基于模糊综合评判的苹果酒酵母优选技术研究

为解决传统优选酿酒酵母方法——感官品评法的缺陷,以8株不同的酵母为试材,利用顶空法固相微萃取与气相色谱质谱联用(HS-SPME-GC-MS)鉴定了各自发酵所得苹果酒挥发性香气的主要成分;选取了对苹果酒总体香气质量贡献较大的7种高级醇类和6种酯类,并以2-辛醇为内标,测定了它们各自的含量,并构建了高级醇类和酯类的模糊综合评判隶属函数模型;结合感官品评,构建了感官得分的隶属函数模型;然后利用模糊综合评判法优选出了F14为最优苹果酒酿造酵母。结果表明本文提出的模糊综合评判法比传统的感官品评法具有优越性、客观性,能较全面的利用酒样信息。     

中华绒螯蟹不同部位中活性香气物质的研究

运用顶空固相微萃取-气-质联用技术(HS-SPME-GC-MS),对采自崇明的二级雄性中华绒螯蟹体肉、钳肉、足肉和性腺中的香气成分进行了鉴定并以内标法对其定量。大闸蟹四可食部位中共检测到8大类58种香气物质,根据阈值进一步求得每种香气物质的活性值(OAV值)。以OAV值为依据,从58种化合物中筛选得到了癸醛等15种最为关键的活性香气物质,并运用主成分分析法(PCA)和聚类分析法(CA)对其活性值进行了分析。由PCA分析得到:性腺样品香气品质较佳,戊醛等8种为表征"高品质风味"的特征性香气物质(其中2,4-庚二烯醛最为重要)。由CA分析得到:大闸蟹性腺样品可聚为一类,戊醛等8种活性香气成分也可聚为一类。主成分分析和聚类分析结果存在一致性且可以相互补充,今后可利用两种方法建立大闸蟹香气品质的评价模型。     

苹果酒酵母融合子W1发酵工艺参数的优化研究

该文利用所构建的苹果酒的模糊综合评判模型,以评判结果为目标,采用响应界面法研究了苹果酒发酵的规律,建立了优质苹果酒发酵的二次多项式数学模型,同时验证了模型的有效性,并考察了接种量、初始pH值和发酵温度对苹果酒品质的影响,优化出最佳发酵工艺参数为接种量5.33%、初始pH值3.37、发酵温度22.14℃。     

干制条件对红枣香气品质的影响

为探索干制条件对红枣香气品质的影响,采用固相微萃取结合气相色谱/质谱联用（SPME-GC/MS, solid phase microextraction coupled with gas chromatography mass pectrometry）技术分析鉴定了50、60、70℃热风干燥,自然阴干和糖心枣5种红枣样品的香气成分及相对质量分数,对红枣中7类主要香气物质进行主成分分析（principal component analysis,PCA）。结果表明影响红枣香气品质的主要香气物质种类为酯类、醛类、酸类和酚类;自然阴干的红枣香气品质较差,采用热风干制可有效提高红枣的香气品质;60℃热风干制的红枣香气成分综合得分最高,优于50℃和70℃热风干制红枣的香气品质,为红枣的干制工艺提供技术依据。主成分分析法可实现对红枣干制条件的区分,并能较好评价红枣的香气品质。     

不同酿造工艺对毛葡萄酒香气的影响

为探索酿造工艺对毛葡萄酒风味的影响,利用GC/MS法对秦巴山区野生毛葡萄在两种工艺条件下酿造的葡萄酒的香气成分进行了研究。结果表明：用传统工艺及CO₂浸渍工艺酿造的毛葡萄酒醇类相对含量最高,其中以苯乙醇、戊醇含量最高。在酯类、酮类、酚类方面,两种工艺酿造的原酒比陈酿6个月的酒种类少,相对含量低;而对于其他香气成分,则是原酒高于陈酿6个月的酒。说明一定时间的陈酿对于毛葡萄酒的香气质量有所提高。通过对两种工艺的综合比较发现,传统工艺酿造的原酒香气质量优于CO₂浸渍工艺酿造原酒;但经过6个月的陈酿后,CO₂浸渍工艺酿造酒香气质量却高于传统工艺的酿造酒。     

基于因素法和SVM模型的耕地质量评价方法研究

为减少耕地质量评价工作中确定评价指标权重人为因素的影响,选取江西省奉新县为研究对象,引入机器学习技术,建立基于SVM模型的耕地质量评价模型,探索客观、高效的耕地质量评价方法。本文应用因素法和SVM模型法分别对奉新县耕地质量等别进行划定,通过对比分析两种方法的评价结果,对两种方法的优劣及适用条件进行了判定。结果表明,与因素法相比,SVM模型法具有等别划分高效的优势;SVM模型法耕地质量评价结果的正确率高达96.93%,符合耕地质量评价精度要求。应用SVM模型进行耕地质量评价具有测算高效、受人为因素干扰小等优点,可以广泛应用于耕地质量等别更新、新增耕地质量等别划定等工作。     

酵母菌PA4酿造苹果酒发酵条件的优化

通过三因素二次正交旋转回归实验设计，考察了发酵温度、接种量、发酵液初始pH值对酵母菌PA4酿造苹果酒品质的影响，得出苹果酒质量与影响因素的回归模型。结果表明：发酵温度和接种量对苹果酒质量的影响极显著(p＜0.01)，发酵液初始pH值对苹果酒质量的影响显著(p＜0.05)；菌株PA4酿造苹果酒的最佳工艺参数是发酵温度为24℃，接种量为10%，pH值为3.4。     

基于原烟外观图像和近红外光谱的烟叶感官质量模型研究

为了探讨不同产地、不同等级以及不同品种来料烟外观指标、物理特性及近红外光谱对其感官质量的影响,找到一种可以客观反映烟叶感官质量的方法。选取了四川3个产地、3个部位、10个等级和2个品种的单料烟,以组为单位进行采集,每组10片,共采集烟叶7897片。使用变量标准化(SNV)方法对原始光谱数据进行校正,用Standard Scaler方法对烟叶外观指标、物理特性、校正后的光谱数据进行标准化。采用主成分分析(PCA)法对数据进行降维。分别运用二次判别分析算法(QDA)、K近邻算法(KNN)、支持向量机(SVC)构建训练模型,用Grid Search CV算法进行超参优化,以平衡准确率作为模型评价指标。结果表明,3个训练模型中,SVC的泛化能力最优。其中,香气风格彰显程度、香气质、香气量、杂气、浓度、劲头、刺激性、余味及甜感的预测平衡准确率分别为0.747、0.751、0.715、0.720、0.712、0.774、0.685、0.725、0.700。外观指标、物理特性及近红外光谱共同影响着烟叶的感官质量。     

基于主成分分析和判别分析的白酒品牌鉴别方法

白酒的香气物质决定了白酒产品的差异。为了实现不同白酒产品的区分鉴别,提出了基于气相色谱分析技术结合模式识别实现白酒区分的方法。采集了7种产品共70个白酒样本的气相色谱数据,定性定量分析了己酸乙酯、乳酸乙酯等10种基本香气物质的含量,并对测定的物质进行主成分分析,验证区分效果,最后利用线性判别法建立判别函数,对不同白酒进行区分。结果表明,2种分析方法均可用于区分不同白酒,主成分分析结果显示,前3个主成分累计贡献率为86.527%,能有效描述香气物质和产品之间的复杂关系;线性判别分析对所有样本均得到准确的判别,正确率为100%,对预测样本的正确判别率达93.9%,建立的判别函数能准确区分不同白酒。研究表明,利用气相色谱技术结合模式识别的方法可用于不同白酒的区分鉴别。     

6种食用芳香植物挥发性成分的GC-MS/GC-O分析

挥发性成分是芳香植物具有多样风味及香气性能的物质基础。为研究常见可食用芳香植物的挥发性成分及其风味特性的异同,构建特色芳香植物风味数据库,利用气相色谱-质谱联用技术分析经顶空法萃取的6种食用芳香植物(薄荷、藿香、罗勒、丁香罗勒、香薷及密花香薷)的挥发性成分,经气相嗅辨仪对其挥发性成分进行香气描述分析,对比研究6种芳香植物挥发性成分的异同及香气性能的差异。结果表明:6种芳香植物香气主要由萜烯类、醇类、酮类、醛类成分组成,含有少量的酯类、杂环类及芳香族类化合物,多具有辛辣、刺激、樟脑样香气及清新的柠檬、柑橘风味。薄荷中以具花香和柠檬样香气的香叶醇、香茅醇及柠檬醛、香叶醛含量较多;藿香中以左旋薄荷酮及草蒿脑为主,具木香及大茴香似香气特征;罗勒中丙烯酸酯和芳樟醇是其主体成分,辛辣味突出,花香显;而丁香酚成就了丁香罗勒的主体风味,似丁香花香,具辛辣香气;香薷中以具柠檬样香气的D-柠檬烯、柠檬醛、γ-萜品烯为主,柠檬醛和香叶醛为密花香薷的主体成分,整体偏辛辣,花香透,伴柠檬样清新香气。不同的挥发性成分,以一定的比例及含量组成呈现了芳香植物的特征香气。研究结果可为特色芳香植物的品种选育、香气品质提升及风味性能的研究提供科学数据参考。     

Characterization of Royal Gala apple aroma using electronic nose technology-potential maturity indicator

Changes in aroma of apple harvested at four different maturities were measured at harvest and after short-term storage using electronic aroma sensors ("electronic nose") and classical headspace/gas chromatography methods. Stored fruits were also evaluated by a trained sensory panel. Compared with headspace/gas chromatography, the electronic nose was found to be more sensitive ( approximately 40 times) in terms of sample size. The sampling procedure for the electronic nose was much less complex. Using discriminant function analysis, both methods classified the apples tested into groups according to harvest date. After storage, the groupings were more diffuse. Results from sensory testing showed partial separation along the first linear discriminant but did not classify the apple into distinct groups. Important differences between treatments were found for "overall flavor", "acid flavor" intensity, "crispness", "cider/fermented aroma", "vegetative aroma", and "canned pear aroma".     

Characterization of aroma compounds in apple cider using solvent-assisted flavor evaporation and headspace solid-phase microextraction

The aroma-active compounds in two apple ciders were identified using gas chromatography-olfactometry (GC-O) and GC-mass spectrometry (MS) techniques. The volatile compounds were extracted using solvent-assisted flavor evaporation (SAFE) and headspace solid-phase microextraction (HS-SPME). On the basis of odor intensity, the most important aroma compounds in the two apple cider samples were 2-phenylethanol, butanoic acid, octanoic acid, 2-methylbutanoic acid, 2-phenylethyl acetate, ethyl 2-methylbutanoate, ethyl butanoate, ethyl hexanoate, 4-ethylguaiacol, eugenol, and 4-vinylphenol. Sulfur-containing compounds, terpene derivatives, and lactones were also detected in ciders. Although most of the aroma compounds were common in both ciders, the aroma intensities were different. Comparison of extraction techniques showed that the SAFE technique had a higher recovery for acids and hydroxy-containing compounds, whereas the HS-SPME technique had a higher recovery for esters and highly volatile compounds.     

Production and composition of cider spirits distilled in "alquitara"

The capacity of alquitara (a traditional distillation system) to produce cider brandies is evaluated. To do so, the chemical composition of 12 fractions obtained during the distillation process and the cider brandies obtained from five ciders were analyzed (alcohol strength, methanol, volatile substances, furfural, and metals), taking into account European and Spanish legislation. During the course of distillation, an important increase in methanol, furfural, 2-phenylethanol, and metals in the last fractions was observed, while fusel oils were more abundant in the first fractions collected. Only acetaldehyde behaved differently, showing a minimum concentration in the middle fractions that might be explained by its formation on the surface of alquitara. On the other hand, the final distillates obtained by means of this method complied with the considered regulations. Worth highlighting in this regard are the low levels of a potential toxin such as methanol, as well as the detection of a constant ratio for methanol, ethanol, and fusel oil for the pairs of cider/spirits analyzed, which could be interpreted as an indication of good uniformity in the distillation system and method, thus guaranteeing product quality.     

Effect of gas environment and sorbate addition on flavor characteristics of irradiated apple cider during storage

Apple cider, with (0.1%) and without potassium sorbate, was packaged in polystyrene containers and exposed to three different gas environments: oxygen flush, nitrogen flush, and atmospheric air. To evaluate the effects of irradiation (2 kGy) and storage on flavor and microbial quality, these irradiated apple cider samples were compared to a control, unirradiated sample exposed to atmospheric air. Volatile compounds, soluble solids, titratable acidity, and microbiological counts were determined weekly throughout 7 weeks of refrigerated (4 degrees C) storage. Cider irradiated and stored in atmospheric air or nitrogen-flush environments had lower rates of loss for characteristic flavor volatiles compared to unirradiated apple cider and cider irradiated and stored in an oxygen-flush environment. The addition of potassium sorbate to the apple cider resulted in lower counts of yeasts and aerobic microorganisms, reduced fermentation of sugars to organic acids, and improved retention of volatile compounds characteristic of apple cider.     

Furan formation in sugar solution and apple cider upon ultraviolet treatment

Furan is a possible human carcinogen induced by thermal processing of food. While ultraviolet C (UVC) is used to decontaminate apple cider and to sterilize sugar solutions, it is unknown whether UVC induces furan formation in cider or solutions of its major components. This study was conducted to investigate the possible formation of furan by UVC in apple cider and in solutions of common constituents of apple cider. Our results showed that UVC treatment induced furan formation in apple cider, and the major source of furan was apparently fructose. UVC treatment (at incident doses up to 9 J/cm (2)) of fructose solutions produced a higher amount of furan, while very low concentrations of furan were induced by UVC in glucose or sucrose solutions, and virtually no furan was induced by UVC from solutions of ascorbic acid or malic acid. When an isotope (d(4)-furan) of furan was treated with UVC, d(4)-furan was destroyed rapidly even at low doses in fructose solution, suggesting that the accumulation of furan is the balance between destruction and formation. The UV sensitivity of E. coli K12 (a surrogate of E. coli O157:H7) in two sources of apple cider was also determined. At UVC doses that could inactivate 5-log of E. coli, very low concentrations (<1 ppb) of furan were induced. Our results suggest that UVC could induce furan formation, but when used for the purpose of juice pasteurization, little furan was induced in apple cider.     

Chemical characterization of asturian cider

Ninety-four samples of Asturian natural cider were analyzed for titratable and volatile acidities, pH, alcoholic, total polyphenol, and acidic polysaccharide contents, nonvolatile acids, polyalcohols, residual sugars, and major volatile compounds. A partial least-squares regression analysis (PLR-1) was performed to correlate the chemical composition and the origin of the raw material, the cider samples being grouped into two categories: an "odd" class, cider made from foreign apples (1995 and 1997), and an "even" class, ciders made from Asturian apples (1996 and 1998). The mathematical model has a multiple linear correlation coefficient of 80%.     

Gas chromatographic analysis of total fatty acids in cider

This paper reports the composition of total fatty acids in an apple beverage, cider. Fatty acids are present in the free or esterified form and contribute to both the flavor and foam properties of cider. Fatty acids were separated and identified as methyl esters by GC-MS, and 12 of these were subsequently determined by GC-FID. The major fatty acids found in cider were caproic, caprylic, capric, and palmitic acid, the saturated acids predominating over the unsaturated ones. The proposed method was applied to 59 ciders from three consecutive harvests (1996, 1997, and 1998), which were made by 19 cider-makers from the region of Asturias (Spain). Linear discriminant analysis of fatty acids in these samples allowed selection of palmitoleic, pentadecanoic, linoleic, myristic, and linolenic acid as the most predictive variables to differentiate ciders made from apples grown in the Asturias region (1997 harvest) and ciders made from apples grown outside this region (1996 and 1998 harvests).     

Quality assessment of strawberries (Fragaria species)

Several cultivars of strawberries (Fragaria sp.), grown under different conditions, were analyzed by both sensory and instrumental methods. The overall appreciation, as expressed by consumers, was mainly reflected by attributes such as sweetness and aroma. No strong correlation was obtained with odor, acidity, juiciness, or firmness. The sensory quality of strawberries can be assessed with a good level of confidence by measuring the total sugar level ( degrees Brix) and the total amount of volatile compounds. Sorting out samples using the score obtained with a hedonic test (called the "hedonic classification method") allowed the correlation between consumers' appreciation and instrumental data to be considerably strengthened. On the basis of the results obtained, a quality model was proposed. Quantitative GC-FID analyses were performed to determine the major aroma components of strawberries. Methyl butanoate, ethyl butanoate, methyl hexanoate, cis-3-hexenyl acetate, and linalool were identified as the most important compounds for the taste and aroma of strawberries.     

皖南烟叶香气成分因子及关联度分析

为探讨各类香气物质对皖南地区烟叶特殊香型形成的作用,本试验对皖南地区四种典型土壤所产烟叶香气进行了因子分析,及香气综合评定值与土壤养分的关联度分析。结果表明:利用因子模型在阐明以因子形式表现的香气物质变量间的关联时,可信度高。因子分析证明类胡萝卜素类物质降解产生的香气物对烤烟香气影响最显著,可推断烤烟的香气特色主要是由烟叶中类胡萝卜素类降解产物的量及协调程度决定的,这其中又以巨豆三烯酮最为重要。在皖南地区烟株生长及香气品质形成过程中,土壤pH值起重要作用,土壤速效钾、全磷影响作用逐渐增加,碱解氮、有机质影响作用逐渐降低。