Gel Characteristics—Waterbinding Properties of Blood Plasma Gels and Methodological Aspects on the Waterbinding of Gel Systems

A methodological study on the waterbinding properties of protein gels was made, where two tests were evaluated. Only one of them, the “net test,” was found useful for work on protein gels. The moisture loss of blood plasma gels was then studied as a function of heating temperature, heating time, pH, protein concentration, and sodium chloride concentration. It was finally demonstrated that a change in the gel structure may affect waterbinding and texture characteristics differently, and these properties should therefore be treated separately when evaluating protein gels. It was, e.g., shown that blood plasma gels became firmer with increasing heating temperature from 72 – 92°C, whereas the waterbinding properties became poorer at temperatures above 77°C and had an optimum at 75 – 77°C.     

Gel Characteristics—Compression and Penetration of Blood Plasma Gels

Compression and penetration studies of blood plasma gels showed that registered forces above a certain degree of deformation increased with the heating temperature during gelation, pH in the range of 6-9, the protein concentration in the range of 4 - 6%, and by the addition of 1 - 5% sodium chloride. Generally, the information obtained from compression and penetration tests were in agreement. The initial slopes proportional to the “rigidity modulus” changed differently with the variables studied. The initial slope did not change when pH was changed from 6 to 10 in spite of the structural changes involved, whereas the initial slope increased with increasing heating temperature and protein concentration.     

Functional Properties of Heat Induced Gels from Liquid and Spray-Dried Porcine Blood Plasma as Influenced by pH

The properties of gels obtained from porcine blood plasma were studied under different pH conditions. Gels from liquid and spray-dried plasma were prepared and analyzed for water holding capacity (WHC), texture, and microstructure at pH 7.4, 6, 5.5 and 4.5. The denaturation extent of proteins was also determined by differential scanning calorimetry (DSC). All properties studied were dependent on pH. The WHC and consistency of gels decreased when pH decreased. These results correlated with microstructural changes observed by SEM. Spray drying affected the consistency of gels. The penetration force of the gel from dehydrated plasma was always lower than that prepared from liquid plasma where the pH was the same, but neither the WHC nor the micro-structure of gels were affected.     

Capillary Pressure as Related to Water Holding in Polyacrylamide and Chicken Protein Gels

The ability of food gels to hold water affects product yield and organoleptic quality. Most researchers believe that water is held by capillarity such that gels having smaller mean pore diameter and a more hydrophilic surface hold water more tightly. To date, however, only qualitative evidence relating pore size to water holding (WH) properties has been provided. The present study sought to provide quantitative confirmation of this hypothesis. Scanning electron microscopy coupled with image analysis was used to measure pore size, and water contact angle with the gel surface was measured by the captive bubble method, in both model polyacrylamide gels and heat‐induced protein (minced chicken breast) gels. These were related to water lost during cooking of meat pastes to form gels (cooking loss (CL)), as well as water lost upon centrifugation (expressible water (EW)) or by capillary suction (CSL) of all prepared gels, as inverse measures of WH. As predicted by the Young–Laplace equation for calculating capillary pressure, the presumed mechanism of WH, gels with lower water losses exhibited a more hydrophilic surface (smaller contact angle). Yet, both lower CL and CSL correlated with larger mean pore diameter of gels, not smaller as had been expected. Polyacrylamide gels varied more in WH than did prepared meat gels, yet only the capillary suction method was sensitive enough to detect these differences. Practical Application: The ability of gels to hold water is important for economics of processing, food quality, and food safety. This study investigated the prevailing theory for how gels hold water, capillarity. Both the pore sizes of gel microstructures and the degree of hydrophilicity of the polymers comprising each gel were quantitatively assessed and related to water holding (WH) properties, and this was the first report using such methodologies. It appeared that the degree of hydrophilicity was much more important explaining WH properties than pore size, and that future research of this kind should be carried out.     

Strength of Protein Gels Prepared with Microbial Transglutaminase as Related to Reaction Conditions

Influence of gelling reaction conditions on the strength of several protein gels prepared with microbial transglutaminase (TGase) was investigated. A method was developed to gel proteins and measure gel breaking strength in a micro well plate. Enzyme concentration range for maximum gel breaking strength varied from 10 to 40 units/g protein. Maxima gel breaking strengths were achieved at 50°C for SPI, caseinate and gelatin and 65°C for egg yolk and egg white proteins. Optimum pH resulting in strong gels was pH 9 for SPI, caseinate, and egg yolk, and pH 6 for gelatin and egg white. Adjusting pH was promoted in egg white the formation of ?-(γ-glutamyl)lysine crosslinks and increased its gel breaking strength.     

工艺条件对猪血凝胶质构特性和持水力的影响

研究纯血含量、加热温度、加热时间及NaCl添加量等工艺条件对猪血凝胶质构性质、持水性和感官品质的影响。单因素试验表明,工艺条件对硬度、咀嚼性、回复性、持水力及感官品质影响显著。猪血蛋白含量越高,硬度、咀嚼性及持水性越大,但蛋白含量过高时,回复性降低;温度升高和加热时间延长均使得硬度和咀嚼性提升,但过高的温度和过长的加热时间对保持凝胶的回复性和持水力不利;低添加量的NaCl可提高凝胶品质,但高添加量的NaCl使持水力、硬度、咀嚼性及回复性降低。适宜的加工条件为猪血蛋白添加量为15.49~17.42g/100mL,温度90~95℃,时间10~20min,NaCl添加量3~4g/100mL。进一步的相关性分析结果显示,持水力对猪血凝胶的感官品质具有决定作用,硬度、咀嚼性和回复性与凝胶持水力之间的相关性显著,且能够较好地反应猪血凝胶的质构特性。     

Texture and Microstructure of Heat-Formed Egg White Gels

Egg white gels were formed by heating liquid egg white at various pH, protein, and NaCl levels at different temperatures and times of heating. Hardness, cohesiveness, and springiness of gels were measured. Serum was expressed from gels and evaluated by polyacrylamide gel electrophoresis. Selected samples were prepared for scanning electron microscopy. Gel hardness rose with increasing temperature, time, pH, and protein level, and decreased with added salt. Cohesiveness and springiness increased with time and temperature of heating. Expressed serum decreased as pH, time, temperature, and protein level were increased. Gels at pH 5 and 6 had a coarse, aggregated structure. At pH 9 protein strands and globules were arranged in a uniform matrix. Salt prompted aggregation of gels.     

酸奶凝胶的结构特性及其影响因素

本文主要说明了酸奶凝胶的结构,物理特性及其影响因素。酸奶凝胶超微结构呈一种纤维网状立体结构,网状纤维中间形成无数有规则的空隙。均质,热处理等加工因素对其质地有不同的影响。     

影响猪血浆蛋白热诱导凝胶质构特性及持水性因素的研究

本实验研究在一定的加热条件下猪血浆蛋白质量浓度、加热温度、加热时间、离子种类、离子强度和pH 值对猪血浆蛋白热诱导凝胶的质构、持水性等性质的影响。利用质构仪测定猪血浆蛋白热诱导凝胶的硬度和黏附性,利用离心的方法测定凝胶的持水性。结果表明,在80℃下加热45min,猪血浆蛋白质量浓度超过6g/100mL可以形成凝胶,并且随蛋白质量浓度的增大,凝胶强度和持水性也增大;凝胶强度随pH 值(3～9)增加而增大,pH5 时凝胶的持水性最小,pH3 时最大;NaCl 浓度0.2mol/L,CaCl2 浓度0.6mol/L 时,凝胶硬度最大。实验得出,猪血浆蛋白热诱导凝胶的质构特性及持水性受许多因素影响,在实际生产中应该控制加热条件,以获得高质量的凝胶。     

Frozen Hake Fillets Quality as Related to Texture and Viscosity By Mechanical Methods

This work aimed to develop a textural quality classification function for frozen hake fillets using instrumental measurements. Frozen hake fillets were stored to provide a wide range of textures. Raw and cooked fillets were analyzed for texture using Kramer and Warner-Bratzler shear cells and a puncture device. Apparent viscosity, dimethylamine and protein solubility were also measured. Principal Component Analysis indicated three factors accounted for 86.5% of the variance. Four clusters were found, ranging from excellent quality (low texture, high viscosity) to very poor (high texture, low viscosity). Parameters required for classification were viscosity, maximum force from Kramer and maximum force and energy from the puncture test.     

Amylose and Protein Contents of Rice Cultivars as Related to Texture of Rice-based Fries

Mixtures of short-, medium-, and long-grain rice flours, defatted rice bran, salt, and water were extruded and fried to produce French fry-like products. Amylose and protein correlated positively with instrumental measures of hardness and gumminess. Water contents of frozen and fried fries correlated negatively with hardness and gumminess. Low protein rice cultivars retained more water than high protein cultivars during extrusion followed by cooling. Amylose content correlated negatively with water content of fried fries. Fries formulated from waxy rice had hardness and gumminess comparable to commercial French-fried potatoes, but all other fries were too hard and gummy.     

Histological Development of the Green Bean Pod as Related to Culinary Texture.

SUMMARY— The basic pattern of tisue origins is well established in the bean pod when the unopened flower bud is less than 3.0 mm long. An outer epidermis (protoderm) with many hair-like outgrowths forms the outermost tissue of the young pod. A subjacent layer one cell deep forms a hypodermis. Inwardly, a zone 8 to 10 cells deep of enlarging and vacuolating cells forms the young outer parenchyma of the growing pod. Within the innermost half of this zone, the meristematic stage of vascular tissues (procambium) is differentiated.
An inner epidermis (protoderm) and an ill-defined hypo-dermis line the pod cavity. The young inner epidermis is continuous with the outer epidermis of the young seed (ovule). Cell divisions in the inner epidermis and its hypo-dermal layer initiate an inner parenchyma and fiber sheath, respectively, approximately at the end of flowering. The inner parenchyma becomes extensive in early post-floral stages. At the same time, the initials of the fiber sheath become sharply differentiated by cell elongation at a 45° angle to pod length, and assume the characteristics of young fiber cells (sclereids).
Cell divisions cease first in the outer parenchyma, and most post-floral growth of this tissue is by cell enlargement. Cell divisions persist through early post-floral growth in the inner parenchyma, young fiber sheath, procambial tissues and outer epidermis. These differences in origin and rates of early development of pod tissues foreshadow marked differentiation and structural specializations that are significant to textural qualities at culinary maturities.     

Structural Changes Related to Texture of Pre-Peeled Potatoes

Pre-peeled potatoes, treated with heated ascorbic/citric acid solutions to control browning, undergo firming and separation of superficial tissues that affect texture after mashing and slicing following cooking. Examination of superficial parenchyma cells in cooked potatoes by scanning and transmission electron microscopy indicated greater cell wall rigidity and middle lamella retention in samples treated with browning inhibitors than in untreated controls. Lumps in mashed potatoes prepared from treated samples showed similar characteristics. Treated samples sometimes displayed a discontinuity beneath the superficial tissue, corresponding to site of tissue separation during slicing. These observations are consistent with treatment-induced changes in cell wall and/or middle lamella pectins as the cause of such textural defects.     

加热方式对血浆流变学及质构性质的影响

血浆作为血液的主要成分之一,经加热可以形成凝胶,而凝胶的质构和流变性质直接影响着血浆产品的品质.研究3种不同的加热升温方式(1℃/min、3 ℃/min以及90℃恒温)对鸭血浆和猪血浆的质构及流变学性质的影响,结果表明血浆种类和升温方式都会影响血浆凝胶的质构和流变学性质.鸭血浆形成凝胶的硬度及最终G’值均高于猪血浆,1℃/min升温方式形成的猪血浆凝胶硬度最高,90℃恒温加热升温形成的凝胶硬度最低,并且血浆在1℃/min升温方式下形成的凝胶质构特性与在3℃/min以及90℃恒温升温方式下形成的凝胶质构特性有着显著差异,后两者形成的凝胶质构特性基本类似.不同血浆种类采用相应加热方式,可以达到调控血浆热致凝胶的硬度的目的.     

Linear Programming and Response Surface Methodology to Optimize Surimi Gel Texture

A formulation optimization study was conducted on surimi gels prepared with starch, and/or raw egg white employing the stepwise method (SM), linear programming (LP), and response surface methodology (RSM). At 78% moisture, the greatest gel strengthening and reduction of expressible moisture occurred at 8% starch, 6% egg white, or a combination of 5% starch and 5% egg white for SM, 5.33% starch and 4.33% egg white for LP, and 3.5% starch and 5% egg white for RSM. RSM resulted in gels with the greatest strength (compressive and penetration forces), followed by LP and SM. The RSM enabled more accurate prediction of textural behavior of final product at various ingredient combinations than the SM or LP.     

小麦淀粉凝胶质构特性研究

为了掌握不同小麦品种淀粉凝胶质构特性;陕西关中小麦品种和西澳面条用小麦品种的淀粉凝胶质构的异同;淀粉的直链淀粉含量、色度及粘度特性与淀粉凝胶质构特性的关系。以参加陕西省关中小麦品种区域试验的15个小麦品种(品系)、西澳8个面条用小麦品种(品系)为材料,研究了小麦品种淀粉凝胶质构特性及淀粉特性与凝胶质构特性的关系。结果表明:不同小麦品种淀粉凝胶质构特性不同,陕西关中小麦品种之间淀粉凝胶质构特性比西澳面条小麦品种之间差异大。直链淀粉含量与凝胶特性无明显关系;色度中L值与凝胶硬度呈显著正相关;粘度特性与淀粉凝胶质构特性显著相关。关中小麦品种小偃6号、小偃128、秦农068和西澳面条小麦品种具有相似的凝胶质构特性。     

Penetration Studies of Blood Globin Gels

Studies were made on the effect of temperature, pH and protein and salt concentration on the penetration force withstood by globin gels. The registered force increased with heating temperature (60 - 95°C) and protein concentration (1.4 - 5.0%). The gelation pH was dependent on both protein and salt concentration; the higher the protein or salt concentration the lower the gelation pH. At 3% protein concentration globin formed a gel around pH 5 - 6. At 0.7% concentration and higher, the presence of salt weakened the gel strength, while the addition of plasma increased the gelation pH of salt-containing globin gels. A substantially higher penetration force was measured for bovine globin gels than porcine globin gels. Further concentration and spray-drying decreased the gel strength of globin gels.     

Morphology and Texture of Bologna Sausage as Related to Content of Fat, Starch and Egg White

The effects of fat (7.0, 14.0 and 20.0%), starch (0, 5 and 10%) and egg white (0, 1.5 and 3%) on the microstructure and texture of bologna sausages were examined. As levels of fat and starch increased, the microstructure exhibited increasing numbers of holes (P<0.05), smaller in size (P<0.05) and similar (P>0.05) in shape. No clear relationship was found between addition of egg white and these morphological variations. Low-fat sausage (7.0%) was less hard and chewy (P<0.05) than high-fat (20.0%) sausage; likewise, a direct relationship was found between starch and egg white content and hardness and chewiness of the bologna.