蛋白质强化对搅拌型酸奶品质特性的影响

为了研究蛋白质强化对搅拌型酸奶品质特性的影响,以脱脂奶粉(SMP)和乳清浓缩蛋白-80(WPC-80)作为蛋白源,研究了强化不同种类及不同含量(2.7%、3.1%、3.5%、3.9%)的蛋白质强化对搅拌型酸奶感官品质、黏度和持水性的影响。结果表明:用SMP和WPC-80强化原料乳的蛋白质均可提高搅拌型酸奶的感官品质、黏度和持水性;比较同种蛋白源、不同蛋白质强化水平制得的搅拌型酸奶,其组织状态变化明显,风味稍有变化,色泽保持不变;酸奶的黏度和持水性都随蛋白质水平的上升而显著提高。SMP强化蛋白质含量至2.7%时,酸奶的感官品质最好;WPC-80含量则在3.5%时,酸奶的感官品质最好。同一蛋白质水平、不同强化蛋白相比较,WPC-80强化酸奶比SMP有更好的感官品质和更高的持水性,而SMP强化则得到更高的黏度值;从感官评定的黏稠度得分和测得的黏度值对比得出,搅拌型酸奶的黏度并不是越高越好,最佳黏度值在537～712mPa.s之间。实验中搅拌型酸奶的最佳蛋白强化配方为WPC-80强化蛋白质含量3.5%。     

乳固形物浓度对羊奶酸奶发酵特性的影响

研究了羊奶在杀菌条件90℃/15min、蔗糖添加量7%、菌种添加量2%条件下,乳固形物浓度对羊奶酸奶的发酵特性和后发酵特性的影响.结果表明:随着乳固形物浓度升高,酸奶发酵过程中产酸速度较快,粘度升高,持水性增强.在酸奶后发酵过程中,前期酸奶的酸度、粘度和持水性有一定程度的增加,但后期变化不大.     

乳固形物浓度对羊奶酸奶发酵特性的影响

研究了羊奶在杀菌条件90℃/15min、蔗糖添加量7%、菌种添加量2%条件下,乳固形物浓度对羊奶酸奶的发酵特性和后发酵特性的影响。结果表明:随着乳固形物浓度升高,酸奶发酵过程中产酸速度较快,粘度升高,持水性增强。在酸奶后发酵过程中,前期酸奶的酸度、粘度和持水性有一定程度的增加,但后期变化不大。      

牛乳和豆乳配比对酸奶品质特性的影响

为了探究牛乳与豆乳配比对酸奶理化性质、流变学特性、微观结构和感官特性的影响,将不同质量配比(100:0、75:25、50:50、25:75、0:100)的牛乳与豆乳混合,加入1 g/L直投式发酵剂,在43℃条件下发酵至pH=4.8,在4℃条件下贮存并进行分析.结果表明,随豆乳比例的增加,酸奶中蛋白质含量增加,脂肪含量降...     

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。     

均质与热处理对脱脂搅拌型酸奶的流变性影响

就部分工艺条件对脱脂搅拌型酸奶的流变性影响进行了研究。结果表明,随着乳固体含量的增高,酸奶的粘度增高,但当乳固体含量增加到11．5％或13．0％时,酸奶的粘度并无显著提高;乳固体为10％时,抗剪切能力最好。在蛋白质含量不变的情况下添加乳清粉,用质量分数为0．41％乳清粉代替1％脱脂奶粉制得的酸奶,其抗剪切能力明显比全部用脱脂奶粉制得的酸奶好。均质和热处理条件是影响酸奶粘稠度的重要因素。均质的最佳压力为20Mpa,温度为60℃。原料乳的最佳条件是95℃、5min,经过这样处理的原料乳酪蛋白在酸奶中可以完全凝固,乳清蛋白因充分受热而完全变性沉淀,可以使搅拌型酸奶的粘度增加,抗剪切能力也比较好。     

膳食纤维强化酸奶的流变学特性及其感官品质研究

对膳食纤维(Dietary Fiber,DF)强化酸奶的流变学特性及感官品质进行了研究.结果表明,膳食纤维不同强化量酸奶为假塑性流体,流变学特性符合冥律模型,表观黏度随膳食纤维加入量的增加而增加.触变性检验表明,膳食纤维添加量越大,触变性越小.随着贮藏时间的增加,酸奶黏度逐渐减小,而且膳食纤维添加量越多,减小的趋势越小.从健康和嗜好多方面考虑,酸奶中添加质量分数为1.0%的膳食纤维较为恰当.     

不同种类淀粉对罗非鱼鱼糜凝胶品质的影响

为了改善淡水鱼鱼糜制品的品质,以冷冻罗非鱼鱼糜为原料,分别添加4%木薯原淀粉、3种木薯变性淀粉（磷酸酯淀粉、羟丙基淀粉和乙酰化二淀粉磷酸酯）及复配木薯变性淀粉（乙酰化二淀粉磷酸酯与羟丙基淀粉质量比为3∶2）,考察淀粉添加对鱼糜凝胶质构、流变学特性、持水性及水分分布和微观结构等的影响,探讨不同种类淀粉对鱼糜凝胶品质的改善。结果表明,与对照组相比,添加5种淀粉均会显著降低罗非鱼鱼糜凝胶的白度（P<0.05）,但其凝胶强度、硬度和咀嚼性显著增大,凝胶持水性显著提高（P<0.05）,蒸煮损失率显著下降（P<0.05）,结合水含量显著增加（P<0.05）,凝胶微观结构更加均匀致密,且添加了复配木薯变性淀粉的凝胶质构特性最好,持水性最高。低场核磁共振成像和光学显微镜观察结果显示,不同种类的淀粉均能有效锁住鱼糜凝胶基质中的水分;升温过程中淀粉吸水膨胀,在鱼糜凝胶网络结构中起浓缩和填充作用;添加了复配木薯变性淀粉的鱼糜凝胶结构最致密均匀。因此,添加复配木薯变性淀粉可以有效改善罗非鱼鱼糜制品的品质,为淡水鱼鱼糜制品的开发提供了理论支撑。     

向日葵低酯果胶对搅拌型酸奶品质特性的影响

以未添加向日葵低酯果胶的酸奶为对照,研究了不同酯化度(DE)范围的低酯果胶对搅拌型酸奶性质的影响。结果表明,低酯果胶能够有效改善酸奶的持水性、黏度、质构和感官评分;加入0.08%(m/v)的酯化度范围为30%左右的低酯果胶较空白对照样品,持水性提高了9.38%;而添加等量酯化度范围为35%左右的低酯果胶后,能够有效提高酸奶的黏度至2824cP,且相比其他低酯果胶,其对应酸奶的感官评分最高。实际生产中可根据产品需求,选择30%～35%酯化度的向日葵低酯果胶对酸奶进行结构状态和感官风味的改善。     

魔芋葡甘聚糖在搅拌型酸奶中的应用

向搅拌型酸奶中添加不同质量分数的魔芋葡甘聚糖(Konjac Glucomannan,KGM),从持水性、乳清析出量、pH、酸度、凝胶强度和流变性等方面探究KGM添加量对搅拌型酸奶品质的影响.结果表明,当添加的KGM质量分数从0.01％增加至0.1％时,搅拌型酸奶的持水性、酸度、凝胶强度、屈服应力不断上升,乳清析出量、p...     

Individual and sequential effects of stirring,smoothing, and cooling on the rheological properties of nonfat yogurts stirred with a technical scale unit

Few studies have considered the impact of unit operations during stirred yogurt manufacture because their operational sequence is difficult to replicate at the laboratory scale. The aim of this study was to investigate the individual and sequential effects of stirring in the yogurt vat, smoothing, and cooling on the rheological properties of yogurts, using a technical scale unit simulating some industrial conditions. The yogurts were prepared from a milk mixture that was standardized to contain 14% total solids, 0% fat, and 4% protein, and then homogenized, heated (94.5°C, 5 min), and inoculated at 41°C with the same thermophilic lactic starter. The operating parameters under investigation were 2 stirring durations in the yogurt vat (5 or 10 min), 2 cooling systems (plate or tubular heat exchanger), and 2 smoothing temperatures (38°C for smoothing before cooling; 20°C for smoothing after cooling). Sampling valves were installed at critical points on the technical scale unit so that the effect of each operation on the properties of stirred yogurt could be quantified individually. Syneresis, apparent viscosity, firmness, and consistency were analyzed after 1 d of storage at 4°C. In general, as the yogurts moved through the technical scale unit, the properties of the yogurts (evaluated after 1 d) changed: viscosity increased but syneresis, firmness, and consistency decreased. The individual effects of the operations showed that smoothing and cooling, compared with stirring duration, made the greatest contribution in terms of modifying yogurt properties. The stirring parameters (5 or 10 min) had similar effects on the yogurts. The use of a plate heat exchanger promoted a decrease in syneresis, whereas a tubular heat exchanger had a greater effect in terms of increasing firmness and consistency. The type of cooling system had no effect on stirred yogurt viscosity. Smoothing at 38°C had a greater effect on the increase in firmness, whereas smoothing at 20°C contributed more to a decrease in syneresis and increases in viscosity and consistency. This study confirms that each unit operation has a defined effect on the rheological properties of a nonfat stirred yogurt, which also depends on the operation sequence.     

Effect of protein concentration on the properties and structure of concentrated yogurts

Concentrated yogurts were produced by traditional (control), direct reconstitution, ultrafiltration and reverse osmosis techniques. The membrane techniques were applied either before or soon after incubation. The physical properties of the samples were monitored using a penetrometer (set yogurt) and viscometer (stirred yogurt), and the results indicated that different manufacturing techniques led to differences in the rheology of the concentrated yogurts. As expected, samples with high protein contents had greater gel strengths. Also, the concentration techniques caused large differences between the samples, even at the same protein level. The rheological properties correlated well with the microstructure as monitored by confocal laser scanning microscopy. In general, larger compartments in the network were associated with a weaker structure.     

Influence of proteins on the perception of flavored stirred yogurts

Among yogurt dairy components, protein type is known to modify the texture of the products and the volatility of odorous volatile organic compounds. The aim of this study was to investigate the impact of 3 protein ratios (caseinate to total protein) on the sensory properties of 4% fat, strawberry-flavored stirred yogurts. A sensory methodology study was therefore investigated to choose the most efficient method in terms of sensitivity, quantification, and ease with which the panel could distinguish slight differences in olfactory property between the yogurts. Three kinds of product presentation procedures were compared: a monadic presentation, a comparative presentation, and a comparative presentation with a reference. The results showed that the 3 presentation methods emphasized some important texture differences between the yogurts in the same way. However, the comparative procedure with a reference was the only one to reveal clear olfactory property differences between the yogurts. The main effect of protein ratio variation in yogurt concerned the texture properties, which greatly differed between the 3 yogurts and was confirmed by complex viscosity measurements. Olfactory differences between the yogurts were more subtle. Overall, the flavor intensity and the fruity notes were less intense in the yogurts with the high caseinate ratio than in those with the low ratio. This result was in agreement with the physicochemical measurements, which showed a higher retention of a large majority of aroma compounds of the strawberry flavor in the yogurts with a high caseinate ratio.     

Smoothing temperature and ratio of casein to whey protein: Two tools to improve nonfat stirred yogurt properties

Consumers are not always ready to compromise on the loss of texture and increased syneresis that nonfat stirred yogurts display compared with yogurts that contain fat. In this study, we investigated milk protein composition and smoothing temperature as a means to control nonfat yogurt microstructure, textural properties, and syneresis. Yogurts were prepared with different ratios of casein to whey protein (R1.5, R2.8, and R3.9). Yogurts were pumped through a smoothing pilot system comprising a plate heat exchanger set at 15, 20, or 25°C and then stored at 4°C until analysis (d 1, 9, and 23). Yogurt particle size and firmness were measured. Yogurt syneresis and water mobility were determined, respectively, by centrifugation and time domain low-frequency proton nuclear magnetic resonance (¹H-LF-NMR). Increasing the smoothing temperature increased gel firmness and microgel (dense protein aggregates) sizes independently of the whey protein content. Also, yogurt microgel sizes changed with storage time, but the evolution pattern depended on protein ratio. Yogurt R1.5 showed the largest particles, and their sizes increased with storage, whereas R2.8 and R3.9 had smaller microgels, and R3.9 did not show any increase in microgel size during storage. Micrographs showed a heterogeneous gel with the empty area occupied by serum for R1.5, whereas R2.8 and R3.9 showed fewer serum zones and a more disrupted gel embedding microgels. Induced syneresis reduced with greater whey protein content and time of storage. This is in agreement with ¹H-LF-NMR showing less bulk water mobility with increasing whey protein content during storage. However, ¹H-LF-RMN revealed higher values of spontaneous serum separation during storage for R1.5 and R3.9 yogurts, whereas these were lower and stable for R2.8 yogurt. Microgels play an important structural role in yogurt textural attributes, and their characteristics are modulated by whey protein content and smoothing temperature. Optimization of these parameters may help improve nonfat stirred dairy gel.     

Chemical properties and sensory quality of ice cream fortified with fish protein

BACKGROUND: Fish protein powder is a functional ingredient that can be used for enhancing the nutritional value of food products. In this study the effect of fortification with different levels of fish protein powder (FP) on chemical properties and sensory quality of Persian ice cream with 0, 30 and 50 g kg^?1 FP during storage at ? 18 °C for 4 months was investigated. RESULTS: Ice creams fortified with 50 and 30 g kg^?1 FP had significantly higher protein and solid‐non‐fat content than ice cream with 0% FP or 83, 69 and 51 g kg^?1 protein and 215, 204 and 181 g kg^?1 solid non‐fat, respectively. All products had the same levels of fat, lactose, acidity and pH. They had similar sensory quality after production except for colour, but sensory properties of fortified samples changed significantly after 2 months of storage. Colour faded, cohesiveness decreased, sandiness/coarseness increased, sweetness decreased and fish flavour and off‐odour increased. The control ice cream scored highest for additives odour and flavour. CONCLUSION: Development of ice cream fortified with fish protein powder could be an effective way to enhance nutritional and functional value of ice cream. But studies on storage stability, consumers' acceptance and attitudes are recommended if companies are planning to do so. Copyright © 2011 Society of Chemical Industry     

谷氨酰胺转胺酶对搅拌型酸奶品质的影响

因为谷氨酰胺转胺酶对乳蛋白有交联作用,所以在酸奶制作中加入谷氨酰胺转胺酶可以提高酸奶的品质,将0.2g/L牛乳的谷氨酰胺转胺酶使用不同的添加方法(对酶灭活和不灭活)应用到酸奶制作中,通过酸奶硬度、持水力、流变特性、乳酸菌等指标的变化及综合感官评价,评定谷氨酰胺转胺酶的最适添加方法。结果表明两种不同的酶添加方法都可以减弱酸奶后酸化,提高酸奶硬度、持水力和剪切应力。TGase酶与发酵剂同时加入显著提高了酸奶的理化特性(p<0.05),硬度在第21d达到最大,与对照组相比提高8.48g,持水力随贮存时间的延长,不断增大,增幅为5.41%。在贮存后期TGase酶活力减弱,对酸奶的质构无不良影响,而且这种方法不需要额外的酶反应时间,热处理工序及设备,符合实际生产的需求。      

Studies on physicochemical and antioxidant properties of strawberry polyphenol extract–fortified stirred Dahi

The addition of bioactive polyphenolic compounds to dairy products is linked to improve their antioxidant potential. The aim of the present investigation was to evaluate the effect of strawberry polyphenol on physicochemical properties, total phenolic and antioxidant activity of stirred dahi. Strawberry polyphenol extract was used to fortify stirred dahi (0.5 mg/mL). This fortification resulted in a sevenfold increase in the antioxidant activity of polyphenol‐enriched stirred dahi, while pH, acidity, water‐holding capacity and viscosity remained comparable with the control. Sensory analysis indicated that the product was acceptable up to 2 weeks when stored at 7–8 °C with no significant difference (P > 0.05) in the antioxidant activity and total phenolic content.     

乳清浓缩蛋白对搅拌型酸奶品质特性影响的研究

研究了以全脂奶粉和乳清浓缩蛋白（WPC-3503）为原料，按照全脂奶粉：乳清浓缩蛋白为100：0，90：10，80：20，70：30的质量配比生产乳固形物含量为12％的酸奶，对含有不同乳清蛋白比例的酸奶在贮藏过程中理化特性、乳酸菌总数的变化以及感官特性进行了比较分析。结果表明，WPC-3503代替10％-20％全脂奶粉生产酸奶时，在贮藏过程中可减缓pH值及酸度的变化速度，提高酸奶的黏度和保水率，改善感官特性，但对乳酸菌总数无明显的影响。