MECHANICAL AND WATER-HOLDING PROPERTIES OF HEAT-INDUCED SOY PROTEIN GELS AS RELATED TO THEIR STRUCTURAL ASPECTS

The dependence of mechanical and water-holding properties of soy protein gels upon their structures was examined. Gels varying in extent of network formation were prepared by heating 20% paste of the isolated soy protein (ISP) containing L-cysteine hydrochloride (CySH) which has an ability to cleave intermolecular disulfide bonds. A rapid decrease in gel hardness and cohesiveness was observed with the increase in added amount of CySH up to 2.5 times 10^-5 mole/g ISP, and then a gradual decrease to 5.0 times 10^-5 mole/g ISP. The changes in these mechanical parameters appeared to depend on the degree of the network formation interpreted from the solubility changes of gels in the phosphate buffer containing 6 M urea. The relaxation time, estimated by compression stress relaxation, was also dependent on the degree of the network formation, while the modulus of elasticity was hardly affected. On the other hand, there was an inverse correlation between the NMR line width of the water proton and expressible water by the pressure method as an index of water-holding properties of the gel; the broader the former, the lesser the latter. The change in the water-holding capacity estimated from expressible water was also associated with that in the degree of the network formation. This confirms that both mechanical and water-holding properties of the gel are qualitatively governed by the extent of the structure formation controlled by the intermolecular disulfide bonds.     

MECHANICAL PROPERTIES OF SATSUMA ORANGE AS RELATED TO THE DESIGN OF A CONTAINER FOR BULK TRANSPORTATION1

The mechanical properties of Satsuma oranges were studied under static, quasi-static and impact loading in order to determine conditions leading to minimum fruit injury in containerized shipping. The results indicated that the use of containers is safe for a 70h transport provided the stacking height does not exceed 70 cm. The static load at the bottom of the container should not exceed 2 kg per fruit if permanent deformation is to be avoided; the fruit ruptures when the load exceeds 4.2 kg per fruit. The time-deformation curve under static load was explained with a Burgers model modified with a sliding element. Bruising energy by impact was 3 times and that by quasi-static loading 1.4 times as great as that by static loading. The relationship between impact acceleration and dropping height of single fruits agreed well with the Hertz’ theory of colliding spheres for dropping heights up to 15 cm.     

MECHANICAL CHARACTERIZATION OF FIBROUS MATERIALS AS RELATED TO MEAT ANALOGS **

Abstract. Using a composite material approach, fiber concentration and orientation were analyzed for their effect on mechanical properties of synthetic meat systems. Egg albumen binder soy fiber and Silastic rubber cotton thread systems were tested experimentally. Dynamic compressive and parallel creep shear tests were conducted to determine time dependent elastic and shear moduli. The maximum compressive modulus occurred with the fiber parallel to the loading direction while the shear modulus was greatest with the fibers at a 45d? orientation. The compressive modulus was minimum at a fiber orientation perpendicular to the load. Experimental values for the shear modulus were minimized at 0d? and 90d? orientation. Higher fiber concentration resulted in higher compressive and shear moduli for both experimental two-phase systems.     

TEXTURE AND STRUCTURE OF CRISPY-PUFFED FOOD PRODUCTS PART II: MECHANICAL PROPERTIES IN PUNCTURE

A puncture test was used to describe the mechanical and textural behavior of crispy-puffed food extrudates. Four criteria were identified from the force-time curves: (1) the average puncturing force, F_m, (2) the spatial frequency of structural ruptures, N_wr, (3) the average specific force of structural ruptures, f_wr, and (4) the crispness work, W_c. The discriminating power of these criteria was shown through the effects of moisture content and recipe composition in the extrusion-cooking process. Relationships between puncture criteria were also studied. The effect of water activity showed that the force related criteria described well the mechanical behavior of expanded extrudates.     

TIMING OF CALCIUM TREATMENT ON RESISTANCE OF RAW AND CANNED DICED TOMATOES TO MECHANICAL ABUSE

Tomato dices are typically treated with calcium (Ca) to increase firmness and resistance to mechanical abuse. However, studies have not examined when the application of Ca would provide the greatest protection and result in the greatest firmness. Tomato (cv. P696) dices were dipped in a 600 mg/L calcium chloride (CaCl ₂ ) solution either before or after undergoing mechanical abuse for 0–240 s in a rotary drum. The drained weight and firmness, which were measured using a Kramer shear cell (Instron Corp., Canton, MA), did not depend on whether Ca was added before or after the mechanical abuse. However, sensory evaluation showed that the panelists preferred the diced tomatoes that were dipped in Ca before undergoing mechanical abuse. These tomato dices appeared to have a larger percentage of undamaged dices, while those that were mechanically abused before dipping in Ca appeared ragged and mushy because of a collapsed structure. Therefore, although there was no significant difference in the drained weight or texture obtained by instrumental measurement, dices that are dipped in Ca before undergoing mechanical abuse appear less damaged to consumers.     

THERMAL BEHAVIOR OF PORCINE COLLAGEN AS RELATED TO POST-MORTEM TIME

SUMMARY: DTA (differential thermal analysis) thermograms of epimysial connective tissue from normal and low quality porcine muscle were compared at 0 and 24 hr post-mortem. In addition, the melting characteristics of intramuscular collagen were determined at 0 hr post-mortem. In all tissues studied, collagen from low quality muscle consistently gave slightly lower peak melting points than that from normal muscle. Epimysial collagen had a significantly ( P < .05) lower peak melting point at 24 hr than at 0 hr post-mortem (64.24 vs. 65.77°C). Using epimysial collagen, a significantly ( P <.01) greater proportion of the total melting range occurred at lower temperatures at 24 hr post-mortem as compared to 0 hr (4 1.1 vs. 30.9%). The thermal behavior of intramuscular collagen at 0 hr post-mortem was similar to that of epimysial collagen at 0 hr, but peak melting temperatures were slightly higher for intramuscular connective tissue.     

POTATO FLAVOR AS RELATED TO CHEMICAL COMPOSITION

SUMMARY— A study was made on the relationship of flavor of potatoes to their phenolic and ascorbic acid content. Material for the study was from two main sources: (1) clones that are hybrids between varieties of Solanum tuberosum subsp. tuberosum grown in New York and varieties of Solanum tuberosum subsp. andigenum grown in Peru; (2) established commercial American varieties such as Ontario, Pontiac, and Katahdin. Bitterness and astringency were selected as the character notes most related to phenolic content. A significant correlation was found between phenolic content and bitterness and a highly significant correlation between phenolic content and astringency. No significant correlation was found between ascorbic acid content and flavor.     

WEIGHTS OF BROILER PARTS AS RELATED TO CARCASS WEIGHTS AND TYPE OF CUT

960 broiler carcasses weighing from less than 450 to 2000g were individually tagged and cut using eight commercial cutting techniques. Percentages of the different pieces to whole carcass weight ranged from 17.2% for split breast with back to 5.4% for drumstick portions. Percentages of the smaller breast pieces, particularly the quartered breast, the keel and the wishbone, approached those of the wing, thigh and drumstick, thus facilitating portion control. The validity of using one mean percentage for each piece over all carcass weights was established by statistical analysis of all data relating piece weight to carcass weight, For all pieces the predictability of weights was greatest when the piece was obtained by cutting through well defined anatomical features such as a joint.     

DIELECTRIC PROPERTIES OF SHRIMP RELATED TO MICROWAVE FREQUENCIES: FROM FROZEN TO COOKED STAGES

Dielectric properties of shrimp (Penaeus sp.) were measured at frequencies between 0.3 and 3 GHz from -25 to 70C by using a network analyzer. The relationship between dielectric properties and temperature was determined at 915 MHz and 2450 MHz. Below the freezing point, the dielectric constant (?′) and dielectric loss factor (?″) increased rapidly with increasing temperature as ratio of frozen water in shrimp was decreasing. Above the freezing point, the dielectric constant (?′) decreased as frequency and temperature increased at both frequencies. The dielectric loss factor (?″) did not change significantly with temperature. The relationships between penetration depth and temperature at both frequencies were evaluated from the experimental data.     

BOVINE MUSCLE TENDERNESS AS RELATED TO PROTEIN SOLUBILITY

ABSTRACT— The longissimus (modest degree of marbling) from forty beef ribs selected 48–56 hr post-mortem was used in two trials. Trial I involved A, C and E maturity ribs (10 each classification). Each rib was subjectively scored for texture (fresh) and adjacent longissimus samples were removed for the determination of protein solubility (fresh) and tenderness. Tenderness (cooked muscle) was measured with a Warner-Bratzler shear and taste panel. Protein solubilities were determined using 0.154M Krebs-Ringer-Bicarbonate buffer, 0.2M KCl + 0.01M K phosphate buffer, 1.1M Kl + 0.1M K phosphate buffer, and 0.03M K phosphate buffer. Trial II involved 10 A maturity ribs. The 0.2M KCl, 1.1M Kl and 0.03M K phosphate buffers as described for trial I were used for protein extraction. Additionally, sarcomere length was measured in formalin. Multiple regression equations were developed to predict tenderness in trial II. Protein solubilities were not significantly different between the carcass maturity groups although there were trends toward increased solubility as maturity increased. Tenderness tended to decrease from A to E maturity indicating a negative relationship between protein solubility and tenderness. Several significant negative correlations between protein solubility and tenderness were found in trial I (A maturity group) and trial II. Additionally, several significant negative correlations between texture and solubility were calculated. Correlations within the C and E maturity groups were variable and showed no definite trends. Multiple regression analyses showed that a combination of protein solubilities, texture score and sarcomere length accounted for 88% of the variation in shear force and 72% of the variation in taste panel tenderness.     

INTRAMUSCULAR LIPIDS IN M. LONGISSIMUS DORSI FROM PORK, AS RELATED TO BREED AND SENSORY PROPERTIES

The content, composition and distribution of intramuscular lipids in M. longissimus dorsi (LD) of pure bred Hampshire, Swedish Landrace and Swedish Yorkshire pigs were investigated. The highest content of intramuscular lipids was found in Hampshire (2.0%). Swedish Yorkshire had on an average 1.8% intramuscular lipids and Swedish Landrace 1.4%. About 35% of the fatty acids are saturated, 51–56% are monounsaturated and 8–12% are polyunsaturated. The content, as well as the fatty acid composition of the intramuscular lipids, were influenced by breed and sex and most probably also by genetic factors. The intramuscular lipids were mainly found in fat depots containing 20 to 150 fat cells. The fat depots were situated in the perimysium and, to some extent, in the endomysium. The fat cells had mostly an elliptical shape. The diameter of the fat cells varied between 15 and 180 μm but a diameter of 30–60 μm was most frequently noted. An increase in fat depot size was related to an increase in fat cell diameter. For the Swedish Landrace breed a relationship between the sensory properties of LD and the content and the distribution of intramuscular lipids was noted. The sensory properties of Yorkshire were related to the content, composition and distribution of intramuscular lipids, whereas no relationship was noted for the Hampshire breed.     

PTT纤维的基本力学性能研究

主要介绍了PTT纤维的截面形态,对PTT纤维的力学性能和在不同夹持方式下力学性能的变化进行了研究,与PET纤维进行力学性能比较,经过实验分析得到,湿态下PTT纤维和干态PTT纤维的初始模量、断裂强度几乎无变化,而湿态的PTT纤维伸长率比干态时高。干态时PTT纤维的初始模量、断裂强度均低于干态PET纤维;PTT纤维在结节状态下断裂强度和断裂伸长率小于在勾结状态下的断裂强度和断裂伸长率。