MULTIVARIATE ANALYSIS OF STRUCTURE-RELATED DATA TO EXPLAIN MILK CLOTTING ACTIVITY OF PROTEOLYTIC ENZYMES

Multivariate analysis was used for investigating the relationships between milk-clotting activity and physical/chemical properties, such as CD spectra, hydrophobicity and zeta potential, of ten proteolytic enzymes measured at six different pH values. Cluster analysis of CD data and zeta potential values classified the enzymes into five groups, i.e., three active enzyme groups and two inactive enzyme groups with respect to milk clotting activity. Classification of the enzymes into three groups, i.e., enzymes with high, medium and low milk-clotting activity, was achieved by discriminant analysis after adding the ratio of secondary structure parameters to the predictor variables. Results indicated that β-sheet, β-turn and random structure features were important for milk-clotting activity.     

Tetrathionate Protects Proteolytic Activity of Simulated Papaya Latex and Crude Papain

Sodium tetrathionate (TT) was assessed for its possible protection of proteolytic activity (PA) of rehydrated crude papain during drying and storage. The addition of 1% TT significantly decreased the loss of PA of rehydrated crude papain after being oven dried at 55°C. This protection of PA was 15–20% higher than that from metabisulfite. Crude papain with 1% TT lost 20% of PA and with metabisulfite lost 45% of PA in 13 wk at room temperature. Results suggest TT may decrease loss of PA during papaya latex processing and storage of crude papain.     

NONPARAMETRIC DISCRIMINANT ANALYSIS OF STATIC HEADSPACE VOLATILES FOR GRADING FRESH PACIFIC SALMON1

Whole pink salmon were iced and stored under refrigerated conditions to allow decomposition to occur. After sensory grading, static headspace volatiles were analyzed and 22 of them were retained for multivariate analysis. Principal component analysis indicated that most of the variation. (86. 5%) was carried in the first four dimensions. Six compounds received high loadings for the second principal component that was associated with quality grade variation. When used in the computation of nonparametric Epanachnikov kernel functions, ethanol and 3-methyl-1-butanol played an effective role at segregating grades A, B, and reject with a high rate of correct classification (95.6%).     

Elimination of β-Lactoglobulin from Whey to Simulate Human Milk Protein

When the pH of cottage cheese whey was adjusted to 4.5 in the presence of 6.7 mM FeCI³, β-lactoglobulin was eliminated from the whey as a precipitate. However, the majority of immunoglobuhns were also coprecipitated. To recover immunoglobulins together with α-lactalbumin, the whey pH was adjusted to 3.0 in the presence of 4.0 mM FeCI³. After centrifugation of the whey, the supernatant contained exclusively β-lactoglobulin; other whey proteins were found in the precipitate. Excess Fe₊₊₊ in the precipitate was removed by ion exchange or by ultrafiltration. This protein concentrate had a protein composition much more similar to that of human milk whey than that of ultrafiltered whey protein concentrate.     

Preparation of Colorless Globin from Bovine Hemoglobin using Sodium Alginate

Colorless globin was obtained from bovine blood hemoglobin using alginate. The optimum conditions for the globin separation were found to be pH 2.25; 0.348% NaCl and 0.107% alginate by the random centroid optimization. The response used for minimization was heme color divided by protein contents in the supernatant after heme precipitation. The protein recovery was 65% with 97.6% heme eliminated.     

Simple Separation of Immunoglobulin from Egg Yolk by Ultrafiltration

A water-soluble fraction (WSF) was prepared by filtering 10 times diluted yolk (pH 5.0) stored at 4–6°C through Whatman No. 52 or No.1 filter paper for delipidation. However, solid-phase delipidation using an octadecyl column after filtration through a cellulose powder column was more practical for industrial application. After ultrafiltration (UF) of the WSF (pH 9.0,1.5M NaCl), results showed: Amicon 80–85% recovery, 74–99% purity; Harp 72–74% recovery, 81–84% purity; A/G 75% recovery, 89% purity; Koch 88% purity.     

SECONDARY STRUCTURE OF SOME ASPARTYL PROTEINASES

A structural study of some aspartyl proteinases was undertaken. Secondary structure prediction methods indicate that chymosin, pepsin, penicillopepsin and Mucor miehei proteinase have relatively high proportions of β-sheet with active site aspartic acid residues located in β-turn regions. Secondary structure determination from far-UV CD spectral data support the above finding that the aspartyl proteinases have a high proportion of β-sheet. The proportion of β-sheet generally decreased at pH values greater than 6.3. More extensive unfolding occurred with pepsin and penicillopepsin than chymosin, Mucor miehei proteinase, Mucor pusillus proteinase and Endothia parasitica proteinase in the neutral to alkaline pH range. Results obtained from the near-UV CD spectra of the aspartyl proteinases indicate a change in spectra in the neutral to alkaline pH range which suggests the importance of aromatic groups to tertiary structure stability.     

Application of the Integrated Diode Synchronous Motor to Traction Drive Motors

In this study, a traction drive electric motor was designed with a new magnet‐free motor design technique where electromagnets are generated on a rotor by utilizing changes in the spatial second harmonic of the magnetic fields. To apply the proposed technique to electric motor design, balancing the rotor and stator magnetomotive force is important. This paper presents design methods for adjusting the rotor and stator magnetomotive forces. A test motor was designed with these design methods and evaluated using a motor bench. The analytical and measurement data indicated that the proposed motor performed comparably to magnet motors.