Low Temperature Blanching Effects on Chemistry, Firmness and Structure of Canned Green Beans and Carrots

Green beans and carrots were canned using extended blanching at 64–65°C and added calcium and/or acid. Firmer products resulted from all treatments but lowered pH was most effective. Blanched green beans were firmer with lower pectin esterification, indicating pectin methyl esterase activity. Green beans and carrots treated with calcium and/or acid and then cooked were firmer than controls. Acid exhibited a firming effect, perhaps by loosening tissue, while calcium reduced the influence of heat. Instrumental bioyield values correlated with sensory results of canned green beans; bioyield may result from a scleriformic layer. Microscopy showed firmer beans had intact middle lamellae while softer samples contained separated cells. These data suggest that the treatments rendered pectates in the middle lamella less heat labile.     

Changes in the Melting Characteristics of Bovine Tendon Collagen Induced by a Bacterial Collagenase

Differential scanning calorimetry was used to study the changes produced by a commercial Clostridium histolyticum collagenase preparation on the melting behavior of bovine Achilles tendon collagen. The samples were heated at 5°C/min from 25 to 100°C. As a result of proteolysis, the collagenase-treated samples were partially gelatinized at 25°C and, during the calorimetric experiments, exhibited significant decreases in their melting transition parameters when compared to intact collagen. The denaturation temperatures and enthalpies obtained were 61.6°C and 44.4 J/g sample for intact collagen and 43.6°C and 26.1 J/g sample for collagenase-treated collagen. These differences may be accounted for by changes produced in the structural organization of the collagen fibrils by the collagenase treatment.     

Water-Holding Capacity in Hard-to-Cook Beans (Phaseolus vulgaris): Effect of pH and Ionic Strength

The effect of pH and ionic strength (IS) of soaking solution on the water holding capacity (WHC) of hard-to-cook (HTC) and control black beans (Phaseolus vulgaris) was evaluated. Beans were soaked 18 hr in solutions covering the pH range 1–7 at constant IS (1.0 M) or in solutions ranging in IS from 0.01 to 1.3M (prepared with either NaCl or CaCl₂) at pH 7. WHC was significantly reduced in the pH range 3.5 to 5.1 in control beans but the effect was not as pronounced with HTC samples which had a lower WHC at each pH. Solutions prepared with NaCl produced significantly lower WHC values than CaCl₂ solutions in the control but not in the HTC beans. WHC values in control beans tended to increase with higher IS, although this effect was not as apparent for HTC beans.     

NONENZYMATIC LIGNIFICATION OF ASPARAGUS?

The hypothesis of nonenzymatic lignification was investigated in asparagus. Samples were stored within 2 h of harvesting at 22C, 4C and - IOC and tested daily, every second day and at 30-day intervals, respectively. Some asparagus was blanched at IOOC for 3 min prior to storage. Assays for peroxiduse and polyphenoloxidase showed no enzymatic activity in the blanched samples. Toughness, as measured by Warner-Bratzler shear force, and crude fiber content (mechanically separated) significantly (P< 0.05) increased in both blanched and unblanched samples over the testing period at all storage conditions. Crude fiber content and shear measurements were significantly (P < 0.05) higher for the enzyme active controls. Microscopic examinations using light (LM) and scanning electron microscopy (SEM) were canied out to locate the site of lignin deposition and to quantify the extent of lignification. Sections viewed using LM techniques were stained to observe useful fluorescence (crystal violet - erythrosin B) and differentiate ligniped from nonlignified cell walls fast green safranin and crystal violet - ertythrosin 8). In samplesfrom each treatment and storage condition, three independent techniques indicated a significant (P < 0.05) increase in: (1) the width of the mechanical tissue layer; (2) the thickness of the cell walls of the cells comprising the mechanical tissue layer, and; (3) the thickness of the xylem vessel walls of the vascular bundles. Also, significant (P C 0.05) differences were detected between the extent of lignification of unblanched and blanched samples. These data suggest that a nonenzymatic "toughening" mechanism does occur in blanched asparagus tissue and that it may be related to lignin deposition.     

SENSORY AND OBJECTIVE EVALUATION OF A RESTRUCTURED BEEF PRODUCT

A study was undertaken to determine the effect of connective tissue, flake size and NaCl level on the texture of restructured beef steakettes; to examine the effect of these factors on the acceptability of restructured steakettes; and to develop sensory and instrumental texture profiles of the product. Restructured beef steakettes were manufactured with two levels of connective tissue (high, low), three flake sizes (3 mm, 6 mm, 13 mm) and three NaCl levels (0.25%, 0.50%, 0.75%). The textural attributes of these products were measured by a trained sensory panel and by objective measures of compression texture profile analysis, Warner-Bratzler shear and three tensile tests. Most sensory texture attributes could be predicted accurately using instrumental methods. Reduction of the sensory attributes by Principal Components Analysis revealed two underlying dimensions of connective tissue and bind strength. A consumer panel rated steakettes manufactured with 6 mm flakes and 0. 75% NaCl at either connective tissue level to be the most acceptable of the 18 products manufactured for this study.     

LIGNIFICATION: EVIDENCE FOR A ROLE IN HARD-TO-COOK BEANS

An investigation was undertaken to establish whether lignification was a possible mechanism contributing to the hard-to-cook defect in beans (Phaseolus vulgaris). Cell wall material (CWM) from control and defective beans was isolated and microscopic techniques employed to compare the two fractions. Transmission electron microscopy indicated that potassium permanganate-fixed material had heavier deposition of manganese dioxide in cell corners, secondary walls and middle lamella of hard beans, a pattern seen during the lignification of plant tissue. CWM from hard beans had a lamellated appearance not seen in the control as viewed by scanning electron microscopy. It is suggested that this is a result of cellulose deposition, a process known to occur before lignification. This tentative evidence of lignin within the cell walls of legume seeds has a host of implications for hydration during cooking, cell separation and ultimately, texture.     

PREDICTION OF DROP SIZE IN PULSED PERFORATED-PLATE EXTRACTION COLUMNS

A single expression for the prediction of drop size in the mixer-settler, transition and emulsion regimes of operation in pulsed perforated-plate liquid/liquid extraction columns is presented. Analysis of 326 published drop size measurements both with and without mass transfer for 16 liquid/liquid systems from 12 different data sources show that the Sauter mean drop diameter, d ₃₂, in the dispersion is given in terms of column geometry, operating conditions and physical properties of the phases by:

in which ρ_* and σ _* are the density and surface tension of water at 20°C and α and 1 are the fractional plate free area and compartment height respectively. This equation predicts the drop diameter with an average deviation of 11·3% which is much better than the average errors obtained using other available correlations.     

IMPLICATE FINAL CAUSES IN DEVELOPING MATERIAL SYSTEMS

Abstract

Causality in changing natural systems can be seen to involve all four Aristotelian causal categories—material, efficient, formal and final. Final causality of materialistic origin can be found in the need to maintain energy flow continuity within dissipative systems. Each interacting dissipative system acts finalistically so as to attract needed energy. In so acting, it continually disturbs its neighborhood by generating potential energy flow disruptions as results of its activities. Final causality based, in this way, on the energy requirements of dissipative systems will generate formal causes as well. In contrast, the emergence of formal causes in mechanistic systems driven solely by efficient causes is extremely unlikely. We suggest viewing the subordination of phenotypic dissipative systems by genotypic counterparts as an historical example of the emergence of formal causes out of the material necessity of maintaining flow continuity. Functional separation between genotypic and phenotypic dissipative systems can occur if the energies to be dissipated are localized, as is the chemical binding energy of molecules with respect to biological functions at a higher scalar level.