或低气味的固体鱼糜模型有一定的学术指导意义。

1 材料与方法 1.1 材料与试剂

鲜活白鲢鱼购自江苏省无锡市滨湖区欧尚超市,所选鱼体平均质量为(2.5±0.2) kg/尾,于2021年3月下旬至4月中旬采购;2,4,6-三甲基吡啶标准品(trimethyl pyridine, TMP)购于上海百灵威科技公司;NaCl、无水乙醇、Na2CO3、CaCl2、HCl和NaOH等化学试剂均为分析纯,购于国药集团化学试剂有限公司。

1.2 仪器与设备

MDF-U53V型超低温冰箱,日本三洋公司;多功能食品加工机,浙江温州福菱科技有限公司;4K15冷冻离心机,德国Sigma公司;T10 Basic ULTRA-TURRAX均质机,广州IKA仪器设备有限公司;卧式冷藏冷冻转换柜,山东青岛海尔电冰柜有限公司;TSQ 8000型三重四级杆气质联用仪(GC-MS),美国赛默飞世尔科技公司;Heracles II型快速气相色谱电子鼻,法国Alpha MOS S.A.公司。

1.3 实验方法 1.3.1 样品制备

新鲜白鲢鱼宰杀后去鳞、去头、去内脏、去除血块和黑色腹膜,然后清洗3~5次,从背部切成两半,去除椎骨,手工剥离鱼刺,以获得白肉。由斩拌机绞碎获得白鲢生鲜鱼糜,用聚乙烯自封袋包装,储存在冰箱(–20 ℃)中备用。

1.3.2 白鲢鱼糜的漂洗方法

鱼糜样品在4 ℃下解冻12 h,并用漂洗液处理。实验中所用的不同漂洗介质溶液见表 1。参照Zhou等(2016),漂洗介质A、B、C、D、E和F组的具体漂洗步骤如下:解冻后的鱼肉样品分别取相同质量,每个样品漂洗3次(5倍于鱼肉体积的漂洗液),每次漂洗时间为15 min,漂洗后进行冷冻离心脱水(4 ℃, 4 000 r/min, 4 min),以此得到漂洗鱼糜。

表 1 不同漂洗介质的组成 Tab.1 The components of different rinsing media

漂洗介质G组和H组的具体漂洗步骤如下:解冻后的鱼肉样品加入5倍体积的蒸馏水,用均质机缓慢搅拌,同时缓慢滴加几滴1 mol/L HCl或1 mol/L NaOH调整pH,pH分别调到预定值2.3 (G组)和11.8 (H组),再搅拌15 min;然后离心(4 ℃, 10 000 r/min, 20 min),去掉沉淀。调整上清液pH值到5.5,再次离心(4 ℃, 10 000 r/min, 20 min),下层沉淀即为所得漂洗鱼糜。

以上各介质均溶解在蒸馏水中,且它们的使用浓度均经预实验优化过。考虑到乙醇具有很强的挥发性,大量的乙醇在SPME提取时可能会吸附到萃取头,影响其他挥发性成分的吸附。因此,在冲洗的最后步骤,漂洗液与鱼糜通过离心分离,并用清水清洗一次,确保各漂洗介质在鱼糜中无残留。样品封装于铝箔袋中,于–80 ℃超低温冰箱中贮存待测。整个过程均在0~10 ℃下操作。

1.3.3 GC-MS测定挥发性成分的条件

固相微萃取法(SPME)条件:样品在提取前按照Gao等(2016)的方法制备,并进行了一些修改。将3.0 g样品放入20 mL的棕色顶空瓶中,加入7 mL饱和NaCl溶液和2,4,6-三甲基吡啶(2,4,6-trimethyl pyridine, TMP, 100 mg/kg),并放入磁力转子,迅速加盖。纤维萃取头(65 μm,PDMS/DVB)插入样品瓶的顶空,在60 ℃吸附30 min后,在250 ℃的注入口解吸3 min。

气相色谱(GC)条件(Gao et al, 2020):使用TG-5毛细管柱(60.00 m × 0.25 mm × 0.25 μm);载气为He,恒定流量1.0 mL/min。升温程序:初始温度40 ℃;初始时间3 min;进样口温度280 ℃;柱温40 ℃,保持2 min,以5 ℃/min升至90 ℃,保持5 min;不分流模式进样。

质谱(MS)条件:使用EI离子源,离子源温度300 ℃,发射电流25 μA;电子能量70 eV;质量扫描范围设定35~350 m/z;接口温度280 ℃;探测器电压1 000 V。

1.3.4 定性和定量分析

定性:挥发性化合物根据系统自带的NIST 2008和Willey 7标准图库以及文献报道的色谱数据进行定性匹配,且仅当正反匹配度均大于800 (最大值为1 000)的化合物才予以报道。同时,以C7~C40的正构烷烃作为标准品,利用标准品的保留时间计算出各个样品中化合物的保留指数,和文献中的保留指数进行对比,结合数据库的分析结果,共同对萃取出的挥发性化合物进行定性分析(康翠翠等, 2018)。

定量:将10 μL原始质量分数为100 mg/kg的内标物2,4,6-三甲基吡啶(TMP)加入(3.000±0.006) g鱼糜样品中,通过将各化合物的峰面积与TMP的峰面积进行比较,计算出样品中挥发性化合物的浓度,单位为μg/kg (假定各挥发物的绝对校正因子为1.0)。计算公式如下:

$ 挥发性组分的质量分数=[(A_{x}×A_{T}^{–1})×m_{T}]×m_{x}^{–1}×10^{3} $

式中,AxAT分别为挥发性组分x与TMP的峰面积,mT是加入的TMP的质量(μg),mx是被测样品的质量(g)(Gu et al, 2013)。

1.3.5 关键气味化合物的确定


$\mathrm{OAV}_x=C_x / \mathrm{OT}_x$

式中,OAVx表示各风味物质的气味活度值,Cx表示各化合物的浓度,OTx表示各化合物在水中的检测阈值,其中,OAV≥1的化合物可定义为气味活性化合物(Xu et al, 2021)。

1.3.6 挥发物残留率的计算方法


$ R = C_{x}/C_{o} × 100\% $

式中,CxCo分别为实验组和对照组漂洗后组分x检测出的质量分数(μg/kg) (张建友等, 2015)。

1.3.7 电子鼻分析

参考Wen等(2020)的方法并稍加修改,分别准确称取2.0 g前处理好的鱼糜样品置于20 mL顶空瓶中,样品气味比较通过HeraclesⅡ电子鼻进行分析(包含DB-5和DB-1701柱子,10.00 m× 0.25 mm×0.25 μm,Agilent),采用自动顶空进样,每个样品重复3次测定。检测条件如下:在40 ℃下保温30 min,FID检测器温度为250 ℃,氢火焰离子化检测器温度260 ℃;捕集温度50 ℃;阀门温度250 ℃;进样口温度200 ℃;进样量3 000 μL;进样速度125 μL/s。柱温从起始柱温50 ℃以2 ℃/min逐渐升至250 ℃。

1.3.8 感官评价

鱼糜样品的感官特性由10名小组成员(2男8女)以5分制进行评估(5分,非常强;4分,强;3分,中等;2分,弱;1分,非常弱)(An et al, 2020)。选取脂肪味、鱼腥味、青草味、泥土味、蘑菇味和金属味6种气味属性作为感官评价指标,来评估样品的强度,结果绘制在雷达图中。所有测试均在室温(22±2) ℃下进行,每个取样一式3份进行。

1.4 数据处理

所有实验重复3次,定量结果用“平均值±标准差”(Mean±SD)表示。通过Excel 2019进行数据处理;SPSS 19.0中的Duncan多范围检验评估平均差异方法(P<0.05)进行显著性分析;Origin 2019b进行绘图。

2 结果与讨论 2.1 白鲢生鲜鱼糜挥发性成分鉴定

经SPME-GC-MS检测分析,白鲢鱼糜中具体挥发性物质组成及含量如附表1所示。经NIST谱库检索,白鲢鱼糜中共确定65种挥发性物质,其成分主要有醛类(23种)、醇类(13种)、酮类(10种)、烷烃类(7种)和其他类物质(12种),各类物质的相对百分含量分别为37.78%、24.34%、8.83%、2.90%和9.14%,其中,醛类和醇类物质百分含量最高,对鱼糜的气味起主要作用,这与文献中已报道的白鲢鱼糜气味组成成分基本相符(An et al, 2020; Zhou et al, 2016; Geng et al, 2022)。经仪器检测的这些气味物质成分中,醛类中戊醛、己醛、庚醛、辛醛、壬醛含量较高,分别占总含量的1.76%、21.10%、3.22%、2.84%和4.94%;醇类中正戊醇、正己醇、庚醇、1-辛烯-3-醇、辛醇含量较高,分别占总含量的1.31%、6.00%、2.02%、8.31%和3.4%;酮类中2-庚酮、2,5-辛二酮含量较高,分别占总含量的1.10%和5.21%;烃类化合物中3,5,5-三甲基-2-己烯含量较高,占总含量的1.15%;其他化合物中氨基甲酸、2-乙基呋喃、八甲基环四硅氧烷含量较高,分别占总含量的1.92%、1.54%和3.10%,其中,八甲基环四硅氧烷可能是萃取头涂层上的物质脱落而致。有18种物质的气味活度值OAV≥1,如附表1所示,分别是戊醛、己醛、庚醛、辛醛、(E)-2-辛烯醛、壬醛、(E)-2-壬烯醛、癸醛、(E)-2-癸烯醛、十一醛、正己醇、庚醇、1-辛烯-3-醇、辛醇、1-壬醇、2-乙基呋喃、2-戊基呋喃和乙酸乙酯。

2.2 不同漂洗介质对白鲢鱼糜挥发性物质的影响

白鲢鱼糜中气味物质组成复杂,部分气味物质会与蛋白质等大分子物质结合的形式存在(蒋娅婷等, 2014)。采用不同漂洗介质处理,不仅可以通过直接漂洗达到脱脂脱腥的目的,还可以通过破坏气味物质与蛋白等大分子物质之间的结合作用力而达到降低气味残留量的目的(柳敏, 2015)。不同漂洗工艺对白鲢鱼糜挥发性物质的影响如表 2所示。经8种漂洗介质处理后,鱼糜中挥发性物质均有明显减少,样品中分别含有6、8、7、9、6、12、9和9种气味活性物质,挥发性气味物质的残留量依次为16.53±5.11、26.72± 3.73、12.08±1.42、21.03±1.59、6.57±0.77、188.68±6.77、812.68±3.54和(21.27±0.12) μg/kg,其气味残留率分别为(0.380±0.120)%、(0.610±0.086)%、(0.280±0.033)%、(0.480±0.037)%、(0.150±0.018)%、(4.330±0.160)%、(18.680±0.081)%和(0.490±0.003)%,其中,漂洗液A、B、C、D、E和H组这6组漂洗方式对白鲢鱼糜处理后,对醛类物质中的戊醛、己醛、庚醛、辛醛、壬醛和醇类物质中的正己醇、庚醇、1-辛烯-3-醇、辛醇等有明显影响,均大大降低了气味残留率。但漂洗液F组对醛类物质中的己醛气味残留量高达(145.53±4.88) μg/kg,漂洗液G组对醛类物质中的戊醛、己醛、庚醛、壬醛和醇类物质中的正己醇、1-辛烯-3-醇起不到良好的去除作用,原因可能是溶液浓度过高,可能导致部分鱼糜中的蛋白质变性,造成蛋白网络结构的物理阻碍,从而产生更多的挥发性物质。比较8种漂洗介质,发现漂洗液E组对鱼糜气味残留的影响较佳,挥发性物质总含量最低,其中,漂洗后己醛和1-辛烯-3-醇的残留量分别为2.93±0.32和(0.26±0.09) μg/kg,各自的气味残留率仅为0.18%和0.04%。

表 2 不同漂洗介质处理后气味活性物质的残留量 Tab.2 Residual amount of odour active substances after treatment with different rinsing media(ug/kg)

NaCl和Na2CO3是常用的漂洗介质,NaCl和Na2CO3共存的状态下,水产品中气味成分先与Na2CO3发生反应生成无腥味的物质,后者进一步在NaCl的作用下从水产品中析出(柳敏, 2015)。Na+和Ca2+等离子的存在能溶出鱼糜中的血红蛋白,蛋白质损失增加,削弱了与挥发性气味物质的结合能力,进而促使溶液中挥发性物质的释放。Na2CO3可与气味成分反应生成无腥味的物质,也可将容易降解成醛酮类物质的油脂水解成能溶于水的高级脂肪酸钠盐和甘油(游丽君等, 2008),从而达到降低气味残留率的目的。图 1显示了不同漂洗介质对18种气味活性物质OAV减少量的影响。OAV变化可以表明不同的漂洗介质可能会导致样品的整体气味分布发生显著变化(Zhou et al, 2016)。结合表 2图 1可知,在8组漂洗介质中,18种气味活性物质的OAV总值分别降低为7.66±2.56、11.02±2.62、4.80±0.99、9.93±0.68、2.52±0.25、50.27±1.61、283.22±1.60和8.77±0.04,其中,漂洗液E组对OAV的影响最明显;(E)-2-辛烯醛、(E)-2-壬烯醛、癸醛、(E)-2-癸烯醛、十一醛和2-戊基呋喃等6种气味活性物质均未检出气味残留量,其OAV减少率达到最大;己醛、辛醛、壬醛和1-辛烯-3-醇的OAV下降幅度较大,其OAV减少量均在200以上。综上所述,漂洗液E组在加入4.0%乙醇(V/W)溶液后,有17种气味活性物质的OAV<1,仅壬醛的OAV为1.34±0.05,这对降低鱼糜气味残留起到了很好的协同增效作用。乙醇的加入,由于相似相容原理,有利于鱼糜脂质的酯化,加快了气味成分的溶出;同时使鱼糜表面脱水,通过溶质浓缩效应造成蛋白质变性,从而破坏挥发性气味物质与蛋白质等大分子物质之间的结合作用力,而高浓度的NaCl加速蛋白变性,促进溶液中挥发性物质的释放,大大降低了气味物质中醛类和醇类的残留率,从而可构建出低气味的鱼糜本底模型。

图 1 不同漂洗介质对气味活性物质OAV的影响 Fig.1 Effects of different rinsing media on OAV of odor active substances A、B、C、D、E、F、G和H依次为漂洗介质A、B、C、D、E、F、G和H处理后的鱼糜样品。下同。 A, B, C, D, E, F, G and H were the surimi samples treated with rinsing medium A, B, C, D, E, F, G and H, respectively. The same below.
2.3 电子鼻分析

主成分分析法(principal component analysis, PCA)是将传感器提取的原多维矩阵数列通过降维、数据处理和线性分类转换为互不相关的几个综合指标的方法(郑舒文等, 2019)。PCA作为一种常用的降维分析方法,能够将不同样品按照主成分划分在不同的区域,区域之间的距离表示不同样品之间的差异(吴丹等, 2022)。电子鼻响应数据的PCA分析结果如图 2a所示。PCA图由2个轴PC1和PC2组成,其中,PC1的方差贡献率为99.993 0%,PC2的方差贡献率为0.004 5%,2组总贡献率为99.997 5%,表明PC1和PC2 2个主要成分可以代表几种被测试样品的整体气味特征。从图 2a中可以看出,A组和E组样品与新鲜鱼糜样品在PC1的距离远大于其他样品,在气味上有部分相似,表明漂洗介质A组和E组的漂洗效果更为明显。判别因子分析法(discriminant factor analysis, DFA)是用少数几个因子来描述多个因素之间的联系与差异,通过DFA分析可以使样品组间距离最大的同时保证组内差异最小,进行定性判别,对样品间的差异较PCA有更好的区分度(吴丹等, 2022)。根据DFA分析结果,DF1和DF2方差贡献率分别为85.714%和9.493%。95.207%的总体方差贡献率,表明DFA分析能有效区别各组样品的气味差异。根据图 2b可知,A组和E组与新鲜鱼糜样品距离较远。电子鼻分析结果与GC-MS分析结果基本一致,进一步证实A组和E组的漂洗处理都能有效降低鱼糜的气味残留量。

图 2 不同鱼糜样本电子鼻响应数据的PCA(a)和DFA(b) Fig.2 PCA (a) and DFA (b) of e-nose response data for different surimi samples Control:新鲜鱼糜。下同。 Control: Fresh surimi. The same below.
2.4 感官评价

不同鱼糜样品漂洗前后的气味感官雷达图如图 3所示。与新鲜白鲢鱼糜样品的感官评分相比,8种漂洗介质处理后的样品都影响了鱼糜的气味感官轮廓,在一定程度上都降低了各个气味属性的评分,尤其是漂洗介质A、B、C、D和E组漂洗处理后,对“鱼腥味”、“脂肪味”、“泥土味”、“青草味”、“蘑菇味”和“金属味”等6种气味属性均有显著影响,这与GC-MS和电子鼻的分析结果基本一致。然而,该感官评价实验并不能够很好地区分漂洗后的不同鱼糜样品,尤其是对于A、B、C、D和E组漂洗介质,它们各气味属性得到的感官评分值基本在同一水平位置,在雷达图(图 3)中的感官轮廓很难区分开来。其中,E组漂洗处理后对各气味属性的影响较为明显,6种气味属性的感官评分值基本为0,说明漂洗后的样品已经达到了低气味的水平,符合低气味固体鱼糜模型的构建标准。

图 3 不同鱼糜样品的气味感官雷达图 Fig.3 Odor sensory radar chart of different surimi samples
3 结论

经SPME-GC-MS分析,在白鲢鱼糜中共检出65种挥发性物质,主要包括醛类22种、醇类13种、酮类9种及烃类7种等,其中,醛类和醇类物质含量较高,对白鲢鱼糜的气味有主要的贡献作用。采用气味活度值法(OAV≥1),共鉴定出18种气味活性物质,这有助于说明气味活性物质贡献了鱼糜整体气味。由GC-MS分析结果可知,8种漂洗介质在不同程度上洗去或释放了白鲢鱼糜中气味活性物质的残留量,从而影响了样品的整体气味贡献。相较于其他漂洗介质,漂洗介质E组由于乙醇的协同作用,检出的挥发性物质最少,气味活性物质的总残留量为(6.57±0.77) μg/kg,总残留率仅为0.154%,OAV总值降低至2.52±0.25,对气味物质的去除效果最佳。同时,电子鼻检测和感官评价也区分了不同漂洗样品和新鲜鱼糜之间的整体气味特征差异。该研究对于建立低气味的固体鱼糜模型有一定的学术指导意义,为感官组学分析提供了一种新思路。

表 附表1 白鲢鱼糜的挥发性成分物质组成及含量 Tab.附表1 Composition and content of volatile components in silver carp surimi
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