Wilfried Ooghe

Maintenance threonine requirement and efficiency of its use for accretion of whole-body threonine and protein in Atlantic salmon (Salmo salar L.) fry.

Eighteen groups of seventy Atlantic salmon (Salmo salar L.) fry (initial mean body weight 0.8 (sd 0.01) g) were fed on semi-purified diets containing graded levels of l-threonine (Thr) in 15 litres aquaria at a temperature of 14.5+/-1 degrees C. Doses of Thr represented 1, 31, 41, 51, 62, 72, 83 and 93 % of its ideal level for optimum protein deposition. Indispensable amino acids other than Thr were included in the same proportion (on a g/16 g N basis) as in the Atlantic salmon fry whole-body carcass. Following 36 d of feeding and a 36 h fast, fry were killed for whole-body protein and amino acid analysis. Weight gain (r2 0.98), protein accretion (r2 0.97), and Thr accretion (r2 0.97) were linear (P<0.01) functions of Thr intake. Slope of the Thr accretion regression line showed that the efficiency of Thr utilisation above maintenance was 76 %. At zero Thr intake, fry lost 5.4 mg Thr/kg body weight0.75 per d. The Thr maintenance requirement was 7.2 mg/kg body weight0.75 per d and the Thr requirement for growth was 66 mg for 1 g protein deposition. Increasing doses of Thr resulted in increased (P<0.05) concentrations of histidine and lysine, and decreased concentrations of isoleucine in whole-body protein. The maintenance need for Thr represented 13.4 % of the total need for Thr. The data suggest that efficiency of Thr utilisation above maintenance is constant at all levels of Thr intake between 1 and 93 % of the level required for optimum protein deposition.

Monitoring nutritional quality of milk powders: capillary electrophoresis of the whey protein fraction compared with other methods

Deterioration due to Maillard reaction, of milk powder upon storage was monitored by capillary electrophoresis, IEF, amino acid analysis and determination of furosine, HMF, browning index and available lysine. In comparison with these other methods, capillary electrophoresis of β-lactoglobulin, revealing a native and a modified fraction of this protein, proved to be a fast, easy and sensitive method for monitoring the quality of milk powders during storage.

Use of pattern-recognition display techniques to visualize the data contained in complex data-bases. A case study.

Automation and computer acquisition of data in analytical chemistry has meant that enormous amounts of data can be obtained. The analytical chemist is faced with the problem of bringing some order into these data, so that he can understand the relationships between the variables being measured and between those variables and the object of his research. This is particularly difficult when more than two variables are being measured. Indeed, when only one or two variables are measured the analyst usually makes graphs to explain what happens. When more tha two variables are measured, it is impossible to represent the data in two dimensions. The purpose ofthis article is to show that, in such a case, pattern-recognition methods can be used to visualize the data and therefore to gain insight into them. These methods can be called display methods. Instead of giving a lot of theory, this is demonstrated with a practical example: the authentification of the geographical origin ofwine. The classical methods for the chemical analysis of wines enable the major constituents, such as ethanol content, dry matter, acidity and mineral content, to be controlled. These parameters can be useful for the detection of adulterations, but do not help with the problem of the identification of wines according to their origin. Until now, such an identification has only been possible with sensorial evaluation by experienced tasters. As the characterization of wines according to origin is important, several investigators have attempted to solve the problem by multivariate characterization of wines. Wines are analysed for a number ofconstituents and the set ofobservations made on each wine sample constitutes a pattern. If the constituents that were analysed were appropriately chosen, wines from different origins would have different patterns--so these patterns may be used for classification according to origin. Motet et al. [1] and Scarponi et al. [2 and 3-] analysed samples of three groups of Venetian DOC wines for several inorganic parameters. On the basis of the patterns obtained, and with the use of multivariate statistical techniques, the three groups of wines could be reasonably well identified. Kwan et al. [-4] also proved that the characterization of wines on the basis of inorganic contents can be useful for assignment according to origin. Schreier et al. [5] made use of the concentrations of aroma constituents derived from the grapes: the six groups of German white wines that were involved in their study could be discriminated using multivariate techniques. When the same samples were characterized by their content ofyeast metabolites, the discrimination decreased considerably. It has been suggested that amino-acid patterns may be useful for the detection of adulterations of food products (orange-juice

Contribution to the determination of the fruit juice content of fruit juice beverages and syrups

ZusammenfassungHeutzutage bestehen für Chemiker keine unüberwindlichen Probleme den Fruchtsaftgehalt von Erfrischungsgetränken und Sirupen, die aus einer Fruchtsorte hergestellt sind, festzustellen, da die Kalkulationen auf entsprechenden und zuverlässigen Kriterien basiert werden können, die in den verschiedenen europäischen Ländern gelten. Jedoch müssen Beeinflussungen durch Leitungswasser oder Zusatz von Zucker und auch organischen Säuren in Betracht gezogen werden. Sollte jedoch mehr als ein Saft in unbekannten Proportionen vorhanden sein oder sollten andere Säfte, die zusätzlich Säure oder Farbe bringen, zugegeben werden, wird das Problem komplizierter. Um die Saftzusammensetzung feststellen zu können, muß man spezifische Parameter verwenden, um den Saftgehalt der Hauptkomponente kalkulieren zu können. Eine gute Hilfe die Saftzusammensetzung festzustellen, scheint die schrittweise Regressions-Analyse zu sein, die auf den Aminosäurewerten der acht Hauptaminosäuren basiert, welche in allen Säften vorhanden sind. Dieses recht theoretische Thema wird durch Kalkulationsbeispiele von Sirupen, Nektaren und Limonaden illustriert.SummaryNo insurmountable problems now face the food chemist in determining the fruit juice content of fruit juice beverages and syrups made from one species of fruit, since calculations can be based on relevant and reliable authenticity criteria and standards established in European countries. However, if the beverage contains more than one juice, or juice has been added to acidify or give additional colour, the problem is more complex. As a function of the juice exposition specific parameters are needed to calculate the juice content of the main component. Stepwise regression analysis, based on the relative content of the eight amino acids present in all juices, appears to be a useful method to determine the juice composition. This theoretical matter is illustrated here by examples of calculations of the fruit juice content of a syrup, a nectar and four lemonades.

Principal components analysis as a tool for the optimization of experimental conditions

Principal Components Analysis is used to display the variation in a data set consisting of the free amino-acid patterns in serum from dogs as a function of fasting time. Inhomogeneities found in the data set resulted in an optimization of the experimental conditions. Moreover important observations concerning sampling time and biological variability could be made.