添加益生元对酸乳凝胶过程及微观结构的影响

为研究菊粉、低聚果糖和低聚半乳糖3 种益生元对酸乳凝胶过程及微观结构的影响,以未添加益生元的酸乳为对照,利用光学微流变仪、Turbiscan稳定分析仪和扫描电子显微镜分别检测添加益生元酸乳在发酵期间及后熟贮藏期间流变学参数、稳定性和微观结构,并进行对比研究。结果表明：添加菊粉更有助于酸乳形成较为均匀、疏松的微观结构;含低聚果糖的酸乳固液平衡值低于0.5,更有利于增强酸乳的固体性质;添加低聚半乳糖的酸乳微观稳定性较好。因此,3 种益生元对酸乳的凝胶过程及微观结构的影响各不相同,未来还可对3 种益生元进行复配处理,添加到酸乳中进一步探究对其综合品质的影响。     

乌克兰熟酸乳工艺的研究

以全脂乳粉为原料制备乌克兰熟酸乳,探讨其可行的生产工艺,采用正交试验设计方法,以感官评定为指标确定最佳工艺参数为:食用葡萄糖添加量5%,95℃下褐变3h;发酵剂0.05‰、蔗糖添加量7%、复合稳定剂添加量7%,发酵温度42℃,发酵时间8h。制得的酸乳产品呈均匀的浅褐色,口感细腻,伴有牛乳烹煮后的特殊风味。     

豌豆淀粉对脱脂乳酶凝特性及对加工低脂干酪品质的影响

为了探究豌豆淀粉作为脂肪替代物对契达干酪品质的影响,以牛乳凝乳特性为指标,分析豌豆淀粉、浓缩乳清蛋白和菊粉作为脂肪替代物的差异优势。然后将与牛乳脂肪球结构相似的豌豆淀粉(尺寸2～40μm)添加到低脂乳(脂肪含量1.5%)和脱脂乳(脂肪含量0.5%)中,制备低脂和脱脂契达干酪,探究其对牛乳凝乳特性和干酪品质的影响。再以全脂契达干酪为对照,比较分析3组干酪在成熟期组成成分、蛋白水解度、质构及感官特性的差异。结果表明,当脂肪替代物添加量为1.0%～3.0%(w/w)时,豌豆淀粉组凝乳时间(40～43 min)、凝乳强度(0.83～0.95 N)、凝乳得率(10.1%～11.9%)、乳清OD值(0.766～0.892)均显著(P0.05)优于乳清蛋白组和菊粉组。豌豆淀粉在低脂、脱脂乳中分别添加1%和2%(w/w)时,凝乳效果最佳。与全脂干酪相比,低脂和脱脂干酪的蛋白质含量分别增加2.26%、4.14%,脂肪含量分别下降15.42%、26.87%,但脱脂干酪蛋白质水解度显著低于全脂干酪(P0.05);2组干酪的W/P值、硬度、弹性、内聚性、外观色泽与全脂对照组无显著性差异(P0.05),且豌豆淀粉低脂组总体感官评分与全脂对照组差异不显著(P0.05)。     

搅拌型玉米酸乳的研制

为了强化酸乳的营养价值,从向酸乳中添加适量的纯谷物原浆角度出发,以全脂乳粉、脱脂乳粉和玉米粉为原材料,通过浓缩玉米汁添加量、果葡糖浆添加量、发酵时间、接种量等单因素试验对搅拌型玉米酸乳进行感官评定,以及采用正交试验方法确定搅拌型玉米酸乳的最佳工艺参数。最佳工艺参数为:玉米浓缩汁添加量10.0%,果葡糖浆添加量4.5%,发酵时间5.5h,接种量0.035%。     

百香果膳食纤维对凝固型益生菌酸水牛乳品质特性的影响

以百香果膳食纤维和新鲜脱脂水牛乳为原料,采用保加利亚乳杆菌(L. bulgricus)、嗜热链球菌(S. thermophilus)与干酪乳杆菌(L. casei 431)组合发酵制备百香果膳食纤维凝固型酸乳,研究了百香果膳食纤维对酸水牛乳理化性质、质构特性、流变学特性、微观结构、活菌数以及感官评价的影响。结果表明,百香果膳食纤维能够提高凝固型酸水牛乳的酸度,并在一定范围内增加酸乳的持水力。百香果膳食纤维的添加会影响酸乳的质构特性及流变特性,使酸乳更柔软、顺滑。微观结构显示,百香果膳食纤维酸水牛乳中的酪蛋白凝胶网络结构空穴更多、更开放。百香果膳食纤维可有效增殖干酪乳杆菌L. casei 431的数量,提高酸水牛乳的感官特性,添加量为1%的酸水牛乳总体可接受性最好。     

菊粉对刺云实胶-黄原胶复配体系质构和流变特性的影响

将以刺云实胶(Tara Gum)-黄原胶(Xanthan Gum)复配体系为研究对象,探究了添加菊粉(0%、5%、10%、15%、20%,w/w)对复配体系质构及流变特性的影响,并利用电镜扫描技术观察复配体系的凝胶结构。结果表明,添加15%菊粉后复配体系凝胶强度、硬度、咀嚼度、弹性、凝胶形成平均速率(SDRa)、储能模量(G')明显增大,菊粉浓度高于15%后,此六特征值被降低。采用阿伦尼乌斯方程对凝胶形成过程中的动力学参数进行拟合,决定系数均在0.90以上,具有较高的拟合度。与对照相比,添加菊粉后,活化能(Ea)明显降低,高温区与低温区表现出明显的差异。电镜扫描结果显示,添加15%的菊粉通过水合作用促进刺云实胶与黄原胶之间形成更细密、平整的网络凝胶结构,改善了复配体系的质构和流变特性。     

QuEChERS-超高效液相色谱串联质谱法测定乳粉中的双氰胺

建立了QuEChERS净化-超高效液相色谱串联三重四极杆质谱(UPLC-MS/MS)测定乳粉中双氰胺的新方法。样品用热水溶解和提取,乙腈沉淀蛋白,正己烷脱脂,QuEChERS净化,UPLC-MS/MS检测,以保留时间和特征离子对比例定性,外标法定量。探讨了脱脂乳粉、全脂乳粉、配方乳粉、酸乳粉和乳清粉5种样品的试验情况。结果表明,双氰胺在一定浓度范围内线性关系良好;方法定量限(S/N=10):配方乳粉为25μg/kg,其余4种样品均为12μg/kg;添加水平为12-250μg/k时,平均回收率在88.6-111%;相对标准偏差(n=6)为3.1-8.2%;日间精密度(n=5)为3.7-9.4%。应用本方法分析了25个样品,其中2个样品呈阳性。本方法具有前处理简单、准确、回收率高等特点,适用于不同乳粉样品中双氰胺的测定。     

水包油型乳液在无乳脂酸乳中的应用研究

以脱脂牛乳为主要原料,添加水包油型乳液油胶,经乳酸菌发酵而制成的一种以葡萄籽油代替乳脂的无乳脂酸乳。以全乳脂酸乳和脱脂酸乳为对照,通过检测酸乳样品的理化指标、质构特性、流变性以及感官指标,研究无乳脂酸乳的凝乳品质。结果表明,随着乳液油胶添加量的增加,酸乳样品的各项品质指标均有明显改善,无乳脂酸乳的凝乳品质明显优于对照样品。其中,添加4.0%乳液油胶制备的无乳脂酸乳,其模糊数学模型感官评价分值最高,为81.88分,表明其具有良好的整体接受度和开发价值。     

菊粉对减脂再制干酪功能特性的影响

针对减脂再制干酪质地偏硬、熔化性差的缺陷,拟通过添加菊粉改善减脂再制干酪的功能特性,并阐明不同聚合度菊粉对减脂再制干酪的影响。在再制干酪熔融过程中分别添加占总质量5%,10%,15%的不同聚合度菊粉替代相同比例的脂肪,制得减脂再制干酪,并测定干酪的理化指标、硬度、熔化性、流变性及微观结构。结果表明,添加低聚合度菊粉后干酪硬度显著下降(P0.05),由35.14 N降至20.58 N,其中添加10%的低聚合度菊粉干酪硬度与全脂干酪无显著性差异(P0.05);而添加高聚合度菊粉后干酪硬度显著增加(P0.05);添加菊粉后,减脂再制干酪熔化性显著改善,其中添加5%和10%菊粉的减脂再制干酪与全脂干酪相比无显著性差异(P0.05)。结论 :添加低聚合度的菊粉能显著改善减脂再制干酪的功能特性,其中添加10%低聚合度菊粉的减脂再制干酪硬度与熔化性可达到全脂再制干酪的水平。     

花生蛋白冰激凌的制作配方研究

以脱脂花生蛋白粉部分代替乳粉,研究脂肪含量较低的花生蛋白冰激凌的制作工艺。以脱脂花生蛋白粉、全脂乳粉、植脂奶油的含量为因素,通过正交试验确定制作花生蛋白冰激凌的最佳工艺配方。研究结果:在脱脂花生蛋白粉的含量为7%,全脂乳粉的含量为9%,植脂奶油的含量为6%时所制得的产品的质量最好;根据此配方制得的冰激凌感官评分为92.26分,总固形物含量为35.73%,非脂乳固体含量为6.01%,蛋白质含量为8.96%,脂肪含量为5.09%,膨胀率为83.02%。     

Effect of inulin addition on rheological and sensory properties of fat-free starch-based dairy desserts

The effect of inulin addition on the rheological and sensory properties of fat-free dairy desserts containing different starch concentrations (2.5%, 3.25% and 4%) was compared with the properties of full fat milk samples. All samples showed a thixotropic and shear-thinning flow behaviour. Hysteresis loops of inulin–skimmed milk samples were similar to those of whole milk samples without inulin. Skimmed milk samples showed lower consistency and lower shear thinning than either whole milk or inulin–skimmed milk samples. Inulin addition increased both storage modulus and complex viscosity values and decreased loss angle tangent value, except in the 4% starch sample. Adding inulin to fat-free dairy model desserts increased sweetness, thickness and creaminess. At low starch concentrations, inulin–skimmed milk desserts were perceived as sweeter, with more vanilla flavour and with the same thickness as whole milk desserts, but at 4% starch, the latter were thicker and creamier.     

Replacement of fat with long-chain inulin in a fresh cheese made from caprine milk

The aim of this study was to evaluate the effect of the replacement of fat with long-chain inulin on textural and microstructural properties of a fresh caprine milk cheese. All the samples contained the same level of total solids (about 22%, w/w) and substitution of fat with inulin at levels from 2% to 7%. Penetrometry parameters were affected by the levels of replacement of fat with inulin; samples containing inulin were characterised by lower values of compressive force, stiffness, viscosity and adhesiveness (except for the sample with 2% fat substitution). Scanning electron microscopy (SEM) images showed that the positioning of inulin within the gel interrupted the casein/fat network. In conclusion, the rheological results were dependent on the arrangement of inulin within the protein/fat network and, in particular, as shown by SEM images, on the aggregation of inulin during cheese-making.     

Inulin-enriched dairy desserts: Physicochemical and sensory aspects

The aim of this work was to study how adding inulin of different average chain lengths (long-chain, native, and short-chain inulin) at a concentration of 7.5% (wt/wt) would affect the physicochemical and sensory characteristics of starch-based dairy desserts formulated with either skim or whole milk. The results have shown that the effect of adding 7.5% inulin of different average chain length can give rise to products with different rheological behavior and different sensory characteristics. The skim milk sample with long-chain inulin and the whole milk sample without inulin showed similar flow behavior. Both samples were perceived to have the same creaminess and consistency intensity, but addition of long-chain inulin increased roughness intensity and, consequently, the sensory quality could be negatively affected. The information obtained may be of great interest in designing new products with nutritional and sensory characteristics that meet consumer demands.     

Optimising acceptability of new prebiotic low-fat milk beverages

The purpose of this work was to optimise the acceptability of two low-fat milk beverages with different types of inulin (CLR and TEX!) using Response Surface Methodology. Sixteen formulations of beverage with each inulin type were prepared, varying inulin concentration (3–8%), and sucrose concentration (0–8%). A group of 50 consumers evaluated the acceptability of the samples and tested the appropriateness of some sensory attributes intensity (colour, vanilla flavour, sweetness and thickness) using just about right scales. Response surface plots showed that formulations containing 5–8% CLR and 4–6.5% sucrose and formulations containing 4–6.5% for both TEX! inulin and sucrose were located in the optimum region. The sweetness and the thickness were the attributes that most affected the acceptability of the samples. The two low-fat samples (one for each inulin type) selected as the optimum showed no differences in acceptability (α = 0.05) between them neither when compared with a full fat control sample.     

The effect of inulin as a fat replacer on the quality of set-type low-fat yogurt manufacture

The influence of different levels of inulin on the quality of fat-free yogurt production was investigated. Inulin was added to milk containing 0.1% of milk fat to give inulin levels of 1, 2 and 3%. The experimental yogurts were compared with control yogurt produced from whole milk. The total solids content of milk was standardized to 14% by adding skim milk powder to the experimental yogurt. The chemical composition, pH, titratable acidity, whey separation, consistency, acetaldehyde and volatile fatty acidity contents were determined in the experimental yogurts after 1, 7 and 15 days. Sensory properties of the yogurts were evaluated during storage. The addition of inulin at more than 1% increased whey separation and consistency. Acetaldehyde, pH and titratable acidity were not influenced by addition of inulin. Tyrosine and volatile fatty acidity levels were negatively affected by inulin addition. With respect to the organoleptic quality of yogurt, inulin addition caused a decrease in organoleptic scores: the control yogurt had the highest score, and the lowest score was obtained in yogurt samples containing 3% of inulin. Overall, the yogurt containing 1% of inulin was similar in quality characteristics to control yogurt made with whole milk.     

Rheological and sensory properties of stirred yoghurt with inulin‐type fructans

This study concerns physicochemical and sensory analysis of stirred yoghurts, in which skim milk powder was partly replaced by different inulins. The composition of basic solutions contained 12% skim milk powder and 4% inulin, while reference yoghurts contained 16% SMP or whole milk powder. Rheological and sensory analysis showed that one‐quarter of milk powder could be substituted by long‐chain inulin in low‐fat stirred yoghurt. Short‐chain inulin and oligofructose can potentially be applied in the production of drinking yoghurt. Sensory evaluation showed that milk fat cannot be successfully substituted by inulin.     

Comparison of techniques for measuring the rheological properties of labneh (concentrated yogurt)

The effectiveness of conventional rheological dechniques (destructive) and the oscillatory dynamic test (non-destructive) for the study of the physical properties of concentrated yogurt (labneh)was studied. Six different types of labneh (control (cloth bag method), ultrafiltrated (UF) after and -before fermentation, reverse osmosis (RO) -after and -before fermentation and direct reconstitution from whole milk powder) were examined. Dynamic rheological studies revealed that labneh is a viscoelastic system in which its elastic characteristic is more dominant than its viscous properties. The elastic and viscous attributes of the control labneh were significantly different from the rest of the test samples. In general, the samples with low protein content (RO-after and -before fermentation and direct reconstitution labneh) produced weaker gel structures than their UF counterparts. The penetrometer and viscometer (destructive techniques) failed to reveal expected differences between the samples, and the results did not correlate with the oscillatory dynamic tests. In the light of these results, it could be suggested that dynamic studies are much more reliable than the destructive rheological techniques for the study of the physical properties of labneh.     

Thickness suitability of prebiotic dairy desserts: Relationship with rheological properties

In food product development it is important to know to what extent changes in formulation modifies the product, affecting its sensory properties and acceptability. Addition of polysaccharides like inulin can affect product structure in particular, modifying both rheological behaviour and perceived texture. The aim of this work was to assess to what extent rheological properties can explain the acceptability of thickness perceived by consumers in starch-based desserts. Low-fat dairy desserts were prepared varying the concentration of sucrose, flavor aroma and the fat replacer with prebiotic properties (inulin) but with fixed amounts of skimmed milk and starch. The rheological behavior was characterized and the level of sample thickness suitability was evaluated by a total of 100 consumers using a 5-point JAR scale (1 = too weak, 3 = just about right; 5 = too strong). Results indicated that flow and viscoelastic parameters varied among samples depending on inulin and sucrose concentration. According to sensory results, thickness suitability varied greatly between samples. The relationships between instrumental and sensory results are studied and discussed.     

Effect of inulin polymerization degree on various properties of synbiotic fermented milk including Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12

The effects of inulin degree of polymerization (DP) on the viabilities of Lactobacillus acidophilus La-5 and Bifidobacterium animalis Bb-12 and on some parameters of fermented milk, such as microbiological, rheological, biochemical, and sensory properties, were investigated during 30 d of storage. Samples were produced using L. acidophilus La-5 and B. animalis Bb-12, along with inulin having different DP as prebiotic, and the effects of high-DP (DP ≥ 23) and low-DP (DP ≤ 10) inulin on fermented milk, were determined. The viability of both strains increased when they were used with inulin having any DP. The addition of inulin increased the consistency index of all samples. During storage, we observed an increase in lactic and acetic acid contents of samples in which high-DP inulin was used, for both strains of bacteria. Of the combinations we tested, the sample produced with L. acidophilus La-5 and high-DP inulin demonstrated the highest rheological and sensory performance as well as the best viability of probiotics.