挤压蒸煮在乳制品中的应用

介绍了挤压蒸煮在乳制品中的应用；论述了挤压蒸煮的优越性及其在干酪，酪蛋白酸盐，脂肪类似物的制备等方面的广阔应用前景及其重要意义。     

挤压蒸煮技术在变性淀粉生产中的应用

主要阐述了挤压加工原理,以及用挤压机作反应器生产氧化、酯化、交联和醚化等多种类型的变性淀粉,并对其相关性质进行了简要分析。认为挤压蒸煮技术是快速、连续生产多种变性淀粉的一种经济可行的方法。     

Continuous emulsification and gelation of dairy ingredients by HTST extrusion cooking: production of processed cheeses

Processed cheese was prepared batchwise and by extrusion cooking. The cheddar-based cheese mix contained varying amounts of polyphosphate ions, rework, lipids, water and/or non cheese proteins. The extrusion conditions (barrel temperatures, screw speed and screw profile) were also varied. The texture, structure and colour characteristics of batch and extrusion-processed cheeses were evaluated using penetrometry, scanning electron microscopy and reflectance measurements. The degree of fat emulsification was assessed and the proportion of casein nitrogen sedimentable by ultracentrifugation was determined, as a means of following micellar disruption plus casein restructuring due to extrusion and to the additional creaming step. Results indicate that extrusion cooking can be used to continuously mix, melt, emulsify and gel the cheese mix constituents, and that processed cheeses or cheese analogues of varying texture (spreadable to sliceable) can be obtained, with a mean residence time in the extruder of about 100 seconds.     

改良挤压技术制备低蛋白质构米的研究

以粳米淀粉为原料,使用改良挤压技术制备低蛋白质构米,利用响应面分析法考察加工参数如物料含水率、螺杆转速和机筒温度的变化对低蛋白米质构特性的影响,并且以粳米的质构指标为参考指标,优化低蛋白质构米的制备工艺。结果表明,最优工艺参数为物料含水率35%,螺杆转速30r/min,机筒温度(糊化区温度)120℃,该工艺条件下,低蛋白质构米的硬度为(9 122±244)g,黏性为(-983±49)g.s,弹性为0.67±0.05,接近粳米的质构特性(硬度为(8 996±196)g,黏性为(-627±41)g.s,弹性为0.62±0.03)。同时,与粳米相比,其蛋白质含量非常低,为0.43%±0.01%,而且外观和色泽接近市售粳米,米粒完整,颜色均一,圆润光滑,轮廓分明,米质结构紧密。     

热塑挤压蒸煮处理技术对大豆蛋白基本特性的影响

利用双轴挤压蒸煮处理技术对大豆蛋白进行处理,从质构特性、功能特性及营养特性等三方面对挤出物的组织化效果进行研究。以三个挤压操作参数供水率、螺杆转速和腔体温度为输入参数,挤出物的最大剪切力、复水率、持水率和蛋白质体外消化率为响应参数,探索挤压蒸煮系统操作参数对大豆蛋白质基本特性的影响规律,统计分析表明,三个挤压操作参数与响应参数之间存在显著的相关关系,所得拟合回归模型具有较高的可信度。挤压蒸煮处理操作参数对大豆蛋白的组织化效果有明显影响。     

Thiamine destruction during extrusion cooking as an indicator of the intensity of thermal processing

Assessment of the intensity of high temperature-short time (HTST) extrusion cooking was studied by measuring the extent X_A of thiamine destruction. Small quantities of thiamine hydrochloride (0.1–0.7 g per 100 g) were mixed with wheat flour (containing ∼ 14% water) prior to extrusion experiments. Results indicate that thiamine destruction follows an apparent first-order reaction and that the rate constant K of destruction, calculated from near isothermal extrusion experiments at 133, 142 or 152°C (product temperature), follows an Arrhenius relationship with an activation energy of 49.9 kJ/mol.
K values were calculated from experimental determination of X_A and of the residence time distribution (RTD) in the effective heating zone of the extruder.
The influence of product temperature (just before the die), water content during extrusion and speed of screw rotation on the overall K (for non-isothermal extrusion experiments) was determined and analysed by multiple regression. Results show that thiamine destruction X_A can be predicted by means of a linear mathematical model.
Each experimental X_A value can be used, in combination with Arrhenius equation constants and RTD, to express a given extrusion process in terms of equivalent isothermal temperature and equivalent plug flow residence time.     

Effect of grain hardness on bioavailability of iron in wheat as determined using the coupled invitro digestion/Caco-2 model

The impact of grain hardness on iron bioavailability from a set of wheat genotypes with varying hardness indices was determined. This may help us to consider grain hardness as an important parameter along with other established parameters for selecting food crops for future biofortification programs to combat iron deficiency linked to global health problem. The bioavailability and dialysability of iron were determined using the coupled in vitro digestion/Caco-2 model. The grain hardness and its molecular basis along with grain iron, phytate and inorganic phosphorous (Pi) contents were also evaluated. The data indicated that iron concentration in the genotypes ranged from 21 to 50 μg/g of dry matter. The hardness indices varied from as low as 28 for the derivative BTC17 to as high as 92 for the landrace IITR 26, almost similar to that of WL711, a wild type cultivar considered as control in this study. Low variability was however observed for the phytate and Pi contents. A significant negative correlation was observed between grain hardness vs. dialysability (r = −0.73) and bioavailability (r = −0.75) of iron. The results suggest that the hardness index which profoundly affects milling process, particle size of flour, milling yield and end-use also influences dialysability and bioavailability of iron from wheat.     

干燥温度对改良挤压法制备的全谷物质构米品质的影响

研究干燥温度(40～80℃)对改良挤压法制备的全谷物质构米的营养特性、食用品质和热力学特性的影响。结果表明:干燥温度在40～80℃,全谷物质构米的粗脂肪和脂肪酸含量随温度升高而降低,对其他营养素无明显影响;当干燥温度低于50℃时,全谷物质构大米样品具有易消解、米饭较软、黏弹性大、口感较好的食味品质;同时,DSC的试验数据表明干燥温度低于50℃时,全谷物质构米具有起始糊化温度略低,糊化时间更短,糊化焓更小的热力学特性。     

Influence of food processing on iron availability in vitro from extruded maize-based snack foods

Samples of an extruded maize-based snack food taken at various points during manufacture were digested in vitro under simulated physiological conditions. The proportion of iron diffusing across a semi-permeable membrane was used as an index of bioavailability. Iron diffusibility increased from less than 3 % in raw whole maize to over 20 % in the finished product. Four processing stages were found to be responsible for this enhancement: (I) refining of raw maize, (2) product formulation, (3) extrusion cooking, (4) addition of flavourings. The extrusion cooking process itself was responsible for only a small part of the increase in iron diffusibility. There was a reduction in iron content due to refining, but a small increase in iron content due to product formulation and extrusion cooking. The various factors associated with each stage of snack food manufacture are discussed in relation to their potential influence on iron availability.     

Effect of dietary mineral phosphorus and phytate on in situ ruminal phytate disappearance from different concentrates in dairy cows

The first objective of this study was to determine the influence of dietary composition on the in situ disappearance of phytate (InsP₆) from wheat, corn, soybean meal, and rapeseed meal [solvent-extracted, without (RSM) or with (hRSM) heat treatment] in the rumen of dairy cows. The second objective was to assess the primary degradation products of InsP₆ in the rumen. Three diets differing in phosphorus and InsP₆ concentration (basal diet = 0.38% P in dry matter; high-P diet = 0.56% P; high-InsP₆ diet = 0.39% P) were fed to 3 ruminally fistulated lactating Jersey cows in a 3 × 3 Latin square. Ground concentrates (sieve size = 2 mm) were incubated in polyester bags in the rumen for 2, 4, 8, 16, and 24 h. The bag residues were analyzed for P, InsP₆, isomers of lower inositol phosphates (InsP₅, InsP₄, InsP₃), and crude protein. The InsP₆ disappeared more rapidly from cereal grains than from oilseed meals; however, after 24 h of incubation ≥95% InsP₆ had disappeared from all concentrates except hRSM (57%; diet average). Feeding the high-InsP₆ diet increased InsP₆ disappearance for oilseed meals, but not for corn and wheat. The predominant InsP₅ isomer in all bag residues was Ins(1,2,4,5,6)P₅ followed by Ins(1,2,3,4,5)P₅ and Ins(1,2,3,4,6)P₅. A further InsP₅ isomer [Ins(1,3,4,5,6)P₅] was detected in both rapeseed meal bag residues. Feeding the high-InsP₆ diet led to lower concentrations of Ins(1,2,4,5,6)P₅ and Ins(1,2,3,4,5)P₅, whereas an interaction between diet, concentrate, and time occurred for Ins(1,2,3,4,6)P₅ and Ins(1,3,4,5,6)P₅. The results confirm the high potential of rumen microorganisms to hydrolyze InsP₆; however, increasing the amount of InsP₆ in the diet can further enhance InsP₆ hydrolysis, which may be relevant when concentrates with slowly degradable InsP_6, such as RSM or heat-treated concentrates, are fed to dairy cows. Based on the concentrations of InsP₅ isomers, 3 and 6 phytases appear to play a major role in the rumen. Conversely, intrinsic plant phytase activity appears to be less relevant as the percentage of its primary hydrolysis product, Ins(1,2,3,4,5)P₅, changed only slightly upon using wheat known for high intrinsic phytase activity instead of the other concentrates. Additional information regarding the factors influencing the extent of ruminal InsP₆ disappearance will require further studies to determine the phytase activity of rumen microorganisms and the characteristics of their respective phytases.     

Effects of phytate and minerals on the bioavailability of oxalate from food

Phytate and mineral cations are both considered as important dietary factors for inhibiting the crystallisation of calcium oxalate kidney stones in susceptible individuals. In this paper, the phytate and mineral composition of whole bran cereals (wheat, barley and oat) and legumes were determined together with their soluble and insoluble oxalate concentrations in order to investigate the effects on oxalate solubility. The oat bran sample had the highest soluble oxalate concentration at 79 ± 1.3 mg/100 g, while total and soluble oxalate concentrations in the food samples studied range from 33 to 199 mg/100 g and 14 to 79 mg/100 g, respectively. The phytate concentration was in the range from 227 to 4393 mg/100 g and the concentrations of cations were in the range 54–70 mg/100 g for calcium, 75–398 mg/100 g for magnesium, 244–1529 mg/100 g for potassium and 4–11 mg/100 g for iron. Soluble oxalate concentration did not increase in proportion to total oxalate, and the phytate concentration in all foods was sufficient to contribute to an increase in soluble oxalate concentration by binding calcium.     

Nutritional quality of complementary food prepared from unmalted and malted maize fortified with cowpea using extrusion cooking

The nutritional quality of extruded unmalted or malted maize fortified with cowpea as complementary food was assessed based on its proximate analysis, amino acid composition and results from rat feeding with the blends. Results indicated a slight decrease and increase in protein content due to malting and extrusion respectively. The changes in fat, crude fibre and ash content were not significant. The blends were a good source of energy, ranging from 1831 to 2045 kJ per 100 g. Extrusion significantly increased the amino acid content of the blends, while malting had a varied effect on each of the amino acids. There was no significant difference in the protein efficiency ratio (PER), net protein ratio (NPR) and weight gain of rats fed the blends when compared with the control (casein diet). The present study shows that malting improved the nutritional quality of the blends. Rats fed the casein diet had higher values for total digestibility (TD) and net protein utilisation (NPU). There was no significant difference (P > 0.05) in the internal organ weights of rats fed all blends except the protein‐free diet. © 2000 Society of Chemical Industry     

Development of a bulgur‐like product using extrusion cooking

In this study we (1) developed a new bulgur‐like foodstuff using a durum wheat cultivar and an extrusion technique, (2) investigated the physicochemical properties of the extrudates produced and (3) sensorially evaluated the end‐product after cooking. Durum wheat was processed in a laboratory‐scale co‐rotating twin‐screw extruder with different levels of moisture content of the feed (367, 417 and 455 g kg^?1), screw speed (150 and 200 rpm) and feed rate (2.4 and 2.9 kg h^?1) to develop the bulgur‐like product. The effects of extrusion conditions on system variables (die pressure and specific mechanical energy (SME)), physical properties (die swell and bulk density), pasting properties (peak, trough and final viscosities) and cooking and sensory properties of the bulgur‐like products were determined. The results indicated that increased feed moisture content resulted in significant decreases in the die pressure and SME values of the extruded durum wheat products. As the moisture content and screw speed increased, the changes in die swell values were not significant. The lowest die swell and highest bulk density values were obtained at the highest feed moisture content. The extrusion variables also affected the pasting properties of the extrudates. Significant increases in each of the pasting properties occurred when the moisture content of the feed was increased. Some of the sensory properties (bulkiness, firmness, stickiness and taste–aroma) improved significantly as the feed moisture content increased, indicating better quality. Increased feed moisture content significantly improved cooking quality as determined by a decrease in colorimetric test results. Extrusion seems to be promising for the production of dry, relatively inexpensive bulgur‐like products with acceptable sensory properties. © 2003 Society of Chemical Industry     

The localization of phytate in tofu curd formation and effects of phytate on tofu texture

ABSTRACT:  The localization of phytate on tofu making and its effects on tofu texture were investigated. Thirty-eight percent and 3% of phytate in soymilk were bound to soluble protein and particulate protein, respectively, and the others were in free form. In the early stage of curd formation, phytate bound to particulate proteins and then a large part of phytate was taken into the tofu curd. Increase of phytate contents in soymilk resulted in the increase of coagulant requirement to make firm tofu. Optimal coagulant concentration (OCC) for making tofu was influenced by phytate contents. The increase of phytate in tofu caused decrease of hardness at OCC and resulted in the increase of brittleness and viscosity of tofu. We concluded that the phytate content is one important factor that contributes to tofu texture.     

Effect of oilseed protein concentrates and exogenous amino acids on the dialysability of iron and zinc

Iron deficiency anaemia and zinc deficiency have been persistent public health problems worldwide. Both deficiencies are attributed to poor bioavailability of minerals. The investigation was undertaken to study the effect of oilseed protein concentrates and exogenous amino acids on the dialysability of iron and zinc. Corn flour matrices with 10–20 g protein/100 g were formulated using groundnut and sesame protein concentrates. Dialysability of iron and zinc in natural and mineral fortified matrices was analysed. The effect of exogenous cysteine, histidine, glycine and lysine on mineral dialysability was analysed in groundnut and sesame protein concentrates. Dialysability of iron was enhanced with increasing protein concentration in matrices with groundnut protein but decreased in matrices with sesame protein. Dialysability of zinc increased with increasing protein concentration with both the protein concentrates. Among the amino acids, histidine enhanced dialysability of iron in natural groundnut and sesame protein concentrates, glycine in fortified groundnut and lysine in fortified sesame protein concentrates to a considerable extent. Dialysability of zinc was enhanced in natural groundnut, natural and fortified sesame protein concentrates by all amino acids. Amino acids definitely promotes the dialysability of iron and zinc, but its enhancing ability is highly specific to the food matrix.     

Rheological behaviour of wheat flour dough in twin-screw extrusion cooking

A capillary-type viscometer was designed to measure the apparent viscosity of the cooked wheat flour dough on -line in a twin-screw extruder. The effect of mean residence time and specific energy were studied in the ranges 20–45s and 300–800 kJ kkg⁻¹, respectively. A viscosity model was developed which accounts for effects of wall shear rate, moisture content and specific energy. It was shown that the extent of the cooking reaction is largely determined by the specific energy applied.     

Effects of cold extrusion process on thiamine and riboflavin contents of fortified corn extrudates

In this study, corn extrudates were produced from fortified corn flour by conventional and cold extrusion techniques at different barrel temperatures of 80, 110, 130 and 80 °C, respectively, and feed moisture contents. Thiamine and riboflavin contents of extrudates were determined by HPLC. Thiamine contents of the samples produced at feed moisture contents 20% and 25% decreased as temperature increased. There was no significant difference between riboflavin contents of conventional extrudates produced at both feed moistures at 80 and 110 °C barrel temperatures. However, riboflavin content of extrudates produced at 20% feed moisture was higher than the one produced at 25% feed moisture at 130 °C. In cold extrusion, there was no significant difference between riboflavin contents of samples. The samples produced by CO₂ injection had the lowest expansion index and uniform air cells. However, the samples produced by conventional extrusion had higher expansion index and size distributions of air cells were not uniform.     

改良挤压法制备铁营养强化大米的研究

以早籼米碎米为原料,使用乙二胺四乙酸铁钠（NaFeEDTA）做铁营养强化剂,通过改良挤压法制备铁营养强化大米。采用响应面法考察改良挤压法加工参数,（物料含水率、螺杆转速、机筒温度）的变化对铁营养强化大米质构特性的影响,并且以市售晚籼米质构特性为参考指标,优化铁营养强化大米的制备工艺。得到接近晚籼米质构的最佳工艺条件为湿基物料含水率34％,螺杆转速25r／min,机筒四区温度为102℃,其余四个加热区的温度分别为50、65、90、95℃。此条件下制备的营养强化大米硬度为6062g,粘附力为-1175．21g·s,弹性为0．72,内聚性为0．61,接近市售晚籼米的质构;铁含量为36．95mg／kg,远高于晚籼米的7．21mg／kg,并且淘洗蒸煮损失较小,为其他营养强化米的生产提供理论参考。     

Effect of high moisture extrusion cooking on protein–protein interactions of pea (Pisum sativum L.) protein isolates

This study focuses on protein alterations in fibrous meat substitutes produced by high moisture extrusion cooking of pea protein isolates. Three commercially available pea protein isolates and their respective extrudates were evaluated regarding their amino acid composition, molecular weight distribution and protein–protein interactions. Extrusion had no effect on the degree of hydrolysis and amino acid composition indicating that the thermal and mechanical energy during extrusion did not cause the formation of peptide bonds or the degradation of amino acids due to Maillard reactions. Decrease of protein solubilised from extrudates in a buffered solution containing urea indicated that the structural integrity of extrudates could be attributed mainly to covalent disulphide bonding and, to a smaller extent, to non‐covalent interactions. Additionally, the disappearance of legumin bands in extrudates as determined by electrophoresis could be explained by its participation in a macromolecular network that was aggregated and cross‐linked via disulphide bonds. This study contributes to a better understanding of the way the proteins interact during extrusion of pea protein isolates.