Effects of fermentation conditions and homogenization pressure on the rheological properties of Kefir

In this study, the effects of fermentation conditions (temperature and time) as well as homogenization pressure on the rheology and EPS production in Kefir made from bovine whole milk were investigated. Results showed that the rheological characteristics and EPS production are affected significantly (p < 0.05) by the fermentation temperature but not by the incubation time. Furthermore, the homogenization pressure was found to influence significantly (p < 0.05) the rheology but not the production of EPS in Kefir.     

Effect of high-pressure homogenization on microstructure and rheological properties of alkali-treated high-amylose maize starch

The effect of high-pressure homogenization (HPH) on the microstructure, rheological properties, paste clarity, as well as gel retrogradation behavior of alkali-gelatinized high-amylose maize starch (HMS) was investigated. The alkali-treated HMS pastes were subjected to HPH at homogenizing pressures of 25, 50, 75, 100, and 125 MPa. After HPH treatment, the uniformity in the microstructure of HMS pastes was greatly increased. At homogenizing pressures greater than 100 MPa, starch ghost particles were found to completely disappear. The apparent viscosity of the HMS pastes was found to decrease significantly due to the application of HPH. The paste clarity of the HMS pastes increased when HPH treatment was applied. After storing at 4 °C for 7 days, HMS pastes homogenized at 50 and 100 MPa displayed weaker viscoelastic behavior than their corresponding unhomogenized pastes. This indicated that HPH treatment is capable of inhibiting starch retrogradation in gels.     

Changes in the physicochemical,microstructural and rheological properties of traditional Kope cheese during ripening

The effect of ripening time on the microstructural, physicochemical and rheological characteristics of traditional Kope cheese ripened in clay pots was investigated. The moisture content, pH and total nitrogen (TN)/dry matter (DM) of the cheese decreased, and DM, fat in DM and water‐soluble nitrogen/TN increased during this period. Storage and loss moduli increased, while loss tangent decreased; as a result, the elasticity characteristics were greater than the viscous characteristics of the samples. Microstructure images showed that the size of pores and casein network density increased significantly during ripening and, after 90 days, the structure of many pores became very similar to each other.     

Effect of some hydrocolloids on the rheological properties of different formulated ketchups

Five different hydrocolloids (tragacanth gum, guar gum, carboxy methyl cellulose, xanthan gum and locust bean gum) were added, at levels of 0, 0.5, and 1 g/100 g (w/w), respectively, to three different formulated ketchups which were processed from cold-break tomato paste dilutions, having total soluble solid (TSS) contents of 7.5, 10, and 12.5 g/100 g (w/w), in sequence, and the effect of these hydrocolloids on the rheological properties of tomato ketchups was investigated using a viscometer with smooth surface wide-gap coaxial cylinders. All hydrocolloids increased the consistency of the tested samples; however, guar gum and locust bean gum caused the maximum increase, followed by xanthan gum, tragacanth gum and carboxy methyl cellulose (CMC). Both the ketchup formulation and the hydrocolloid concentration were found to affect the consistency of ketchups. The highest consistency index was obtained by processing dilutions with a TSS content of 12.5%, and the addition of hydrocolloids at the level of 1%. The fluidity of the ketchups decreased with both the addition of all hydrocolloids and the increase in hydrocolloids concentration. Furthermore, the fluidity of the ketchups was also affected by ketchup formulation, and it was found to be the lowest for the samples prepared from the tomato paste dilutions having a TSS content of 12.5%.     

乳成分对酸奶凝胶微观结构和流变学性质的影响

酸奶凝胶的许多宏观的物理特性与其微观结构和流变学性质密切相关。从酸奶的微结构、流变学性质和质地等方面综述了乳脂肪、蛋白质及调节酪蛋白和乳清蛋白比例对酸奶凝胶的影响。     

酸度和钙质量分数对复原乳酶凝胶质地特性的影响

考察了不同酸度、钙质量分数调节后复原乳酶凝胶的质地特性,并对其质地变量进行了主成分分析。结果表明,不同工艺处理样品间的差异可以清晰地表现在两个新变量中。酸度、钙质量分数调整可对凝胶的表观黏度和持水力产生很大影响。此外,通过对照分析可以发现,不同前处理的复原乳样品具有与原料乳相近的凝胶特性。     

Effect of homogenization conditions on physicochemical properties of chitosan-based film-forming dispersions and films

Film-forming dispersions (FFD) based on high molecular weight chitosan (CH) alone or in combination with oleic acid (OA) were prepared under different homogenization conditions (rotor-stator or rotor stator together with microfluidization at different pressures). Film-forming dispersions (FFD) were characterized in terms of particle size distribution, rheological properties, distribution and ζ-potential. In order to study the impact of the properties of the FFD on the casted films, the water vapour permeability, mechanical properties and microstructure of the dry films were evaluated. Results showed that microfluidization promoted significant changes in the size and surface charge of the FFD particles, which in turn had an impact on the rheological properties of the FFD. The changes were more marked with the increase in microfluidization pressure. As regards film properties, the higher the microfluidization pressure in the FFD, the lower the water vapour permeability values and the stiffer the CH-OA composite films. These results were explained by film microstructure, which was observed by SEM.     

Impact of citric acid on the tenderness,microstructure and oxidative stability of beef muscle

Acidification of meat can improve texture however it also increases susceptibility to lipid oxidation. The effect of injection and marination of citric acid to acidify and sodium carbonate or sodium tri-polyphosphate to increase pH of beef on tenderness, microstructure and oxidative stability was determined. Water-holding capacity and tenderness of beef semitendinosus muscle increased significantly at pH 3.52 upon addition of citric acid and returned to the level of untreated sample after pH was increased (pH ∼5.26) by sodium tri-polyphosphate. The microstructure of the muscle was lost upon acidification but reformed upon increasing muscle pH. Lipid oxidation was inhibited in cooked beef blocks and ground muscle acidified with citric acid. Lipid oxidation was also inhibited in citric acid acidified beef that was readjustment to pH values equal to or greater than the raw beef muscle with sodium tri-polyphosphate or sodium carbonate. In addition, citric acid that was adjusted to the pH of the raw beef so that it did not alter the pH of the beef also inhibited lipid oxidation. These results indicate that citric acid and not sodium tri-polyphosphate or pH adjustment was responsible for inhibiting lipid oxidation in beef. These results suggest that the best acid marination technique for beef would be citric acid since it is effective at both improving texture and inhibiting lipid oxidation.     

The Effect of Ageing at a Low Temperature on the Rheological Properties of Kahramanmaras-Type Ice Cream Mix

The aim of this article was to investigate the effect of ageing on the rheological parameters of ice cream mix. We prepared the model mix in accordance with the traditional Kahramanmaras-type ice-cream manufacturing method. The apparent viscosity (η_a) of the samples was measured as a function of shear rate, and the Power Law model was used to determine flow behavior (n) and consistency indices (K). The η_a of sample was significantly affected from ageing time as it increased up to 24 hours then decreased. The values of n and K of the samples ranged in 0.336 to 0.359 and 3719.72 – 4328.73 mPa.sⁿ, respectively. After 24 hours of ageing, K and η_a of the mix reached the highest, while the n reached the lowest values. These results suggested that 24 hours of waiting would be a proper ageing time for the ice cream mix. It could be recommended that ice cream mix may be aged at 0°C for about 24 hours before proceeding to the freezing step of ice cream manufacturing.     

Investigation of changes in formulation and processing parameters on the physical properties of cocoa butter emulsions

The aim of this work was to understand the physical characteristics of cocoa butter water in oil emulsions made using a process typically used for margarine production (a scraped surface heat exchanger and pin stirrer). Processing parameters were manipulated, and the effect of aqueous phase volume, polyglycerol polyricinoleate (PGPR) concentration, and the addition of a hydrocolloid to the aqueous phase were investigated. This process allowed small droplets to be formed (3–5 μm). Tempering could also be mimicked, with the temperature of the units affecting the polymorphic form of cocoa butter produced. Sintered crystalline shells were observed at the oil/water droplet interface, acting as Pickering particles. This work highlights the potential for the use of cocoa butter emulsions to give fat reduction in chocolate, using a one step process to achieve emulsification and to mimic tempering.     

Effect of using transglutaminase on physical,chemical and sensory properties of set-type yoghurt

This study was conducted in order to evaluate the effects of transglutaminase (TGase) addition on some properties of set-type yoghurts such as titratable acidity, lactic acid, tyrosine, viscosity, gel firmness, syneresis, aroma compounds, sensory analysis, and micro-structural properties. The enzyme was added to yoghurt-milk at different production steps (after homogenization, after pasteurization and together with starter culture addition) and two different incubation times (10 min and 1 h) were used. Five TGase treated yoghurt samples and control sample were analyzed on 1st, 10th, and 20th days of storage. TGase addition did not cause significant changes on chemical properties of yoghurts. However, enzyme addition after pasteurization increased the gel strength and decreased the syneresis. Results of electron microscope showed that enzyme addition led proteins to be distributed more evenly in gel network due to the formation of cross-links between proteins.     

Effect of guar gum content on some physical and nutritional properties of extruded products

The effect of guar gum (0-10%) added to flour (maize, potato, rice, and wheat) prior to extrusion on the microstructure, physical properties (texture, expansion, density, pasting) and nutritional properties (starch digestibility) was investigated. The inclusion of guar gum did not decrease starch digestibility; rather, at 10% guar gum rapidly digestible starch increased by 24%, 15%, 25% and 43%, in maize, potato, rice and wheat flour-based products, respectively. In general, increases in starch digestibility appear to be related to the weaker microstructure (i.e., lower textural hardness), larger matrix surface area, and lower viscosity (pasting properties) of extrudates containing guar gum. These results suggest that microstructural changes affect the starch digestibility of extrudates; nevertheless, probably other factors such as particle size during digestion may also play an important role.     

Effect of milk homogenisation and foaming temperature on properties and microstructure of foams from pasteurised whole milk

Differently homogenised and HTST-heated milk (3.5% fat) was foamed at temperatures between 4 and 60 °C. Foaming was achieved by air injection through fritted glass. Initial foam density, drainage and corresponding bubble size were analysed. Transmission electron microscopic (TEM) images completed the study. The studies showed that whole milk was better foamable between 50 and 60 °C than at lower temperatures. This was mainly due to the completely liquid milk fat and the increased protein adsorption at the air-serum interface. The resulting bubbles of these two foams maintained their spherical shape also for 20 min of draining. However, the average bubble diameter and the drainage mass in relation to the initial foam mass increased from about 20 g/100 g after 1 min to about 80 g/100 g after 20 min. It was surprising to learn that milk homogenisation and corresponding fat globule size had only marginal effect on foam formation and stability. TEM images suggested that the air-serum interface consisted mainly of protein monomers and oligomers, while casein micelles were not directly adsorbed. The membrane of the homogenised fat globules was destroyed near the interface and coalesced liquid fat formed a restricted film on the bubble that was obviously of minor importance for the foam properties.     

Effect of laccase and transglutaminase on the textural and water-binding properties of cooked chicken breast meat gels

The effects of laccase and transglutaminase (TG) on the firmness and weight loss of cooked chicken meat homogenate gels were investigated at laboratory scale. The salt, trisodium pyrophosphate and meat contents were also used as variables. Laccase decreased firmness and increased weight loss of phosphate-free, low-meat (65%) and low-salt (1%) gels, although it modified myosin and troponin T and reacted with isolated myofibrils. By applying both low-salt (1%) and low-phosphate (0.17%) amounts, gel firmness decreased and weight loss increased (p<0.05) greatly. A high dosage of TG significantly improved (p<0.05) the strength of phosphate-free, low-meat and low-salt homogenate gels compared to the corresponding no-enzyme controls. TG improved gel firmness of the low-meat homogenate to the level of the homogenate containing 75% meat. Weight loss was increased significantly (p<0.05) in all cases when the high-TG dosage was used. Enzymes were not capable of improving either texture or water-holding capacity in the low-salt–low-phosphate system. The firmness and cooking loss of the chicken meat products containing different amounts of meat, salt and TG were investigated at pilot scale. Under the conditions and dosages used, TG was capable of improving (p<0.05) firmness of the products without a significant reduction in water-holding capacity.     

Effect of harvesting hour on some physical and mechanical properties of Rosa damascena Mill

BACKGROUND: Mechanization of Rosa damascena flower harvest is limited because of the asynchronous flowering period, the necessity for the harvest operation to take place in the early hour of the morning, and a lack of knowledge regarding the physical–mechanical properties of R. damascena. This study investigated the effect of harvesting hour on some physical–mechanical properties of R. damascena. RESULTS: The terminal velocity of the rose flower ranged from 4.00 to 2.38 m s^?1. The highest picking force was found to be 6.29 N for the harvesting hour of 06:00 am. Tear forces of petal changed from 1.54 to 0.97 N for the harvesting hour of 06:00 am and 12:00 pm, respectively. The tension force of pedicel varied between 8.25 and 7.76 N. The weight of the rose flower was measured as an average of 1.61 and 1.50 g at 06:00 am and 12:00 pm, respectively. Horizontal and vertical projection areas of rose flowers were positively correlated with harvesting hour, with an R² of 0.97 and 0.75, respectively. Results showed that there was a minor loss in colour for both inner and outer surfaces of petals. CONCLUSION: The results of physical–mechanical properties of R. damascena obtained from this study should be considered for the operation of flower harvest mechanization. Copyright © 2011 Society of Chemical Industry     

Effect of amylose/amylopectin ratio and extent of processing on the physical properties of expanded maize starches

Low-density expanded starchy products are often desirable, particularly in the snack food industry. Levels of shear and amylose are often deemed crucial factors for expansion. In this study, maize starches containing low (waxy), normal and high levels of amylose were compared after processing. Low shear processing used a popping head (similar to a rice-cake machine), while high shear (~450 kJ kg⁻¹) samples (pellets and directly expanded) were created using twin-screw thermomechanical extrusion. Native starches and ground extruded materials (<106 µm) were popped using the same conditions (230 °C, 4 s, water content 12% wwb). All samples tested created fused aerated cakes, which had little or no remaining crystallinity, except for the directly popped waxy sample, which retained ~17% of its original crystallinity. Water absorbances and solubilities were influenced greatly by the starch source and marginally by the amount of processing. On processing, waxy samples showed increased solubility while those with normal amylose content had greater absorption. The densities of all the popped samples were similar despite marked differences in shear regime history and the major variations in the amylose and amylopectin ratios. These results challenge the expected relationships between shear and different starches’ potential to expand.     

Effect of food ingredients and selected lipids on the physical properties of extruded edible films/casings

Films/casings produced using pectin (PN) and gelatin/sodium alginate blends (GSAB) containing 2.5 and 5% added corn oil (CO) or olive oil (OO) and non‐oil containing were manufactured using extrusion technology. Films/casings formed from PN and GSAB had great difference in properties of tensile strength, elongation, Young's modulus and puncture resistance. Quality and stability of films/casings were greatly enhanced on addition of oils. However, an oil addition of 2.5% was identified as optimal while 5% decreased the final films/casings quality. Oil addition increased (P < 0.05) films/casings thicknesses. Oil addition also decreased (P < 0.05) tensile strength, puncture resistance, Young's modulus and tear resistance of films/casings but increased their elongation properties, with the exception of converse effect of 2.5% CO on two films/casings. Olive oil and CO both reduced (P < 0.05) water vapour transfer rate (WVTR) of films/casings. However, no significant difference between films using different concentrations of oil was observed with respect to WVTR.     

染色温度与时间对羊绒纤维机械性能的影响

在山羊绒纤维的染色过程中,温度与时间是两项重要的工艺参数,探讨不同染色温度、保温时间对染色后色绒断裂强力、断裂伸长率和卷曲率的影响,结果表明:总体来看,随染色温度上升或染色时间延长,断裂强力、断裂伸长率和卷曲率都呈下降趋势.其中,断裂强力和断裂伸长率受染色时间影响小,但随温度升高均明显降低,85℃以上时,下降幅度明显增大；在染色时间为15 min和30 min时,卷曲率随温度上升至70℃以上受温度影响较小并逐步趋于平衡,但染色时间为45 min和60 min时,卷曲率曲线在65℃和90℃处出现明显下降的折点.     

染色碱洗工艺对Optim羊毛纤维卷曲性能的影响

拉细羊毛纤维是经物理拉伸改性变细的羊毛纤维,原有的卷曲性能发生了改变.文章探讨在染色皂洗工艺从染色温度50～95℃,保温时间5～50 min,纯碱质量浓度2.O～2.8 g/L时,分别测试皂洗后色绒的卷曲率变化规律.测试结果表明:在相同纯碱质量浓度下,随着温度升高,在80℃之前,卷曲率没有明显变化,当温度高于80℃以后,卷曲率开始快速减小.在相同碱洗温度下,纯碱质量浓度的变化对卷曲率变化没有明显规律,但随纯碱质量浓度提高,卷曲率总体上随之减小.在相同纯碱质量浓度下,碱洗时间35 min以内,变化不明显,但之后随着碱洗时间的延长,卷曲率缓慢地减小.在相同碱洗时间里,碱洗纯碱质量浓度增加,纤维卷曲率反而减小.