TREE STRUCTURES OF LINEAR THRESHOLD UNITS FOR THE CLASSIFICATION OF NUMERIC EXAMPLES

A decision tree-based system for learning from numeric data is described. Results from linear algebra (pseudoinverse matrices) help the system to generate decision trees where the nodes are represented by linear threshold units minimizing the mean square error. The system's capability to provide good classifications with small decision trees is demonstrated on artificial and benchmark data.     

The effect of coagulant type on yield and sensory properties of semihard cheese from laboratory‐, pilot‐ and commercial‐scale productions

Using calf rennet or a commercial microbial rennet substitute derived from Rhizomucor miehei cheesemaking experiments were performed at laboratory and pilot scale, and at commercial scale in two industrial dairy plants during regular production. At all levels of scale, the solids transfer from milk to curd was significantly higher (0.50–1.19%) when using calf rennet. There were significant differences in levels of proteolysis during maturation and in levels of bitterness at 12 weeks of ripening between Gouda cheeses produced with calf rennet or with commercial rennet substitute at pilot and at commercial scale.     

CONSTANT STRAIN RATE COMPRESSION OF BIOPOLYMER GELS

Usually, uniaxial compression of food materials is performed at constant speed, which causes an increase of the true strain rate during experiments. By using a method described previously (Jaros and Rohm 1994) highly elastic biopolymer gels were compressed at standard conditions and with decreasing crosshead speed in order to maintain constant strain rate conditions during test. In the case of gels showing failure at a Hencky deformation of > 0.5-0.6, significantly lower values for apparent fracture strain were found in constant strain rate compression. Differences in stress at apparent fracture showed good agreement with respect to this critical value. Implications and consequences on interrelation between sensory and instrumental measurements as well as on relationships between rheological and fracture properties are discussed.     

Effect of Mineral Gluconates on Quality Characteristics of Bread and Cookies

These studies examined the effect of expanded fortification (FNB, 1974), using gluconates of Fe, Zn, Ca, and Mg as the mineral source, on quality characteristics of white pan bread and chocolate chip cookies. Gluconates, including magnesium gluconate, did not affect the yeast activity, dough mixing time, proof time, or dough pH. The pH and subjective quality scores of the breads were also little affected by any of the gluconates. Fortification reduced the specific loaf volumes slightly and also caused, by day 6, a greater firming of the crumb. Gluconates did not affect the subjective quality scores or spread ratios of the cookies, although cookie pH was lowered somewhat. Used singly, test gluconates did not appreciably alter the bread or cookie flavor profile except that cookies containing Zn gluconate were consistently preferred.     

Recent advances in milk clotting enzymes

Coagulating enzymes are an absolute necessity for the production of ripened cheese varieties. The objective of this review is to summarise and interpret the latest findings for the most important types of enzymes, which are animal rennet, genetically engineered chymosin, coagulants of microbial origin, and plant‐derived clotting enzymes. Special emphasis has been placed on aspects of enzyme chemistry and technology, selected methods for the analysis of coagulants, and the impact of the enzymes on proteolysis, cheese yield and cheese quality.     

TRANSGLUTAMINASE IN DAIRY PRODUCTS: CHEMISTRY, PHYSICS, APPLICATIONS

Literature on the effects of microbial transglutaminase on various dairy‐based systems is discussed. Beginning with a short synopsis on the development of microbial transglutaminase as a functional tool for modifying foods, the principles of reactions catalyzed by transglutaminase and their structural implications, as well as the mechanisms of formation and cleavage of isopeptide bonds are reviewed. After summarizing the present knowledge on the specificity of microbial transglutaminase towards milk proteins, including reactions determined by individual lysine and glutamine residues, emphasis is placed on the effects of enzymatic cross‐linking on physicochemical properties in foods and, particularly, dairy‐based systems. Discussed are implications of cross‐linking on acidified milk gels including yogurt and effects on single milk protein fractions, with respect to several physicochemical properties including rheology and mechanical properties of these systems, but also syneresis, and emulsification behaviour.     

THE USE OF SORGHUM (SORGHUM BICOLOR L. MOENCH) DHURRINASE-ENRICHED PREPARATION IN THE DETERMINATION OF TOTAL CYANIDE IN SORGHUM AND SORGHUM PRODUCTS

A dhurrinase (sorghum β-glucosidase II) which catalyzes the hydrolysis of dhurrin (p-hydroxy-L-mandelonitrile β-D-glucoside) was purified 87-fold from sorghum seeds using acetone precipitation, bentonite adsorption and column chromatography on hydroxyapatite and DEAE-cellulose. Dhurrin, the natural substrate for this β-glucosidase, was used for enzyme assay. Dhurrinase, as opposed to alkali hydrolysis of dhurrin for cyanide assay, proved to be more efficient in releasing free assayable cyanide (CN^-) during the determination of total cyanide in sorghum and sorghum-derived products.