辐照对猪肉火腿肠风味与品质的影响

分别以1、3、5、7、9 kGy剂量辐照处理火腿肠,然后对其辐照异味强度、脂质氧化、挥发性风味化合物、色差等指标进行检测,分析辐照对火腿肠风味及颜色品质的影响。结果发现,辐照处理可以显著促进火腿肠中脂质的氧化(P0.05),使得红度值(a~*)相比对照组显著降低(P0.05),但是对亮度值(L~*)和黄度值(b~*)影响不显著(P0.05)。随着辐照剂量加大,火腿肠的辐照异味明显增强,1~5 kGy范围内辐照异味不明显,当辐照剂量增加到7 k Gy时,火腿肠产生明显的令消费者不能接受的辐照异味。挥发性含硫化合物、2-丁烯、戊烷、1-戊烯、辛烷、己烷以及醛类化合物含量与对照组相比显著增多(P0.05),且与辐照剂量呈正相关。二硫化碳、二甲基二硫醚、2-甲基丙醛、3-甲基丁醛、己醛、丁烯和二甲苯是火腿肠辐照后产生的最主要挥发性化合物。结果表明,火腿肠经辐照处理后风味和色泽会发生劣变,特别是5 kGy以上的辐照剂量,并且这些品质变化与火腿肠中脂质的氧化密切相关。     

不同复水条件对香菇特征香味物质的影响

目的研究干香菇经不同复水条件处理后其特征香味物质含量的变化,实现干香菇的科学复水。方法新鲜香菇经热风干燥后进行复水处理,通过顶空固相微萃取-气相色谱-质谱联用(headspacesolid-phase microextraction-gaschromatography-massspectrometry,SPME-GC-MS)的方法对复水香菇中的挥发性含硫化合物和八碳化合物进行分析,以环己酮为内标物,采用内标法进行定量分析,分别考察不同复水时间、不同复水温度和不同复水pH值下香菇中特征香味物质的含量。结果经不同复水时间处理后,香菇中含硫化合物含量为38.30～79.84μg/g,八碳化合物含量为4.33～10.97μg/g;经不同复水温度处理后,香菇中含硫化合物含量为12.82～44.45μg/g,八碳化合物含量为2.50～9.84μg/g;不同pH值条件下复水处理后,香菇中含硫化合物含量为6.10～72.52μg/g,八碳化合物含量为0.86～7.61μg/g。结论结果表明,干香菇在温度为40℃、pH值为9时,复水处理40min,其挥发性含硫化合物的含量较高,复水香菇表现为浓郁的"香菇味";干香菇在温度为40℃、pH值为7时,复水处理20 min,其挥发性八碳化合物的含量较高,复水香菇表现为明显的"蘑菇味",应根据实际情况选择合适的复水条件。     

不同剂量辐照对鸡胸肉挥发性化合物的影响

为探究电子束辐照对鸡胸肉异味产生的影响，对不同剂量辐照鸡胸肉中的挥发性化合物进行检测和分析。用固相微萃取-气相色谱-质谱联用法(solid phase microextraction-gas chromatography-mass spectrometry, SPME-GC-MS)对不同剂量辐照鸡胸肉中的挥发性化合物进行分析，对辐照鸡胸肉进行感官评价实验，结合挥发性化合物含量进行偏最小二乘回归分析(partial least squares regression, PLSR)。检测到了18种香气活力值(odor activity value, OAV)大于1的挥发性化合物，其中2 kGy剂量辐照对鸡胸肉中挥发性化合物影响最明显。确定了对鸡胸肉果香、霉香、油脂、鸡肉味、油漆味有重要贡献的特征化合物。感官评价得分结合挥发性化合物的OAV表明反-2-辛烯醛、1-辛烯-3-醇、壬醛、3-羟基-2-丁酮可能是辐照鸡胸肉产生辐照异味的特征化合物。实验结果为电子束辐照食品中异味的检测及掩盖提供理论依据，推动电子束辐照保鲜技术在其他食品中的应用。     

60Co-γ辐照对美味牛肝菌挥发性成分的影响

为研究60Co-γ辐照对美味牛肝菌挥发性成分的作用,对其干品进行1.29和3.38 kGy的60Co-γ辐照处理,并采用顶空-固相微萃取技术结合气质联用仪对其挥发性成分进行鉴定。结果表明,辐照前后的美味牛肝菌干品中共鉴定出43种挥发性成分,包括7种吡嗪类,4种烃类,1种醛类,1种酮类,5种酚类,2种酯类,8种酸类,11种杂环类和4种未知化合物。其中酸类、吡嗪类、烃类和杂环类化合物相对含量最高,分别为28.43%、18.11%、17.41%和17.25%。美味牛肝菌干品中还鉴定出23种与食用菌风味产生密切相关的含八碳及以下的挥发性化合物,总体相对含量达48.16%。1.29、3.38 kGy两种剂量的辐照处理显著降低了美味牛肝菌中大部分风味相关的挥发性成分的相对含量(p<0.05),吡嗪类、杂环类和八碳及以下挥发性化合物的相对含量分别下降14.36%和17.28%、14.49%和17.27%以及11.27%和11.75%;而酸类成分相对含量则增加了9.18%和45.55%。本研究结果可为辐照处理在美味牛肝菌保藏中的应用提供了试验数据。     

大蒜挥发性成分顶空取样与固相微萃取GC-MS分析

为了探索大蒜挥发性成分分析前处理方法,以新鲜大蒜和市售的糖醋蒜为材料,分别采用顶空取样和固相微萃取提取其挥发性成分,并进行GC-MS分析,结果表明:不同采集方法检出的挥发性成分和含量有所不同,顶空取样检测出新鲜大蒜和糖醋蒜的挥发性成分种类和相对含量以及含硫化合物相对含量都较高;两种方法分别检出新鲜大蒜和糖醋蒜的共有含硫化合物分别为11种和6种。相对固相微萃取,顶空取样操作简单,快速,可用于大蒜及其加工品挥发性成分的测定。     

大蒜挥发性成分静态顶空取样GC-MS分析条件的筛选

为了筛选静态顶空取样GC-MS分析大蒜挥发性成分的适宜条件,以新鲜大蒜鳞茎为试料,对样品量、平衡温度和平衡时间等不同分析条件下大蒜挥发性成分种类、含硫化合物种类和含硫化合物相对含量的变化进行了分析比较研究.结果表明:样品量7 g,在40℃下平衡30 rmin是静态顶空取样分析大蒜挥发性成分的适宜条件;在此条件下,检测到大蒜挥发性成分24种,其中含硫化合物18种,含硫化合物相对含量99.o2％,且大蒜的主要功能成分都有检出.     

烫漂方式对香菇挥发性成分的影响

比较微波、蒸汽和沸水烫漂对香菇挥发性成分的影响。采用顶空固相微萃取-气相色谱质谱联用技术进行挥发性成分定性分析,并对苯甲醛与1-辛烯-3-醇进行外标法定量分析。结果表明:新鲜香菇的主要挥发性化合物分为五类25种,包括醇类6种、醛类4种、酮类2种、烃类5种和含硫化合物8种,苯甲醛与1-辛烯-3-醇分别为0.28 ng/g和308.44 ng/g。微波烫漂的香菇中1-辛烯-3-醇含量为515.65 ng/g;蒸汽烫漂与沸水烫漂对醇类与含硫化合物的相对含量影响较大,其中蒸汽烫漂使香菇中醇类相对含量由22.49%降至3.93%,含硫化合物相对含量由64.57%增至87.64%,苯甲醛与1-辛烯-3-醇含量分别为0.45 ng/g和245.64 ng/g;香菇经沸水烫漂,醇类相对含量达87.89%,含硫化合物(2.85%)显著降低,1-辛烯-3-醇含量为1482.46 ng/g。以上表明,从挥发性成分组成来看,蒸汽烫漂与沸水烫漂处理对其差异影响较大,特别是醇类与含硫化合物的相对含量有明显区别。     

6类常见食品中含硫化合物风味特征及形成机理研究进展

挥发性含硫化合物广泛存在于多种食品中,具有阈值极低的特点,是对食品感官品质有重要贡献的特征风味组分,在形成食品独特风味特征中也起着至关重要的作用。不同种类的含硫化合物表现出的食品风味特征不尽相同,不同含量的含硫化合物对食品感官品质的影响也差异显著,因此,对感官风味受含硫化合物影响较大的6类常见食品中含硫化合物风味特征及其形成机理进行了研究。牛奶中主要含硫化合物是甲硫醇和二甲基三硫醚,通常表现为蒸煮味;2-甲基-3-呋喃硫醇是牛肉的关键含硫化合物,呈现为焙烤香和肉香;糠硫醇的焙烤香、3-巯基己烷-1-醇的果香是酒类中的关键风味组分;1,2,3,5,6-五硫杂环庚烷是呈现香菇独特气味的关键化合物;二丙基二硫醚、二甲基三硫醚和大蒜素分别为大葱、洋葱和大蒜风味形成的关键含硫化合物;二甲基硫醚和二甲基三硫醚是菜籽油呈现辛辣刺激风味的主要原因。含硫化合物主要是由含硫前体物质在微生物或酶的降解作用下形成,同时有些含硫化合物也产生于美拉德反应。通过对6类常见食品中含硫化合物的种类、对食品感官品质的影响及其形成机制进行全面介绍,总结常见食品中含硫化合物的风味及其对食品感官品质影响的一般规律,旨在为食品中含硫化合物形成机理及风味特征的进一步研究提供参考。     

顶空固相微萃取与气质联用法分析酵母浸膏辐照挥发性成分

采用顶空固相微萃取-气相色谱-质谱联用法分析酵母浸膏辐照后的挥发成分。结果表明：未经辐照的酵母浸膏萃取得到13 种挥发性成分,其中含酸类1 种、醛类2 种、醇类2 种、烯烃类1 种、含氮化合物3 种,主要成分为乙酸、吲哚、2-乙基己醇。辐照后的酵母浸膏萃取得到35 种挥发性成分,其中酸类1 种、醛类7 种、醇类2 种、烯烃类4 种、酮类2 种、含氮化合物14 种、含硫化合物2 种、酯类1 种、苯类2 种。挥发物的种类和含量均随辐照剂量的增加而增加。     

顶空固相微萃取-气相色谱-质谱联用法分析酵母浸膏辐照挥发性成分

采用顶空固相微萃取-气相色谱-质谱联用法分析酵母浸膏辐照后的挥发成分。结果表明:未经辐照的酵母浸膏萃取得到13种挥发性成分,其中含酸类1种、醛类2种、醇类2种、烯烃类1种、含氮化合物3种,主要成分为乙酸、吲哚、2-乙基己醇。辐照后的酵母浸膏萃取得到35种挥发性成分,其中酸类1种、醛类7种、醇类2种、烯烃类4种、酮类2种、含氮化合物14种、含硫化合物2种、酯类1种、苯类2种。挥发物的种类和含量均随辐照剂量的增加而增加。     

顶空固相微萃取结合气相色谱-质谱联用法对3种洋葱挥发性风味成分的分析

为研究洋葱挥发性成分,利用顶空固相微萃取法提取洋葱的挥发性风味成分,通过气相色谱-质谱联用法分析测定,以总峰面积和化合物个数为指标考察萃取纤维头、萃取温度、萃取时间和解吸时间4个因素对萃取效果的影响,得出最优萃取条件为:萃取纤维头50/30 μm DVB/CAR/PDMS,萃取温度60 ℃,萃取时间60 min,解吸时间5 min。利用最优萃取条件对三种色泽洋葱挥发性风味成分进行分析鉴定。结果表明:三种色泽洋葱共鉴定得到挥发性风味物质61种,其中白皮、红皮、黄皮洋葱分别测到37、40、49种挥发性成分,相对含量分别占流出组分总量的70.29%、81.92%、79.03%。61种挥发性成分中含硫化合物27种、醛类13种、醇类13种、酮类4种,其他4种。三种色泽洋葱的共有挥发性成分有22种,其中含硫化合物占比较大,特别是二异丙基二硫醚和(E)-1-丙烯基-2-丙烯基二硫醚相对含量的总和在三种色泽洋葱的挥发性成分中占比率都超过了20%,对形成洋葱特征风味贡献较大。红皮和黄皮洋葱的含硫化合物的相对含量远高于白皮洋葱,红皮洋葱中2-甲基-2-戊烯醛相对含量高于白皮和黄皮洋葱。     

同时蒸馏萃取和固相微萃取与气相色谱-质谱法分析洋葱的挥发性风味成分

羊葱是百合科葱属的一种世界性的蔬菜,具有很高的营养价值和药用价值。洋葱的多种含硫化合物使其具有特殊的辛辣气味。本文采用传统的同时蒸馏装置和固相微萃取技术结合气相色谱-质谱分析了洋葱的挥发性风味成分。通过对固相微萃取的纤维头、萃取时间和解吸时间的选择来优化其实验条件。共鉴定出52种成分,其中硫醇类、硫醚类是洋葱挥发性风味成分的主要贡献物质。     

Biochemical Studies on Some Chemical Characteristics of Sliced Egyptian Onions

Biochemical studies were carried out on two widely distributed Egyptian onion varieties (Behairy and Selected Giza 6). Several treatments (soaking in tap water, boiling water, cold water, warm ethanol, or sodium chloride solution) were proposed to overcome onion reddening during industrial processing. Some chemical characteristics (L-ascorbic acid, free amino acids, volatile sulfur compounds, carbonyl compounds, pungency and color) were determined in fresh, treated and stored sliced onions. Unsaturated fatty acids can be considered as a secondary source for carbonyl compounds and are involved in the formation of red pigments. Pronounced changes among hydrocarbons and little changes in sterols were due to application of various treatments and storage. In general, the most efficient treatments towards keeping onion quality were soaking the sliced onions in cold water or 5% (w/v) sodium chloride for 24 hr before onion dehydration.     

Investigation on the volatile oil of Makó onions

The authors have developed a method for determining the volatile oil content of onions. Using this method they found in the Hungarian Makó onions 0.019—0.031 % volatile oil, depending on storage. The composition of onion oil was studied by GC; GC-MS and TLC methods. GC-MS revealed 20 volatile sulphur compounds identified as 10 trisulphides, 6 disulphides, 3 tetrasulphides, and 1 thiophene derivative as well as one unsaturated aldehyde. Three of these: ethyl cis-1-propenyl trisulphide, ethyl trans-1-propenyl trisulphide, and butyl methyl trisulphide were described for the first time in onions. Carbonyl compounds were studied in the form of derivatives obtained with 2,4-dinitrophenyl hydrazine. On the basis of Rf-values and by addition, propanal, butanal, pentanal and hexanal were identified in the aldehyde fraction, while in the dicarbonyl fraction — beside an unknown compound — glyoxal and methyl glyoxal were identified. The presence of these two compounds in onion oil has been reported for the first time.     

洋葱黄酮类化合物的水提工艺条件研究

采用水浸提法提取洋葱中的黄酮类化合物,用比色法测定洋葱中黄酮类化合物的含量,并对黄酮类化合物提取过程中各因素对收率的影响情况作了研究,其影响的主次顺序为料液比>浸提温度>浸提时间。     

Identification of Thiols in Yellow Onion (Allium cepa L.) Using Solvent Vented Large Volume Injection GC‐MS

Thiols are often highly odor active molecules and as such can significantly contribute to aroma while being present at extremely low concentrations. This paper details the identification of thiols in yellow onion juice by solvent extraction followed by thiol enrichment using a mercuric agarose gel column. Due to the inherent thermal instability and low concentrations of thiols in onion, chromatographic analysis utilized larger volume solvent elimination injections. New sulfur compounds in onion included 1,1‐propanedithiol, bis‐(1‐sulfanylpropyl)‐sulfide, 1‐methylsulfanyl‐1‐propanethiol, 1‐propylsulfanyl‐1‐propanethiol, and 1‐allylsulfanyl‐1‐propanethiol. A discussion on the potential route of formation for each compound is included along with the orthonasal and retronasal evaluations of the synthesized molecules. This work investigated and identified 5 newly identified compounds present in onions that can impart onion character at low concentrations levels.     

Effects of cultivar,lifting time and nitrogen fertiliser level on quercetin content in onion (Allium cepa L.) at lifting

Commercial cultivars of onion (Allium cepa L.) were grown at Torslunda research station, Sweden with different levels of nitrogen fertiliser and lifted at different growth stages. Soon after lifting, before any drying or curing, tissue from the fleshy edible part of onions was extracted in ethanol and the raw extracts were analysed by high‐performance liquid chromatography without any previous hydrolysis. It was confirmed that the main flavonoid compounds were quercetin monoglucoside and quercetin diglucoside, whereas only trace amounts of quercetin aglycone and other flavonoids were found. The greatest variation in quercetin content, in the range 100–500 mg kg^?1 fresh weight, occurred between years. The concentration of quercetin glucosides in the onions was strongly correlated (R² = 0.98) with the total amount of global radiation in August. Individual onions with fallen leaves had significantly higher concentrations of quercetin glucosides than individuals in the same row with erect leaves. Only minor differences were found between the three cultivars analysed. Higher levels of nitrogen fertiliser had only minor effects on onion yield and size and resulted in lower or equal amounts of quercetin glucosides. Nitrogen leakage from the soil, a potential source of environmental problems, could therefore be minimised by avoiding high nitrogen fertiliser levels with almost no effect on onion flavonol content. Late lifting of onions (80% fallen leaves) resulted in up to 45% higher concentrations of quercetin glucosides compared with early lifting (50% fallen leaves). Copyright © 2006 Society of Chemical Industry     

Detection of onion postharvest diseases by analyses of headspace volatiles using a gas sensor array and GC-MS

Onion postharvest diseases cause significant losses in storage. Volatile sensing by the gas sensor array technology could be used as a promising alternative method to detect onion diseases. Onions were inoculated with Botrytis allii and Burkholderia cepacia, causal pathogen for Botrytis neck rot and sour skin, respectively. In the first phase of this study, 30 onions with equal number of B. allii inoculated and control healthy onions were measured by the gas sensor array from 8 to 11 days after inoculation (dai) and the principal component analysis (PCA) score plot demonstrated that the gas sensor array responded differently to Botrytis neck rot infected onions from those of healthy onions. In the second phase, 30 onions with 10 for each of the three treatments (Botrytis neck rot, sour skin, control) were measured by the gas sensor array on 5, 6, and 7 dai. The PCA score plot illustrated that three treatments formed three distinct clusters, while a hierarchical cluster analysis dendrogram indicated that the response of the gas sensor array to Botrytis neck rot and sour skin were similar. The correct classification rate of the linear discriminant model for three treatments was over 97.8%. Results from GC-MS showed that total 24 major volatiles were identified from the headspace of three treatments. Sixteen compounds were uniquely present in B. allii and B. cepacia inoculated onion bulbs. Total amount of volatile compounds detected in pathogen inoculated bulbs was one to two orders of magnitude higher than that of control healthy bulbs. This study demonstrated the feasibility of using a gas sensor array to detect two onion postharvest diseases in storage.     

Free Radical Scavenging and Leukemia Cell Growth Inhibitory Properties of Onion Powders Treated by Different Heating Processes

ABSTRACT: Methanol extracts of onion powder dried by hot air (60 °C), vacuum (35 °C), and lyophilization (35 °C) were used to study the effects of drying method on the quercetin composition and the subsequent antioxi-dative changes. It was found that hot air-dried onion had higher radical scavenging activities in both DPPH and peroxide radicals than those of the freeze- and vacuum-dried onions. HPLC analyses showed that freeze- and vacuum-dried onions contained more quercetin glycosides, whereas hot air-dried onion dominated in aglycone. A strong cell proliferation inhibition activity in hot air-dried onion was observed for leukemia cell lines CEM and U937, whereas freeze- and vacuum-dried onions gave comparatively moderate inhibition. Low cell proliferation inhibition was obtained in 3 dried onions for leukemia cell lines K562, P3HR-1, and Raji.     

Amount of characteristic compounds in 15 cultivars of onion (Allium cepa L.) in controlled field trials

BACKGROUND: In order to develop the production of sweet onions (Allium cepa L.) and onions with a high content of flavonols and fibre in Norway, it was necessary to evaluate available cultivars with respect to their content of selected chemical compounds. A field trial with 15 different cultivars was conducted at Landvik in southern Norway. Compounds that reflect onion pungency and sweetness (pyruvate, sugars) and parameters known to have a beneficial impact on health (fructo‐oligosaccharides (FOS), flavonols, antioxidant capacity) were analysed. RESULTS: The sweetest onions with respect to low content of pyruvate and high amount of fructose and glucose ranged in pyruvate content from 2.7 to 3.6 µmol mL^?1. These cultivars were juicy and contained low amounts of FOS and total flavonols. The most pungent onions contained the highest amounts of FOS among the cultivars: 4.53, 3.80 and 5.81 g per 100 g fresh weight (FW) respectively. They also had a high content of flavonols (86.6, 159.2 and 97.6 mg per 100 g FW) and high dry weight content (14.6, 13.5 and 15.6 g per 100 g). CONCLUSION: The sweetest onion cultivars were found to be ‘NUN 9746’, ‘Musica’, ‘Domenica Supersweet’, ‘Colossus’ and ‘Cronus’. The most pungent cultivars were ‘Powell Brown’ and ‘Tilbury’, which also contained the highest amounts of flavonols and gave the highest Trolox equivalent antioxidant capacity (TEAC) values among the 15 cultivars. Copyright © 2007 Society of Chemical Industry