USE OF SEMI-AUTOMATIC INSTRUMENTS FOR PROCESS AND PRODUCT CONTROL IN THE DAIRY-FOOD INDUSTRY

An integrated procedure for the rapid determination of total protein and heat treatment classification of skim milk powders by dye binding is described. Total protein values estimated by the Pro-Milk were in good agreement with the macro-Kjeldahl method; the correlation coefficient was +0–98 and the SD of the differences between the two methods was ±0.55, corresponding to a CV of ±1.52 per cent. Residual undenatured whey protein was measured by the Pro-Milk difference (PMD) method on undiluted isoelectric filtrates. These were prepared by addition of acetic acid - sodium acetate buffer to reconstituted skim milk powders. The undenatured whey protein levels thus determined correlated well with the ADMI Kjeldahl procedure. The reproducibility of the PMD method in our laboratory was ±0.010, and satisfactory reports on the reliability of the Pro-Milk procedure have been received from industry. It is recommended that future heat treatment classifications of milk powders should be based on dye binding. Furthermore, it is proposed that milk powders should be heat classified according to the percentage of undenatured whey protein to total protein in the reconstituted milk and expressed as the whey protein ratio (WPR) of the milk powder.     

Studies on the development of texturized vegetable products by the extrusion process.

Thiamin retention in extruded cowpea, mungbean, defatted soybean and air classified mungbean products was studied by a least squares regression equation using process temperature, screw speed, buffer pH and moisture content as the major independent variables. The increase in process temperature, pH and screw speed variables effected the decrease of thiamin retention values, while the increase in moisture content increased retention. The heat generation due to increase of stress force caused by increased screw speed presumably resulted in the thiamin retention values which were lower than expected. The carbohydrate and protein of the feed material flours pro-tected the thiamin during the thermoplastic extrusion process.     

Grain-Boundary Effect in Ceria Doped with Trivalent Cations: II, Microstructure and Microanalysis

Various samples studied for their electrical behavior in the previous paper are here examined in detail by microstructural and microanalytical techniques. While several microstructural features are observed, the presence of "thick boundaries" (an amorphous silica-rich phase that surrounds grain boundaries and forms a continuous network) appears to be the principal feature responsible for the grain-boundary effect. Such features are absent from samples prepared with nearly silicon-free materials, for which the grain-boundary effect is also virtually absent.     

Grain-Boundary Effect in Ceria Doped with Trivalent Cations: I, Electrical Measurements

The "grain-boundary effect," which leads to a greatly reduced dc ionic conductivity due to the presence of a blocking layer in the vicinity of the grain boundaries, is studied in detail for ceria ceramics doped with various trivalent dopants (particularly Y³⁺, Gd³⁺, and La³⁺). The effects of porosity, of sintering time, and of dopant size and dopant concentration are investigated. Finally, it is shown that the grain-boundary effect virtually disappears when nearly silicon-free starting materials are used.     

COMPOSITION OF CROCINS AND PICROCROCIN FROM SPANISH SAFFRON (CROCUS SATIVUS L.)

A method for simultaneous identification and quantification of crocins and picrocrocin by HPLC-DAD in aqueous extracts of saffron spice was used. The coefficients of variation obtained were lower than 10% for a majority of the crocins and picrocrocin. These substances are not found as standard compounds, for this reason it was necessary to obtain the response factor for each compound by collecting the fractions of each chromatographic peak and by using molar absorpitivity. This method can be used not only for crocins and picrocrocin determination but also for adulteration detection of saffron with water-soluble colorants. The method was applied to 260 samples of Spanish saffron, which came from the regions where saffron is an important crop, i. e., Castilla-La Mancha and Aragón. Spain is in the top group of saffron producers and Castilla-La Mancha is the largest saffron producing region in Spain. Four crocins and picrocrocin were ranked and the values used for differentiation according to origin. Only discriminant analysis could explain 100% of the variance by samples and location. The major discriminant variable was trans-crocin 4.     

Chemical Detoxification of Aflatoxin-containing Copra

Aflatoxin-containing copra at moisture contents of 24% and 7% was effectively detoxified by ammonium hydroxide (> 97% and 89% reduction, respectively). Detoxification was accomplished in 5 days using 1.5% ammonium hydroxide (ammonia/copra); in 10 days using 1.0% and in 15 days using 0.5%. The initial aflatoxin B₁ concentration of 500 ppb (9% moisture) was reduced to ≤ 20 ppb. Detoxification trials using a screw expeller showed 67% reduction in aflatoxin content of the oil with 1.0% ammonia.     

The preparation of protein hydrolysate from defatted coconut and soybean meals.

Protein hydrolysate prepared from defatted soybean meal and coconut meal using acid hydrolysis under different conditions were analysed and subjected to sensory evaluation. Analysis of amino acid after hydrolysis showed a 10.32% reduction in the soybean product and a 31.93% reduction in coconut product. Chemical analyses showed similarities in pH, viscosity, salt content and reducing sugar between the hydrolysates and the commercial soy sauce sample. Both amino and total nitrogen and acidity were higher in the hydrolysate than the commercial sample.
Sensory evaluation showed that hydrolysed soybean products gave better scores in terms of colour, aroma, flavour and general acceptability than coconut products. Addition of soybean to coconut meal resulted in improved hydrolysed product.     

The preparation of protein hydrolysate from defatted coconut and soybean meals

This study was conducted to determine the effects of temperature, time and concentration of acids on the hydrolysis of coconut and soybean meals. Using 6∼ hydrochloric acid (HCl), the complete hydrolysis of soybean meal was reached after 36 hr at 95°C, while it took only 24 hr to complete the process when 18 N sulphuric acid (H₂SO₂) was used at the same temperature. Coconut protein exhibited some degree of resistance to hydrolysis. Using 10 N HC1 and 18 N H₂SO₂ in two separate tests, it took 48 hr to complete hydrolysis at 95°C. Sulphuric acid caused a considerably greater decomposition of amino acids than HCl during longer periods of reaction with high acid concentration and temperature. Flavour development is a function of the free amino acids released which in turn is a function of acid concentration, reaction time and temperature.