甘薯蛋白质含量近红外反射光谱分析模型应用研究

以71份薯叶和170份薯块根样品为材料,应用近红外光谱技术(NIRS)和偏最小二阶乘法(PLs),建立甘薯蛋白质含量近红外反射光谱分析数学模型,并对模型预测结果的准确性进行了评价.结果显示.甘薯叶和块根的蛋白质含量的近红外光谱预测模型校正决定系数(R2cal)分别为O.996和0.993,校正均方差(RMSEE)分别为O.255和O.126,内部交叉验证决定系数(R2cv)分别为0.984和O.986,均方差(RMSECV)分别为0.448和O.178.模型对样品NIR的预测值与其相应的化学值有较好的相关性,此模型可用来预测甘薯蛋白含量.在甘薯优质育种和品质分析中具有广泛的应用价值.     

基于近红外光谱技术的大米品质分析与种类鉴别

应用近红外光谱(NIRS)技术建立了大米食味品质分析与种类快速鉴别的方法。提取了102份粉碎后大米样品的近红外光谱,采用偏最小二乘法(PLS)建立了大米水分、蛋白质和直链淀粉定量分析模型,对模型预测结果的准确性进行了评价。预测模型的内部交叉验证决定系数(R2)分别为:0.992、0.9792和0.9736;内部交叉验证标准差(RMSECV)分别为:0.141、0.201和0.209;模型外部验证决定系数(R2)分别为0.9861、0.912和0.9373;外部验证标准差(RMSEP)分别为0.179、0.206和0.243。通过计算样品的近红外光谱图之间的欧氏距离来反映不同样品间的差异,对不同属性和不同产地的大米进行了定性聚类分析,种类识别准确率达到100%。结果表明,NIRS分析技术可以用于对大米品质和种类的快速无损检测。     

基于近红外光谱与组合间隔偏最小二乘法的稻米镉含量快速检测

采用近红外光谱(near infrared spectroscopy,NIRS)结合组合间隔偏最小二乘法(synergy interval partial least squares,siPLS)建立稻米镉含量快速检测的方法。收集并分析72个稻米样品的NIRS谱图。对光谱前处理方法进行优化,确定平滑、多元散射校正与均值中心化处理为最优方法。采用siPLS法筛选特征波数,建立稻米镉含量的定量模型。稻米镉siPLS模型交叉验证均方根(RMSECV)与预测均方根(RMSEP)值分别为0.247与0.261,训练集相关系数(Rc)与预测集相关系数(Rp)值分别为0.919与0.895。结果表明:运用siPLS法选择特征波长后,不但可以降低模型的复杂度,同时还能够提高预测精度。NIRS作为一种快速、无损与便捷的初筛方法,可用于检测稻米中镉含量是否超标。     

双歧杆菌发酵对羊酸奶食用品质的影响

在使用传统发酵剂的基础上研究了添加双歧杆菌发酵对羊酸奶食用品质的影响情况,通过用单因素实验和正交实验,以羊酸奶的滴定酸度、保水力、感官评分和质构特性为指标,优化出双歧杆菌羊酸奶的最佳发酵工艺条件。结果表明:当加糖量为7%,接种量为6%(均为质量分数),菌种比例为1∶1∶2,培养温度为42℃时,双歧杆菌羊酸奶的食用品质最好。     

近红外光谱分析技术在糜子品质检测中的应用

为寻找一种简便易行的糜子籽粒水分、淀粉、粗蛋白、粗脂肪含量测定方法,以120个普通糜子品种为材料,采用近红外漫反射光谱(NIRS)法测定糜子籽粒水分、淀粉、粗蛋白、粗脂肪含量进行了研究。结果表明,采用一阶导数+减去一条直线、矢量归一化光谱预处理,分别建立水分、淀粉、粗蛋白、粗脂肪含量的校正模型,校正和预测效果最佳。模型的校正决定系数(R~2cal)分别为0.921 0、0.905 8,0.926 3和0.904 5,交叉验证决定系数(R~2cv)分别为0.921 0、0.900 2、0.940 0和0.881 2;外部验证决定系数(R~2val)分别为0.912、0.801、0.890和0.786。结果表明该模型代替化学分析法鉴定糜子品质是完全可行的。     

杂粮复合酸奶的感官评价与理化性质研究

以大豆为基础原料,添加杂粮糊液等成分,经过发酵制成了一种杂粮复合酸奶,并对酸奶样品进行蛋白质含量、p H值、持水性、流变学特性和质构性质等检测。同时,研究剪切速率对酸奶样品黏度的影响,以及杂粮糊液添加比例对酸奶的质构及感观性质的影响。结果表明,随着杂粮糊液的添加比例的提高,酸奶样品的表观黏度明显增加;7种酸奶的8项评价指标组间有显著差异(p0.05)。酸奶破裂强度与硬度相关性极显著(p0.01),胶黏性与光滑感相关性极显著(p0.01);质构硬度与感官硬度和适口性的相关性显著(p0.05),质构弹性与感官光滑感和适口性相关性显著(p0.05)。其中,杂粮糊液添加比例为11%(质量分数)的酸奶样品,综合评分最高,口感和风味最好。     

稻米储藏品质近红外光谱快速判定技术及仪器研发

采用近红外光谱(NIRS)分析技术和化学计量方法建立稻米脂肪酸值、品尝评分值和水分含量的近红外分析模型并对模型进行了预测准确性评价;在建立定标模型的过程中,分别探讨光谱散射和数学导数处理等优化对定标模型的影响。结果表明:偏最小二乘法是建立稻米脂肪酸值、品尝评分值和水分含量测定定标模型的最佳回归方法,所建立脂肪酸值、品尝评分值和水分含量模型的定标相关系数(RSQ)分别为0.961、0.9230和0.9999,定标标准偏差(SEC)分别为1.9205、2.5391和0.04。标准方法测定值与NIRS方法预测值之间的T检验结果显示两种方法无显著性差异,表明所建立的稻米脂肪酸值、品尝评分值和水分含量的NIRS数学模型有较好预测准确性。本试验研制了便携式粮食储藏品质测定仪。     

西式快餐用煎炸油质量近红外快速检测模型的建立

为对西式快餐用煎炸油质量进行快速监测,选用近红外光谱法（NIRS）联合偏最小二乘法（PLS）,分别建立酸价和极性组分两个煎炸油质量指标的定量模型。结果表明,酸价和极性组分的定标模型校正决定系数（R2）均为0.9974,校正标准差均方根（RMSEC）分别为0.111和0.359,预测标准差均方根（RMSEP）分别为0.171和0.562。盲样验证、精密度及准确度分析结果显示,酸价和极性组分的NIR预测值同真实值的相关方程的相关系数分别为0.9944、0.9761,应用所建模型预测同一煎炸油样品的酸价和极性组分的相对标准偏差（RSD）分别为0.934%和1.278%,表明所建模型对煎炸油样品的酸价和极性组分预测能力较好,且有较好的重现性。因此,基于近红外光谱定量模型,可以对西式快餐用煎炸油质量进行快速、准确地监测。     

应用便携式近红外仪检测生鲜羊通脊肉的嫩度

在北京市内收集生鲜羊通脊肉样品98个,研究应用便携式近红外仪快速无损检测生鲜羊通脊肉嫩度,结合化学计量学的方法建立可以快速无损检测生鲜羊通脊肉嫩度的近红外光谱检测模型。在建模过程中,研究了平滑、求导和信号校正等不同光谱预处理方法对模型的影响。结果表明:最佳的光谱预处理方法为均值中心化、Savitzky-Golay(SG)一阶导数、SG平滑和正交信号校正。应用偏最小二乘法建模所得模型的校正集标准偏差0.90、验证集标准偏差2.39、校正集相关系数(R c)=0.94、验证集相关系数(R p)=0.64、主因子数为4,说明模型具备较好的预测准确性,可应用于生鲜羊通脊肉嫩度的快速无损检测中。     

基于近红外光谱的大豆水分和粗脂肪含量的快速检测

基于近红外光谱技术快速检测大豆中水分和粗脂肪含量。方法 首先采集350-2500 nm光谱范围的大豆近红外光谱,采用光谱-理化值共生距离（SPXY）算法将大豆样本划分为校正集样本与测试集样本,然后对原始光谱分别采用多元散射校正(MSC)、标准正态变量交换(SNV)、归一化（Nor）等9种方法进行预处理,最后使用偏最小二乘回归(PLSR)分析方法建立模型对样本进行定量分析。结果 原始光谱经过多元散射校正后建立的偏最小二乘回归模型对水分的预测精度最高,其校正集和测试集的相关系数分别为0.8964和0.9055 , 均方根误差分别为0.4211和0.5933;原始光谱经过归一化处理后建立的偏最小二乘回归模型对粗脂肪的预测精度最高,其校正集和测试集的相关系数分别为0.9084和0.9295 , 均方根误差分别为0.6897和0.6462。结论 近红外光谱（NIRS）结合预处理及偏最小二乘回归法,可以快速、准确的检测大豆水分和粗脂肪含量。     

Effects of various whey proteins on the physicochemical and textural properties of set type nonfat yoghurt

In this study, the changes during storage in the physicochemical, textural and sensory properties of nonfat yoghurts fortified with whey proteins, namely whey protein concentrates (WPC), whey protein isolates and whey protein hydrolysates, were investigated. Enrichment of nonfat yoghurt with the whey protein additives (1% w/v) had a noticeable effect on pH, titratable acidity, syneresis, water‐holding capacity, protein contents and colour values on the 14th day of storage (P < 0.01). The addition of whey proteins to the yoghurt milk led to increases in the hardness, cohesiveness and elasticity values, resulting in improved textural properties. The addition of WPC improved the texture of set‐type nonfat yoghurt with greater sizes in the gel network as well as lower syneresis and higher water holding capacity. This study suggests that the addition of whey protein additives used for fortification of yoghurt gave the best textural and sensory properties that were maintained constant during the shelf life.     

Rheological and textural properties of goat and cow milk set type yoghurts

Yoghurts were made from pasteurised and homogenised goat milk (2.5% protein), goat milk fortified with a milk protein isolate (5% protein) and cow milk (3% protein), by acidification with a starter culture at 43 °C until a pH of 4.6 was reached. The rheological and textural properties of gels and yoghurts were analysed using dynamic low amplitude oscillatory rheology and back extrusion texture analysis. Gelation and fermentation times of goat milk were longer, while gelation pH, storage moduli (G′) and yield stress values were lower, compared with those of cow milk. Textural properties of goat milk yoghurts such as firmness, consistency, cohesiveness and viscosity index were very poor. Consequently, the products could not be classified as set type yoghurts. Fortification of goat milk with a milk protein isolate contributed to a significant improvement of the rheological and textural properties of yoghurt.     

Effect of long‐chain inulin on the texture profile and survival of Lactobacillus paracasei ssp. paracasei in set yoghurts during refrigerated storage

The effects of adding inulin at 20 g/L as a fat replacer and probiotic bacteria on the physicochemical and textural characteristics of yoghurt were studied. The ability of long‐chain inulin to improve the probiotic (Lactobacillus paracasei ssp. paracasei) bacteria viability in yoghurt was investigated. The addition of inulin made the texture (firmness, cohesiveness, adhesiveness and gumminess) of skimmed yoghurt similar to that of whole yoghurt, demonstrating the role of inulin as a fat replacer. However inulin increased syneresis and did not influence the viability of probiotic bacteria in the yoghurts. The addition of probiotic bacteria in yoghurts improved syneresis and increased firmness and gumminess.     

How do different cooling temperatures affect the characteristics of set-type yoghurt gel?

The impact of cooling temperatures on gel characteristics of set-type yoghurts was investigated through 28 days of storage. Yoghurt samples were cooled at four different temperatures (−10 °C, −5 °C, 0 °C, 4 °C) after incubation until the central temperature of yoghurt cups reached 4 °C. Cooling temperature and storage period were determined as significant factors affecting the yoghurt gel characteristics (p < 0.05). Yoghurts cooled at 0 °C clearly differed from the other yoghurts in terms of gel firmness and consistency. Confocal images of yoghurts cooled at 0 °C showed more homogeneous protein matrix than the other samples. Microbial counts and the acidity of the yoghurt samples increased with storage period. Textural parameters, water holding capacity and susceptibility to syneresis increased until 14th day of storage and then decreased. Sensory analysis of yoghurt samples confirmed the results obtained by microbiological and textural measurements.     

The physicochemical characteristics of nonfat set yoghurt containing some hydrocolloids

The effect of incorporating the hydrocolloids carrageenan (0.10%, 0.30%), xanthan gum (0.15%, 0.35%) and alginate (0.05%, 0.15%) in nonfat set yoghurt was examined in respect of instrumental texture profile and water‐holding capacity (WHC) of the yoghurt. The yoghurts which exhibited the similar behaviour of commercial yoghurts in terms of WHC, firmness and consistency, low adhesiveness and gumminess were analysed by difference‐from‐control sensory test. Carrageenan increased firmness, adhesiveness, gumminess and WHC at the highest concentration tested. The sensory tests did not show any significant difference between the formulations tested.     

基于TPA和Vis/NIR的番茄货架期的品质检测

针对番茄货架期的质地变化特点,采用质地多面分析方法(TPA)对番茄货架期的质构参数的变化进行了分析,通过TPA测试方法测得的典型的质构特性曲线,由该曲线计算出番茄的硬度,粘附性,内聚性,弹性,胶粘性,咀嚼性等质构参数,通过对各质构参数间的相关分析得出了相关矩阵表。结果表明,随着贮藏时间的延长,番茄各质构参数都有不同程度的降低,番茄的硬度和内聚性相关关系显著(P0.01),番茄的咀嚼性和其它的质构特性都存在相关关系(P0.05)。根据番茄货架期的质构参数变化规律,将番茄货架期分为货架前期(1~3 d),货架中期(4~6 d)和货架后期(7~9 d)。应用可见/近红外光谱(Vis/NIR)结合主成分分析方法(PCA)对不同货架期的番茄进行了检测分析,基于PC1和PC2的番茄货架期分类率为97%,为今后进一步分析建立水果和蔬菜货架期品质预测模型奠定了理论基础。     

Effect of total milk solid content adjusted by adding ultrafiltered milk retentate on quality of set mango yoghurt

The quality of set mango yoghurt prepared by varying total milk solids (TMS) level in mango yoghurt mix, by adding 5× ultrafiltered cow skim milk retentate and cow milk cream, was investigated. The water‐holding capacity (WHC) and values of textural attributes of mango yoghurt increased, whereas body and texture and overall acceptability scores decreased significantly (P < 0.05) with increasing TMS level. The optimised product (10.2% TMS level) was compared with conventional mango yoghurt. Acetaldehyde concentration, WHC, values of textural attributes, body and texture, overall acceptability scores and pH were significantly (P < 0.05) higher in optimised compared with conventional mango yoghurt.     

乳清蛋白-黄油乳液凝胶对低脂酸奶理化特性及品质的影响

乳液凝胶是一种新型的脂肪替代物,乳清蛋白和黄油是乳品中常用的原、辅料,利用乳清蛋白和黄油制作的乳液凝胶在乳制品加工中具有良好的应用前景。制备不同蛋白和脂肪含量的乳清蛋白-黄油乳液凝胶颗粒(whey protein-butter emulsion gel particles,WPI-EG),研究其对低脂酸奶理化特性及感官品质的影响,通过分析酸奶的持水力、质构、流变、微观结构及感官评价等指标,评价WPI-EG在低脂酸奶中的作用。结果表明,WPI-EG(5.5%蛋白质,7.9%脂肪)改善了酸奶的质构特性,硬度、稠度、黏聚性及胶着度显著增加,持水力增强。添加WPI-EG的实验组低脂酸奶的表观黏度显著高于对照组低脂酸奶。电镜结果显示,随着添加的WPI-EG中蛋白质和脂肪质量分数的增加,酸奶网络结构更加紧密。5.5%PR感官评价得分较高,具有较好的香气、润滑感和组织状态(酸奶中的WPI-EG添加量为10.9%)。研究显示,特定蛋白和脂肪含量的WPI-EG在酸奶中能够作为脂肪替代物和稳定剂,显著提升低脂酸奶的品质。     

Effects of sunflower honey on the physicochemical,microbiological and sensory characteristics in set type yoghurt during refrigerated storage

The primary purpose of this research was to monitor the influence of sunflower honey addition (2%, 4% and 6% w/v) to yoghurt milk on survival of the microbial flora of yoghurt and the physicochemical and sensory characteristics during refrigerated storage for 4 weeks. The water activity decreased according to the addition of honey with higher concentrations in the storage period (4°C). At the end of fermentation, pH values of yoghurt samples ranged between 4.33 (without honey) and 4.52 (addition of honey with 6%). The highest water holding capacity, consistency and the lowest brightness values were determined in the groups produced with 6% honey addition. The water holding capacity and a* (redness) values of the honey incorporated yoghurt samples increased during storage. Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus values of the yoghurt with honey increased compared with the control group samples (P < 0.01). Addition of honey to yoghurt milk has affected the vitality of the characteristics starters in the incubation and storage time of the yoghurt samples (P < 0.01). Optimum sweetness was obtained with the samples containing 4% honey level.     

胶原蛋白肽对凝固型酸奶品质的影响

为提高酸奶的品质和营养价值,以及定量评估胶原蛋白肽对凝固型酸奶品质影响,以牛乳为原料,通过添加不同量(0、0.2%、0.4%、0.6%、0.8%、1.0%、2.0%、3.0%、4.0%、5.0%)胶原蛋白肽,制备了胶原蛋白肽酸奶,并对其相关质量指标进行了测定。结果表明:胶原蛋白肽的添加显著提高了酸奶的持水能力、pH,降低了酸奶的硬度、粘性、胶着性、咀嚼性、滴定酸度,延长了酸奶的发酵时间,但对酸奶的弹性和内聚性无影响。胶原蛋白肽对酸奶品质的影响程度与其添加量有关,添加量≤ 0.6%时,随添加量的改变酸奶品质变化明显,添加量>0.6%时,随添加量的改变酸奶品质变化不明显。酸奶品质的变化与胶原蛋白肽对酸的发酵影响有关,发酵影响了酸奶网络结构的形成。本研究为定量评估胶原蛋白肽对酸奶品质的影响,建立了持水性、pH、酸度、硬度、粘性、胶着性、咀嚼性随胶原蛋白肽添加量变化的经验模型,为实际生产胶原蛋白肽酸奶奠定理论基础。