Influence of Sodium, Potassium and Magnesium Chloride on Thermal Properties of Beef Muscle

Sodium, potassium and magnesium chloride, at 1.25, 2.50 and 5.00%, were studied using differential scanning calorimetry. Increasing NaCl resulted in decrease in myosin transition temperature (T₁, first transition) and enthalpy (H₁); both showed significant (P<0.05) linear response. The sarcoplasmic proteins and collagen denaturation temperature (T₂, second transition) increased significantly over the control when 1.25% NaCl was added, but were the same as control when 2.5% and 5.0% were used. Actin denaturation temperature (T₃, third transition) tended to increase when NaCl was added, but enthalpy decreased. Potassium chloride showed similar effects to NaCl on T₁, T₂, H₁ and H₃. Increasing magnesium chloride had much more pronounced effect on decreasing second enthalpy compared to the monovalent salts. At 5% MgCl₂ T₁ increased significantly.     

EFFECT OF LIGHT SOURCE ON ACCEPTABILITY OF CITRUS FRUITS

The effect of three commonly used light sources on the color acceptability of oranges, lemons and limes was investigated. The color of the oranges under incandescent (INC) and metal halide (MH) lights was more preferred (P<0.05), by the panelists than when presented under fluorescent (FL). The main reason was the dull orange color seen under FL light. Relative luminance data, collected via a fiber optic probe connected to a photo diode array, demonstrated the reason to be insufficient red light reflected from oranges presented under FL. The yellow lemons were also preferred more under INC and MH than under FL: the latter resulted in a greenish tinge appearance. The color of the limes was more preferred under INC light than under FL, but preferred equally to the product presented under MH.     

STRESS RELAXATION TEST CONDITIONS FOR MEAT PRODUCTS TO MEASURE VISCOELASTICITY

The effects of various test parameters on stress relaxation analysis measuring viscoelastic properties of beef products, and the suitability of different models to describe that test data were investigated. Three types of processed meat products were evaluated: finely comminuted (frankfurter), ground beef (salami), and whole muscle (corned beef). Cylindrical specimens of meat products, 10, 15 or 20 mm in diameter and 10 mm in length were compressed to 10%, 20% or 30% of their original height for 9 min. The data were fitted using the Maxwell model with two elements and other available models in the literature. Stress was calculated by dividing the force by initial cross sectional area of the sample, and modulus by dividing stress by strain. Both sample size and compression ratio affected model parameters. A diameter to length ratio (D/L) of 1.5 and any compression ration were suitable for the whole muscle product; D/L of 1.5 and 10% or lower compression for ground beef; and D/L of 2 and 10% or lower compression ratio for finely comminuted products were the suitable test conditions.     

CHEMICAL MODIFICATION EFFECTS ON TEXTURE AND GELATION PROPERTIES OF FINELY COMMINUTED BEEF

The effects of various chemical modifications on gelation and texture of finely comminuted lean beef mixes were investigated. Urea, which disrupts non-covalent bonds, significantly increased (at 95% level) the modulus of rigidity (G) and hardness values compared to the control (no additive). Oxidation of free sulphdryl groups by H₂O₂ resulted in lower G but similar hardness values of the control. The β-mercaptoethanol (ME) treatment was similar to the control in G values but higher in hardness, gumminess and chewiness. Ethylenediamine tetraacetic acid (EDTA) addition resulted in excessive cooking losses, the lowest G value and the hardest texture. Polyoxyethylene sorbitan monooleate did not have any significant effect on the textural characteristics of the finely comminuted mixes but resulted in lower G compared to the control.     

OPTIMUM CONDITIONS FOR DETERMINING WATER HOLDING CAPACITY OF BEEF BY THE PRESS METHOD

Water holding capacity (WHC) of ground beef was measured by the press method. Three levels of applied force, test duration, sample mass, and salt concentration were investigated. Three types of deformations – plastic, elastic and permanent were used to explain the effects of applied force on WHC. Viscoelastic properties explained the effects of test duration. In general, WHC decreased with additional applied force and test duration, and increased with a larger sample size and salt concentration. Recommended test conditions are: 1 g sample size, 20 kN force for 2 min at a salt concentration of 0, 1 or 2%.     

Cold Stage Scanning Electron Microscopy Study of Meat Batters

Cryo scanning electron microscopy (Cryo SEM) was used to study the microstructure of raw and cooked meat batters and compared with conventional SEM and transmission electron microscopy (TEM). Cryo SEM revealed that raw batters consisted of an organized, highly interconnected protein matrix in which fat globules were dispersed. Cryo SEM resulted in much better preservation of protein gel structure compared to conventional SEM which caused shrinkage of the specimen, resulting in a closed gel matrix structure. TEM confirmed the differences between the matrices of raw and cooked batters shown by cryo SEM. Methods for preparation of specimen for cryo SEM were developed.     

Rheological and Gelation Properties of Meat Batters Prepared with Three Chloride Salts

The gelation and rheological properties of poultry meat emulsions prepared with three chloride salts (NaCl, KCl, MgCl₂) and 50/50 mixtures of the above salts at isoionic strength (IS = 0.42) were studied. The relationship between shear rate and shear stress for the different raw meat emulsions was found to be nonlinear and followed Bingham pseudoplastic behavior. The yield stress for the emulsion containing only MgCl₂ was significantly lower as compared to all the other treatments. The highest rigidity modulus values obtained during cooking were observed in the NaCl + MgCl₂ treatment followed by the NaCl + KCl, NaCl and KCl. The emulsion containing MgCl₂ only broke down at the initial stages of cooking, exhibiting the destabilizing effect of the magnesium cation.     

一种代替氢氧化钙的无灰膨胀剂

将用常规工艺浸水、酶脱毛的小牛皮,分别用不同用量的氢氧化钙、氢氧化钠、NA-N膨胀剂进行碱膨胀,测定碱膨胀不同时间碱皮和蓝皮Ts、膨胀液中羟脯氨酸的含量、脱碱后裸皮进行组织切片后的显微镜观察图、成革的物理力学性能.结果表明:NA-N膨胀剂处理后的效果比用氢氧化钙处理后的效果还要好,因此NA-N膨胀剂一种可以代替氢氧化钙作为小牛皮革的清洁生产材料.     

Sn基Ⅷ型笼合物Ba_8Ga_(16)Sn_(30)热电材料研究进展

Ⅷ型Sn基笼合物Ba8Ga16Sn30由于具有优异的热电传输特性而被认为是最具有应用前景的热电材料之一。介绍了Ⅷ型Sn基笼合物的晶体结构、合成方法及理论和实验方面的研究情况,并对有关研究进展进行评述,同时提出进一步研究该笼合物的一些建议。