Rheological Properties of Tomato Concentrates as Affected by Particle Size and Methods of Concentration

Shear rate-shear stress data were obtained on tomato concentrates made from juices that were produced using finisher screen openings (FSO): 0.020, 0.027, 0.033, and 0.045 in. In general, the apparent viscosity of the concentrates at a shear rate of 100 set^-1 increased with increase in FSO. However, concentrates made from juice using a 0.027 in FSO had the highest apparent viscosity. Magnitudes of yield stress of concentrates increased in direct proportion to FSO. Apparent viscosities of concentrates made by evaporating tomato juice were lower than those obtained either by evaporating the serum or by reverse osmosis concentration of the serum.     

干燥方法对猪血清物化性质的影响

为了提高畜禽屠宰副产物畜禽血的综合利用,减少资源浪费,降低环境污染,本文以猪血为原料,探讨了不同干燥方式对畜禽血血清物化性质的影响。通过比较真空干燥、鼓风干燥和冷冻干燥对血清蛋白,血清粉的复水性、可溶性肽含量、水解度及色泽的影响,发现冷冻和鼓风干燥对血清蛋白影响较小,仅在分子量50 ku~75 ku之间出现部分聚合血清蛋白;真空干燥导致较多血清蛋白聚合,产生较多分子量大于100 ku的蛋白质;冷冻干燥血清粉的复水性优于真空和鼓风干燥,用去离子水浸泡2 h即可完全溶解,而鼓风和真空干燥血清的复水性较差,不能完全溶解;冷冻干燥血清粉的可溶性肽及水解度均显著(p0.05)高于鼓风干燥和真空干燥,鼓风干燥血清粉的可溶性肽及水解度均显著(p0.05)高于真空干燥;冷冻干燥血清粉的色差值显著(p0.05)高于鼓风和真空干燥样品。     

2种浓缩方法对柠檬汁特性影响的比较

采用界面渐进冷冻浓缩法和真空蒸发法分别对柠檬汁进行界面渐进冷冻浓缩和真空蒸发浓缩。通过对 2种浓缩液处理前后柠檬汁香气成分含量的定性定量分析 ,以及柠檬汁色差、Vc含量、电导和 pH值的比较分析 ,证明了冷冻浓缩柠檬汁明显地比真空蒸发浓缩果汁能更好地保持柠檬汁的香气成分、Vc含量和原汁的香气协调性。     

Butter making from caprine creams: effect of washing treatment on phospholipids and milk fat globule membrane proteins distribution

A washing treatment was applied to caprine cream before churning in order to improve phospholipids and MFGM protein purification from buttermilk and butter serum. Cream obtained from a first separation was diluted with water and separated a second time using pilot plant equipment. Regular and washed creams were churned to produce buttermilk and butter, from which butter serum was extracted. The washing treatment allowed a significant decrease of the casein content. As a result, the phospholipids-to-protein ratios in washed buttermilk and butter serum were markedly increased by 2.1 and 1.7-folds respectively, which represents an advantage for the production of phospholipids concentrates. However, when compared with bovine cream, lower phospholipids-to-protein ratios were observed when the washing treatment was applied to caprine cream. A higher concentration of MFGM protein and a lower retention of phospholipids during washing treatment are responsible for the lower phospholipids-to-protein ratios in buttermilk and butter serum obtained from caprine cream. The phospholipids distribution in the butter making process was similar to the one obtained from bovine regular and washed cream. Phospholipids were preferentially concentrated in the butter serum rather than the buttermilk fraction. This simple approach permitted the production of caprine and bovine butter sera extracts containing up to 180 and 240 g phospholipids/kg sera, respectively, on a dry basis.     

Flow Properties of Tomato Concentrates: Effect of Serum Viscosity and Pulp Content

Shear rate-shear stress data were obtained on tomato serum samples at 5.6, 10, 15, and 20° Brix, and on 28 concentrates prepared from the serum samples and containing different amounts of pulp: +30%, +20%, +10%, normal, ?10%, ?20%, and ?30%. Serum samples were Newtonian fluids while concentrates were shear-thinning non-Newtonian fluids. Apparent viscosities of concentrates increased linearly with pulp content expressed as weight %, volume %, or the weight ratio of pulp to serum. Apparent viscosity of the concentrates (η₁₀₀ conc) was related to the viscosity of serum (η serum) and pulp content (P) by the expression: η₁₀₀ cone =η serum + A * P ** B. The contribution of pulp content to η₁₀₀ cone was much more than that of serum. η serum was well correlated with pectin content by the expression: η serum = A₁+ B₁ (Pectin) ** C₁.     

Fumaric acid in apple juice: a potential indicator of microbial spoilage of apples used as raw material.

The effects of heat treatment (evaporation and excessive heating), and microbial contamination (Rhizopus stolonifer, Penicillium expansum and Lactobacillus plantarum) as sources of fumaric acid formation in apple juice concentrates were investigated. Fumaric acid formed in apple juice did not exceed 1.0 mg l(-1) during both commercial-scale evaporation and laboratory-scale excessive heat treatment, indicating that malic dehydration is not the primary source of fumaric acid formation. However, R. stolonifer and L. plantarum produced 18.23 +/- 0.82 and 5.39 +/- 0.31 mg l(-1) fumaric acid as determined in the raw juice obtained from contaminated apples after 5 days of incubation. The mean fumaric acid content of apple juice concentrates manufactured in 2000, 2001 and 2002 were determined as 4.9 +/- 1.9, 5.7 +/- 2.8 and 4.1 +/- 2.6 mg l(-1), respectively. The overall results suggest that the primary source of fumaric acid in apple juice concentrate is the use of apples decayed by certain microorganisms capable of producing fumaric acid.     

Scale-up of the process to obtain functional ingredients based in plasma protein concentrates from porcine blood

The feasibility of a scaled-up process to obtain two protein concentrates from porcine blood plasma, i.e. serum and albumin, for use as functional food ingredients was assessed. The process consisted of fractionating plasma proteins by salting out, concentrating and purifying fractions by means of membrane technology, and subsequently dehydrating through spray-drying. The fractionation process allowed a good isolation of the desired proteins, which were then concentrated and desalted in a tangential flow filtration (TFF) process combining ultra and diafiltration. Purification, pre-concentration and dehydration were successfully achieved. The functional properties of dehydrated serum and albumin were determined. As compared to the same hemoderivatives obtained by a lab-scale production system, serum maintained the gelling properties; albumin exhibited similar foaming properties; and both serum and albumin concentrates showed slightly improved emulsifying properties.     

双歧杆菌免疫血清的制备及性质分析

通过动物免疫方法制备了长双歧(B.longum)和两歧双歧杆菌(B.bifidum)的免疫血清，经ELISA检测，血清效价达到1：1280。用此血清和乳制品中常见细菌反应，未见明显交叉反应，这一结果为双歧杆菌发酵乳制品中双歧杆菌的血清学检测提供了参考。     

血清药理学方法评价叔丁基对苯二酚的安全性

运用血清药理学方法评价食品抗氧化剂叔丁基对苯二酚的毒性.大鼠灌胃700mg/kg叔丁基对苯二酚后,分别于0.08、0.25、0.50、24.00、48.00h采血,分离血清.以人正常肝细胞HL7702为研究对象,采用MTT法检测叔丁基对苯二酚、含叔丁基对苯二酚及其代谢物血清的细胞毒性,在倒置显微镜下观察细胞生长形态变化.结果表明:虽然高浓度的叔丁基对苯二酚会抑制细胞生长,并使细胞形态学特征改变,但叔丁基对苯二酚经体内代谢后的血清对细胞生长无显著性抑制作用.因此,在卫生标准许可范围内,叔丁基对苯二酚食用安全.     

利用DOT-ELISA筛选酵母融合子

利用动物免疫方法制备了啤酒酵母 (Saccharomycescerevisiae)和毕赤氏酵母 (Pichiapas toris)的免疫血清。将啤酒酵母和毕赤氏酵母单倍体化 ,通过原生质体融合技术促使其融合。融合后将再生菌落影印到硝酸纤维膜上分别和双亲免疫血清做Dot ELISA反应 ,呈现双阳性的即为双亲融合子。     

Athermal concentration by osmotic evaporation of roselle extract, apple and grape juices and impact on quality

Osmotic evaporation (or osmotic distillation) was carried out on roselle extract, apple and grape juices. The industrial pilot plant used had a hydrophobic, polypropylene, hollow-fiber membrane with an area of 10.2 m² and an average pore diameter of 0.2 μm. It was suitable for concentrating vegetable extracts and fruit juices, and controlled various parameters such as temperature, flow velocity, and brine concentration. The final total soluble solids (TSS) contents achieved were 660, 570, and 610 g kg⁻¹ for grape juice, apple juice, and roselle extract, respectively. Temperature and concentration of solutions significantly influenced evaporation flux, which, for roselle extract, was 1.5 kg h⁻¹ m⁻² at 610 g TSS kg⁻¹ and 45 °C. The physico-chemical, biochemical, and aromatic qualities of concentrates obtained by osmotic evaporation were much higher than those of thermal concentrates, and close to those of the initial products.

Industrial relevance

Membrane processes are increasingly used to concentrate thermo-sensitive fruit juices and plant extracts. Their capacity to operate at moderate temperatures and pressures means that their energy consumption is low, while they produce good quality concentrates. Nonetheless, the main disadvantage of baromembrane processes is their inability to reach the concentration levels standard for products of thermal evaporation because of limitations resulting from high osmotic pressure. Actually, reverse osmosis membranes and equipment limit the final concentration of fruit juices to about 25–35°Brix. Osmotic evaporation has attracted considerable interest, as it can concentrate juices to as much as 65°Brix. This process, when applied to various juices, better preserves the quality of raw materials. However, because of the geometrical limitations of commercially available membranes and modules, juices must first be clarified. To our knowledge, only a few studies on osmotic evaporation have so far been conducted at a semi-industrial scale and never with roselle extracts.     

利用抗原标记选育酵母融合子

利用动物免疫方法制备了啤酒酵母(Saccharomyees cerevisiae)和毕赤氏酵母(Pichia pastois)的免疫血清.将啤酒酵母和毕赤氏酵母单倍体化、通过原生质体融合技术促使其融合.融合后再生菌落分别和双亲免疫血清做玻片凝集反应,呈现双阳性的即为双亲融合子.     

Tocopherol composition of deodorization distillates and their antioxidative activity

During the last stage of plant oil refining, deodorization distillates containing very important biological substances such as tocopherols, sterols, terpenoids or hydrocarbons are formed as a by-products. This study aimed at evaluating the content and antioxidant capacity of tocopherol concentrates from deodorization distillates obtained after the refining of rapeseed, soybean and sunflower oil. The majority of the matrix substances were eliminated from deodorization distillates by freezing with an acetone solution at -70 degrees C. The tocopherol concentrates obtained in this way contained approximately fivefold more tocopherols than the quantity in condensates after deodorization. Antioxidant activity was investigated by observing the peroxide value at 25 degrees C and using the Oxidograph test. The test medium was lard enriched with the tocopherol concentrates of the three plant oils versus single, synthetic alpha-, gamma- and delta-tocopherols (-T), which served for comparison. In these model systems, all investigated tocopherol concentrates exhibited antioxidant capacity. Their antioxidant effect was significantly lower than that of single delta-T and gamma-T, but significantly higher than alpha-T. The results prove that natural tocopherol concentrates obtained from plant oils are valuable food antioxidants and they also increase the biological and nutritional value of food especially when administered to animal fats or food of animal origin. Tocopherol concentrates can fully replace synthetic antioxidants that have been used thus far.     

Effect of partial whey protein depletion during membrane filtration on thermal stability of milk concentrates

Membrane filtration technologies are widespread unit operations in the dairy industry, often employed to obtain ingredients with tailored processing functionalities. The objective of this work was to better understand the effect of partial removal of whey proteins by microfiltration (MF) on the heat stability of the fresh concentrates. The micellar casein concentrates were compared with control concentrates obtained using ultrafiltration (UF). Pasteurized milk was microfiltered (80 kDa polysulfone membrane) or ultrafiltered (30 kDa cellulose membrane) without diafiltration (i.e., no addition of water) to 2× and 4× concentration, based on volume reduction. The final concentrates showed no differences in pH, casein micelle size, or mineral concentration in the serum phase. The micellar casein retentates (obtained by MF) showed a 20 and 40% decrease in whey protein concentration compared with the corresponding UF milk protein concentrates for 2× and 4× concentration, respectively. The heat coagulation time decreased with increasing protein concentration, regardless of the treatment; however, MF retentates showed a higher thermal stability than the corresponding UF controls. The average diameter for casein micelles increased after heating in UF but not MF concentrates. The turbidity (measured by light scattering) increased after heating, but to a higher extent for UF retentates than for MF retentates at the same protein concentration. It was concluded that the reduced amount of whey protein in the MF retentates caused a significant increase in the heat stability compared with the corresponding UF retentates. This difference was not due to ionic composition differences or pH, but to the type and amount of complexes formed in the serum phase.     

Texture Profile Analysis of Heat-Formed Gels and Cakes Prepared with Low Cholesterol Egg Yolk Concentrates

Gels were formed by heating water dispersions of egg yolk protein concentrates of low cholesterol content, prepared from yolk by applying different lipid extraction methods. Texture profiles, obtained by applying an Instron double compression test, showed that in general, gels exhibited higher hardness and springiness and lower cohesiveness than those of the control yolk. Cakes prepared with yolk concentrates showed higher hardness and similar cohesiveness and springiness values and, with one exception, harder textures compared to control cakes, as assessed by panelists. Results were related to the differences in protein and lipid composition of yolk samples.     

Effect of processing methods and protein content of the concentrate on the properties of milk protein concentrate with 80% protein

In recent years, a large increase in the production of milk protein concentrates (MPC) has occurred. However, compared with other types of milk powders, few studies exist on the effect of key processing parameters on powder properties. In particular, it is important to understand if key processing parameters contribute to the poor solubility observed during storage of high-protein MPC powders. Ultrafiltration (UF) and diafiltration (DF) are processing steps needed to reduce the lactose content of concentrates in the preparation of MPC with a protein content of 80% (MPC80). Evaporation is sometimes used to increase the TS content of concentrates before spray drying, and some indications exist that inclusion of this processing step may affect protein properties. In this study, MPC80 powders were manufactured by 2 types of concentration methods: membrane filtration with and without the inclusion of an evaporation step. Different concentration methods could affect the mineral content of MPC powders, as soluble salts can permeate the UF membrane, whereas no mineral loss occurs during evaporation, although a shift in calcium equilibrium toward insoluble forms may occur at high protein concentration levels. It is more desirable from an energy efficiency perspective to use higher total solids in concentrates before drying, but concerns exist about whether a higher protein content would negatively affect powder functionality. Thus, MPC80 powders were also manufactured from concentrates that had 3 different final protein concentrations (19, 21, and 23%; made from 1 UF retentate using batch recirculation evaporation, a similar concentration method). After manufacture, powders were stored for 6 mo at 30°C to help understand changes in MPC80 properties that might occur during shelf-life. Solubility and foaming properties were determined at various time points during high-temperature powder storage. Inclusion of an evaporation step, as a concentration method, resulted in MPC80 that had higher ash, total calcium, and bound calcium (of rehydrated powder) contents compared to concentration with only membrane filtration. Concentration method did not significantly affect the bulk (tapped) density, solubility, or foaming properties of the MPC powders. Powder produced from concentrate with 23% protein content exhibited a higher bulk density and powder particle size than powder produced from concentrate that had 19% protein. The solubility of MPC80 powder was not influenced by the protein content of the concentrate. The solubility of all powders significantly decreased during storage at 30°C. Higher protein concentrations in concentrates resulted in rehydrated powders that had higher viscosities (even when tested at a constant protein concentration). The protein content of the concentrate did not significantly affect foaming properties. Significant changes in the mineral content are used commercially to improve MPC80 solubility. However, although the concentration method did produce a small change in the total calcium content of experimental MPC80 samples, this modification was not sufficiently large enough (<7%) to influence powder solubility.     

Comparison of composition, sensory, and volatile components of thirty-four percent whey protein and milk serum protein concentrates

The objectives of this study were to identify and compare the composition, flavor, and volatile components of serum protein concentrate (SPC) and whey protein concentrate (WPC) containing about 34% protein made from the same milk to each other and to commercial 34% WPC from 6 different factories. The SPC and WPC were manufactured in triplicate with each pair of serum and traditional whey protein manufactured from the same lot of milk. At each replication, SPC and WPC were spray dried (SD) and freeze dried (FD) to determine the effect of the heat used in spray drying on sensory properties. A trained sensory panel documented the sensory profiles of rehydrated SD or FD powders. Volatile components were extracted by solid-phase microextraction (SPME) and solvent extraction followed by solvent-assisted flavor evaporation (SAFE) with gas chromatography-mass spectrometry and gas chromatography-olfactometry. Whey protein concentrates had higher fat content, calcium, and glycomacropeptide content than SPC. Color differences (Hunter L, a, b) were not evident between SPC and WPC powders, but when rehydrated, SPC solutions were clear, whereas WPC solutions were cloudy. No consistent differences were documented in sensory profiles of SD and FD SPC and WPC. The SD WPC had low but distinct buttery (diacetyl) and cardboard flavors, whereas the SD SPC did not. Sensory profiles of both rehydrated SD products were bland and lower in overall aroma and cardboard flavor compared with the commercial WPC. Twenty-nine aroma impact compounds were identified in the SPC and WPC. Lipid and protein oxidation products were present in both products. The SPC and WPC manufactured in this study had lower total volatiles and lower concentrations of many lipid oxidation compounds when compared with commercial WPC. Our results suggest that when SPC and WPC are manufactured under controlled conditions in a similar manner from the same milk using the same ultrafiltration equipment, there are few sensory differences but distinct compositional and physical property differences that may influence functionality. Furthermore, flavor (sensory and instrumental) properties of both pilot-scale manufactured protein powders were different from commercial powders suggesting the role of other influencing factors (e.g., milk supply, processing equipment, sanitation).     

Comparison of composition and sensory properties of 80% whey protein and milk serum protein concentrates

Milk serum protein concentrates (SPC) are proteins found in cheese whey that are removed directly from milk. Because SPC are not exposed to the cheese-making process, enzymatic or chemical reactions that can lead to off-flavors are reduced. The objectives of this study were to identify and compare the composition, flavor, and volatile components of 80% protein SPC and whey protein concentrates (WPC). Each pair of 80% SPC and WPC was manufactured from the same lot of milk and this was replicated 3 times. At each replication, spray-dried product from each protein source was collected. Commercial 80% WPC were also collected from several manufacturers for sensory and volatile analyses. A trained sensory panel documented the sensory profiles of the rehydrated powders. Volatile components were extracted by solid-phase microextraction and solvent extraction followed by solvent-assisted flavor evaporation with gas chromatography-mass spectrometry and gas chromatography-olfactometry. Consumer acceptance testing of acidified 6% protein beverages made with 80% SPC and WPC produced in the pilot plant and with WPC from commercial sources was conducted. The SPC was lower in fat and had a higher pH than the WPC produced in the pilot plant or commercial WPC. Few sensory differences were found between the rehydrated SPC and WPC manufactured in this study, but their flavor profiles were distinct from the flavor of rehydrated commercial WPC. The pilot-plant WPC had higher concentrations of lipid oxidation products compared with SPC, which may be related to the higher fat content of WPC. There was a large difference in appearance between 80% SPC and WPC: solutions of SPC were clear and those of WPC were opaque. Concentrations of lipid oxidation products in commercial WPC were generally higher than those in pilot-plant SPC or WPC. Sensory profiles of the peach-flavored protein beverage included cereal, free fatty acid, and soapy flavors and bitter taste in beverages made from pilot-plant products, whereas cardboard flavors were detected in those made with commercial WPC. Consumer liking scores for the beverages made with SPC were ranked highest or equally high with beverages made with WPC for aroma, appearance, and mouthfeel, but the beverages made with SPC had lower flavor and overall liking scores compared with beverages made with 3 of the 4 WPC.     

EFFECT OF DECOLORIZATION AND LACTOSE INCORPORATION ON THE EMULSIFICATION CAPACITY OF SPRAYDRIED BLOOD PROTEIN CONCENTRATES

Blood protein concentrates were prepared from the serum and decolorized hemoglobin fractions of bovine blood. The emulsifying capacity of the concentrates was dependent on protein concentration and was not affected by spray drying. However, when the serum protein fraction was subjected to the decolorization treatment, its emulsifying capacity was reduced. Lactose, when added to the serum proteins prior to spray drying, prevented this reduction.     

Protein concentrates from pea and faba bean,obtained using waste effluents of potato processing plant or sweet whey

Protein concentrates were obtained on the laboratory scale from pea and faba bean, using waste effluents of potato, whey or water for protein extraction. The concentrates were analysed in order to determine their content of basic components and anti-nutritive substances. It was found that the concentrates obtained with waste effluents of potato were characterized by higher protein content than those obtained with whey. On the other hand, amino acid content was similar in all concentrates. Phytic phosphorus content and activity of trypsin inhibitors in the protein concentrates should not constitute any danger for animals and human beings.