不同油炸时间的马铃薯片油脂吸收规律

为了表征不同油炸时间下马铃薯片的油脂吸收规律,该文结合索氏抽提、染色法、激光共聚焦扫描镜观察、低场核磁共振成像技术等方法对马铃薯片的油脂吸收规律进行描述和解释,获得了油炸温度180℃、油料比10:1时不同油炸时间下马铃薯片油脂含量、油脂类型以及油脂分布的变化规律,并结合其孔隙特征解释油脂的吸收行为。结果表明:油炸时间(0~12 min)显著影响马铃薯片的总油脂质量分数、表面油脂、结构油脂和表面渗透油脂质量分数(P0.05);随着油炸时间的延长,马铃薯片的总油脂质量分数逐渐上升,当油炸10 min后,总油脂质量分数达到47.09%,之后逐渐趋于稳定;马铃薯片的表面油脂质量分数最低,约1.30%~2.06%;随油炸时间的延长,结构油脂质量分数逐渐上升,而油炸6 min后马铃薯片的表面渗透油脂质量分数呈下降趋势;激光共聚焦扫描镜观察显示,油炸过程中,随着油炸时间的延长,马铃薯片红色区域面积增大,表明油脂质量分数增加,且油脂从表面逐渐向中心渗透,黏附于细胞壁上,充盈细胞间质;当油炸时间为0~8 min时,马铃薯片的孔体积和孔隙率随油炸时间而增大,对应的油脂质量分数也逐渐提高,研究结果可为油脂吸收的表征,以及低油马铃薯片的开发提供参考。     

应用可见/近红外高光谱成像测定鲑鱼片脂肪含量分布(英文)

脂肪作为一种重要的品质参数,在大西洋鲑鱼片中的分布很不均匀。为寻找一种能替代脂肪化学检测的快速无损的方法,该研究应用可见/近红外高光谱成像测定大西洋鲑鱼片的脂肪含量分布。分别采用可见/短波近红外(400-1100 nm)和近红外(900-1700 nm)系统获取大西洋鲑鱼片样本的高光谱图像。提取样本图像的平均光谱并与其相应的脂肪含量化学值采用偏最小二乘回归(partial least squares regression,PLSR)和最小二乘支持向量机(least-squares support vector machines,LS-SVM)建立相关性模型。为降低高光谱图像的共线性和冗余度,基于竞争性自适应重加权算法(competitive adaptive reweighted sampling,CARS)分别在可见/短波近红外和近红外光谱区间提取16个(468,479,728,734,785,822,863,890,895,899,920,978,1005,1033,1040,1051 nm)和15个(975,995,1023,1047,1095,1124,1167,1210,1273,1316,1354,1368,1575,1632,1661 nm)特征波长,并分别建立PLSR和LS-SVM模型。特征波长模型的性能优于全波段模型,且近红外区间的特征波长PLSR模型为最优,预测决定系数(R2p)为0.92,预测均方根误差(root mean square error of prediction,RMSEP)为0.92%,剩余预测偏差(residual predictive deviation,RPD)为3.50。最后,将最优模型用于预测高光谱图像上所有像素点的脂肪含量以展示样本上脂肪的分布。此外,还基于该技术对大西洋鲑整鱼片实现了脂肪分布可视化。结果表明高光谱成像技术结合化学计量学方法在大西洋鲑鱼片脂肪的定量和分布可视化上有一定的研究和应用前景。     

降低油炸土豆制品吸油率方法与机理研究

为探索有效的降低油炸制品含油率的方法与理论,该文以油炸土豆条为对象,考查了深层油炸过程和冷却过程的吸油动力学特征,结果表明油炸制品吸油过程主要是发生在冷却早期阶段。分别比较不同真空条件下物料起始吸油时间以及20～45s过程Patm-Pv值大小,进一步发现延滞物料壳层开始吸油时间以及降低壳层内、外压差值的大小,均能够促进物料表面浮着油滴落,实现降低油炸制品含油量的目的。当冷却环境压强为80kPa时,所得总吸油率最小为13.6%,该研究可为油炸食品工业探索降低含油率加工工艺提供参考。     

煎炸油中产生的极性成分对食品微观结构和质构的影响

研究了煎炸油中产生的极性成分对食品微观结构和质构的影响。用硅胶柱色谱和高效体积排阻色谱测定了极性成分和聚合物含量变化，油炸食品穿孔力和微观结构的变化分别用质构仪和显微镜进行测定和观察。结果表明随着油炸时间延长，极性成分、聚合物含量呈线性增加且二者间也呈线性关系,油炸食品的微观结构越来越差,食品穿孔力虽没有明显变化，但其剪切系数(Kp)有增加而压缩系数(Ka)有减小的趋势。油脂中的极性成分严重影响了食品的微观结构，也在一定程度上影响了食品的Ka、Kp值，但还不能完全通过Ka、Kp的变化来表示油品质对食品质构的影响。     

基于均匀设计和主成分分析的甘薯薯片常压油炸工艺优化

常压油炸甘薯薯片伴有含油量高、颜色不佳等问题,阻碍了甘薯薯片常压油炸加工的发展。为优化甘薯薯片常压油炸工艺,采用均匀设计法,以含油量、含水量、L*值、b*值为指标进行四因素八水平的试验,并对数据进行多元回归分析。结果表明,含油量受各因素影响顺序为:油炸时间预干燥温度油炸温度预干燥时间;含水量受各因素影响情况符合二次多项式回归模型;L*和b*均主要受油炸时间和油炸温度的影响。指标主成分分析表明,提取的2个主成分能解释90.09%的指标信息,达到指标降维目的;岭回归分析建立的综合得分回归模型拟合度R2=0.9943,能很好的拟合产品的综合得分;偏最小二乘法回归分析预测最佳综合评分工艺参数为:预干燥温度90℃、预干燥时间20min、油炸温度120℃、油炸时间4min,验证综合评分0.82,综合评分高于均匀设计试验组最高值0.80。综上可知,优化工艺所得产品具有含油量低、含水量低、颜色佳等特点,相关模型具有良好的预测能力。本研究结果为甘薯的实际生产加工及研究提供了工艺参考。     

油用牡丹单粒种子含油量NIRS模型的建立

为了建立油用牡丹单粒种子含油量的近红外测定模型,便于高含油量单株的选育,采用索氏抽提法测试了200份油用牡丹凤丹单粒种子的含油量,并应用近红外反射光谱技术(NIRS)采集了200份样品的光谱数据,通过偏最小二乘法(PLS)和主成分回归法(PCR)构建了油用牡丹单粒种子含油量的数学模型。结果表明,索氏抽提法中,均匀粉碎后的油用牡丹籽样品干燥烘焙条件为105℃ 2 h,牡丹籽抽提时间为20 h,测出的含油量变化范围在10%~28%之间,籽油含量基本符合正态分布。NIRS法构建的模型最佳参数为:采用PLS法,光程固定,一阶导数消除背景,数据平滑处理采用Norris derivative filter的方法,平滑参数选用5和3。内部交叉检验校正相关系数r₁为0.980 1、预测相关系数r₂为0.957 6、校正均方根误差(RMSEC)为0.463、预测均方根误差(RMSEP)为0.705。外部检验相关系数达 0.957 6, 平均误差小于3%。本试验所构建的牡丹单粒种子含油量的NIRS模型可靠,可以用于分析油用牡丹单粒种子的含油量。     

沙门氏菌生物菌膜的结构特征及在食品接触面的转移

为探明沙门氏菌生物菌膜的结构特征及其在食品加工接触表面的转移率,以TSB为标准生长基质,研究了沙门氏菌在TSB和肉质液(MTLB)2种培养基质中形成的生物菌膜结构特征,并利用"夹心粘附法"测定2种生物菌膜在常见的5种食品加工接触材料表面的转移率。结果表明:沙门氏菌在TSB中的生物菌膜形成数量显著大于MTLB;激光共聚焦扫描显微镜(CLSM)结果显示,沙门氏菌在MTLB中形成的生物菌膜结构特征偏向于片状聚集的云雾状结构,而在TSB中则呈现密集分布的网状结构;扫描电子显微镜(SEM)结果表明,2种基质中所形成的生物菌膜微观聚集体结构无明显差别;2种生物菌膜在5种食品接触面的转移率存在显著差异,MTLB中的生物菌膜在不锈钢和玻璃表面的转移率较高,TSB中的生物菌膜在聚乙烯表面的转移率较大。本研究可为沙门氏菌风险评估提供基础数据,为改进沙门氏菌的清洗控制措施提供参考。     

热风干燥对果蔬薄壁组织细胞结构的影响

为了研究热风干燥过程对果蔬微观结构的影响,该文选择马铃薯、苹果、胡萝卜3种物料,运用组织石蜡制片、显微成像及图像处理技术,获得了3种物料在热风干燥过程中不同含水率下的薄壁组织细胞结构图像及各细胞结构参数的分布曲线,并分析了热风干燥对微观结构参数(细胞横截面积、周长、当量直径和圆度)的影响,建立了微观结构参数与宏观干燥参数(水分比)的拟合方程。结果表明,各细胞结构参数比与水分比之间具有线性相关性,可以用数学模型预测在热风干燥过程中苹果、马铃薯和胡萝卜的薄壁组织细胞结构随含水率的变化情况,研究结果可为控制果蔬在热风干燥条件下的品质及建立干燥过程数学模型提供理论依据。     

不同环境条件甘蓝型油菜含油量钝感系数的QTL分析

本研究以甘蓝型油菜GH06和中油821为亲本杂交,后代通过＂一粒传法＂连续自交8代构建重组自交系群体SWU-2为材料,利用本实验室已构建的遗传连锁图谱和复合区间作图法（CIM）对三个不同环境下含油量及含油量环境钝感系数进行QTL分析。结果表明：（1）不同环境中共检测到49个含油量相关QTL分别位于10个不同连锁群上,单个QTL可解释3.31%~12.47%的表型变异,42个含油量环境钝感系数QTL分别位于12个不同连锁群上,单个QTL可解释表型变异的4.05%~14.68%;（2）7个含油量相关的QTL与含油量钝感系数QTL相互重叠,分别位于第1、5、8、10、15和20连锁群上。研究结果表明明甘蓝型油菜含油量相关性状表现为多基因控制的数量性状,基因表达受环境影响较大,本研究为甘蓝型油菜含油量钝感基因的筛选提供了依据,有助于促进甘蓝型油菜高油稳油分子标记辅助育种的发展。     

基于序列图像三维重建的稻种品种识别

利用机器视觉技术识别稻种表面形态,从而识别种子纯度,可以为种子品质确定提供一种快速精确的技术方法。该文应用序列图像聚焦测度法进行了稻种三维重建,在稻种的品种识别中,将三维特征作为识别依据,相对传统方法仅采用二维图像特征作为识别手段,具有稻种形态测量参数值更精确,外观特征及缺陷表达更全面的优势。该方法通过分析显微镜平台获取的多幅不同对焦距离的图像序列,计算聚焦测度和焦点深度值。结合序列图像聚焦测度法与表面纹理重现,实现稻种形态表面三维重建。通过构造BP神经网络模型,利用测量所得三维立体特征值进行稻种的品种识别,筛选适合稻种检测的BP神经网络算法。试验结果表明,序列图像方法应用于稻种三维重建,其测量精度可达到5μm,将测量所得的三维特征值作为参数进行5个稻种的品种识别,识别率在90%以上。该研究可为农作物品种识别中三维形态及纹理特征的研究提供参考。     

速冻莲藕片贮藏过程中品质变化动力学模型

为了探寻贮藏温度对速冻莲藕片品质的影响及预测其货架期,该文研究在贮藏温度?5、?15和?25℃条件下,速冻莲藕片维生素C、色泽和硬度随着贮藏时间的变化,建立了3个指标变化动力学模型。结果表明:随着贮藏温度的升高,速冻莲藕片维生素C、色泽和硬度的变化速率逐渐增加,?5℃条件下贮藏的速冻莲藕片品质快速下降,?15和?25℃条件下贮藏前期莲藕片品质下降不显著(P0.05),随着时间的延长,?25℃部分玻璃态贮藏的莲藕片品质最佳;不同贮藏温度下速冻莲藕片维生素C和硬度变化符合一级反应,总色差和亮度变化符合零级反应,速冻莲藕片维生素C、色泽和硬度反应速率常数符合Arrhenius方程,并建立莲藕片货架期动力学模型,通过对其验证发现模型拟合度良好(R20.9),能预测速冻莲藕片贮藏期各品质指标变化和不同温度下的货架期寿命。研究结果可为速冻莲藕片低温贮藏品质变化和货架寿命预测提供理论依据。     

煎炸次数对大豆油及薯条脂质中极性组分的影响

采用中压快速制备型色谱-高效体积排阻色谱技术,探索了煎炸次数对大豆油及薯条表面所吸附油脂中极性化合物总量(total polar compounds,TPC)及其组分的影响。结果表明,煎炸薯条后剩余的大豆油中的TPC总量随着煎炸次数的增加而是逐渐增加,而薯条表面所吸附油脂中的TPC含量也随之逐渐增加;同时,煎炸次数的增加,显著改变了极性组分氧化甘油三酯寡聚物(oxidized triglyceride oligomers,TGO)、氧化甘油三酯二聚物(oxidized triglyceride dimers,TGD)、氧化甘油三酯单体(oxidized triglyceride monomers,ox-TG)在大豆油中的分布,而甘油二酯(diacylglycerols,DG)的含量增加缓慢,游离脂肪酸和甾醇(free fatty acids and sterols,FFAsterols)和其他未知小分子化合物的含量呈现波动性变化。煎炸次数严重影响了大豆油和薯条表面所吸附油脂中的TPC及其组分分布,也在一定程度上影响了薯条的健康价值。     

Effective ways of decreasing acrylamide content in potato crisps during processing

The aim of this work was to examine the effect of blanching or soaking in different acid solutions on the acrylamide content in potato crisps. Furthermore, the effects of a shorter frying time and a lower frying temperature combined with a postdrying were investigated. Soaking or blanching of potato slices in acidic solutions decreased the pH of potato juice and increased the extraction of amino acids and sugars. Potato crisps obtained after such pretreatments were characterized by lower acrylamide content. The most effective extraction of free amino acids and sugars as well as the largest decrease of acrylamide content (90%) in crisps was obtained when potato slices were soaked in acetic acid solution for 60 min at 20 degrees C. Shorter frying time followed by postdrying resulted in low-moisture potato crisps. Furthermore, the postdrying treatment gave a decreases in acrylamide content of approximately 70% when potato slices were fried at 185 degrees C and approximately 80% when potato slices were fried at 160 degrees C. Effective ways of decreasing acrylamide content in crisps production have been found. Crisps with low acrylamide content and good sensory quality can be obtained either by blanching in acetic acid as pretreatment or by a short frying followed by postdrying.     

Spinach (Spinacia oleracea) powder as a natural food-grade antioxidant in deep-fat-fried products

The addition of spinach (Spinacia oleracea) powder in flour dough as a natural antioxidant was investigated, and oxidation of frying oil and the lipid in fried products during frying was also studied. Flour dough with spinach powder was rolled into sheets of 0.1 cm thickness and then cut into squares to be fried. Each frying was performed in 160 degrees C soybean oil for 1 min, repeated every 20 min for 20 h. Fried samples were analyzed immediately or after being stored at 60 degrees C for 12 days under dark. The lipid content of fried dough was lower in samples with the addition of spinach powder. Spinach in the dough decreased accumulation of the polar compounds in soybean oil during frying but had little effect on the fried dough. It also reduced conjugated diene and aldehyde formation in the lipid of fried dough during storage. Improvement in lipid oxidative stability, presumably due to pigments in spinach, was more noticeable in the fried products during storage than in the frying oil.     

Effects of Different Drying Processes on Oil Absorption and Microstructure of Tortilla Chips

Tortilla chips were slow dried after baking and then fried in fresh soybean oil. Control chips were not dried before frying. Final oil content of sun-dried tortilla chips was significantly (P < 0.05) lower than those receiving the control treatment. As a result of drying, the structure of the tortilla chips was tighter before frying but expanded significantly during frying. An attempt was made to produce tortilla chips with the same characteristics of the sun-dried chips using impinging hot-air drying techniques. Results indicated that tortilla chips drying rate was mostly affected by air temperature; texture was crispier at higher air temperatures; shrinkage of the piece was higher at lower convective heat transfer coefficient; and microstructure looked smoother at higher air temperature.     

Enhancing quality and oxidative stability of aged fried food with gamma-tocopherol

To determine the effects of gamma-tocopherol on the stability of fried food, potato chips were fried in triolein with 0, 100, or 400 ppm gamma-tocopherol. Potato chips, sampled at 1, 3, and 6 h of frying time, were aged for 0, 2, and 4 days at 60 degrees C and then evaluated for odor attributes by sensory analysis and for volatile compounds by purge-and-trap gas chromatography-mass spectrometry. Oil sampled after 1, 3, and 6 h of frying time from the fryer was evaluated for total polar compounds and retention of gamma-tocopherol. Oil extracted from the potato chips was also analyzed for residual gamma-tocopherol. gamma-Tocopherol disappeared rapidly, with only slight amounts of the original 100 ppm level detectable after the triolein was used for frying. gamma-Tocopherol significantly inhibited polar compound production in the triolein. Results showed that gamma-tocopherol inhibited the oxidation of the fried food even when only very low levels of retained gamma-tocopherol were present in the frying oil or potato chips. Nonanal formation was inhibited by gamma-tocopherol in aged potato chips. Odor analysis of the aged potato chips showed that samples with 0 ppm gamma-tocopherol had a rancid odor after being aged for 4 days. Potato chips with 400 ppm gamma-tocopherol had no rancid odors; however, as the level of gamma-tocopherol decreased in the triolein and in the potato chips, a weak plastic odor characteristic of oxidized triolein was detected.     

Utilization of Oxidized and Cross-Linked Corn Starches in Wheat Flour Batter

Starch is often added to batters to improve the texture and appearance of fried food products. However, comparisons of commercially available starches in terms of batter characteristics are rare. In this study, various corn starches, native or modified, were mixed with wheat flour (20% dry solids basis), and the physical properties of the batters after deep-fat frying were examined. Native corn starches of different amylose contents (high-amylose, normal, and waxy) and chemically modified corn starches (oxidized and cross-linked) were tested. The batter was prepared by adding water to the starch-flour mixtures (42% solids) and deep-fat frying at 180°C for 30 sec. The texture of the fried batter was analyzed using a texture analyzer (TA) with a Kramer shear cell. The pasting viscosity profile of the starch-flour mixtures (7% solids in water) was also measured with a Rapid Visco Analyser. When the native corn starches of different amylose contents were compared, the crispness (peak number before breakage) and hardness (maximum peak force) measured using the instrument were positively correlated with the amylose content in starches but negatively correlated with the residual moisture content of the fried batters. The peak viscosity and breakdown in viscosity profiles of the starch-flour mixtures were also negatively correlated with crispness. The use of high-amylose corn starch was effective not only in increasing the crispness, but also in reducing the oil uptake. However, the fried batter containing high-amylose starch was denser and harder than the batter containing normal starch. Among the modified starches tested, oxidized (0.4% active Cl₂) and cross-linked (4% 99:1 mixture of STMP and STPP) starches showed improvements in the overall properties of the fried batters. With excessive oxidizations (>0.4% Cl₂), however, the crispness was reduced.