Moisture determination is one of the most important and most widely used measurements in the processing and testing of foods. Since the amount of dry matter in a food is inversely related to the amount of moisture it contains, moisture content is of direct economic importance to the processor and the consumer. Of even greater significance, however, is the effect of moisture on the stability and quality of foods. Grain that contains too much water is subject to rapid deterioration from mold growth, heating, insect damage, and sprouting. The rate of browning of dehydrated vegetables and fruits and of oxygen absorption by egg powders increases with an increase in moisture content.

Determination of Moisture

Progress in three areas has provided analytical methods and understanding to assist in migration testing for compliance with European Community Directives on food contact materials. A simple migration test has been developed to indicate whether or not a food makes fatty contact with plastics. This test is then used to guide the initial choice of appropriate food simulants. The Karl Fischer technique for water determination has been used to eliminate the need to humidity condition plastics in overall migration testing. This results in more rapid and more reliable migration testing. Finally, the stability of 'positive-list' monomers and other starting substances has been examined in food simulants. This identifies those substances which, for reasons of reactivity, may not be expected to survive a migration test and for which, therefore, migration testing as such is inappropriate.

Practical aspects of testing food contact materials for migration.

Karl Fischer titration has been used to eliminate the need to humidity-condition food contact plastics under test for overall migration into olive oil. The water content of the oil is measured before and after the migration test. This direct measure of the loss (or uptake) of water by the test plastic is then used in calculations of the overall migration. The use of Karl Fischer titration gives faster analysis with reduced labour input. The time savings varied from a few days to several weeks depending on the type of plastic. Karl Fischer titration is particularly useful in the high temperature testing of polar plastics where incomplete humidity conditioning can lead to erroneous results. The technique should be equally valuable when employing sunflower oil or the triglyceride HB307 in place of olive oil.

An improved olive oil overall migration test for plastics using Karl Fischer titration.

Les ceramides sont des lipides de la classe des sphingolipides issus de la N-acylation d’une base sphingoide par un acide gras. Ces lipides et leurs analogues suscitent un grand interet comme composants actifs dans les industries pharmaceutique et cosmetique. Parmi les biocatalyseurs capables de realiser la synthese de ce type de lipide, la lipase B de Candida antarctica semble etre l’enzyme la plus adaptee a la production de « pseudo-ceramides » a partir d’amino-polyols. Dans ce contexte, nous avons aborde l’etude de l’acylation de composes de type « amino-alcool »catalysee par la lipase B de Candida antarctica, en gardant a l'esprit une approche fondamentale afin d’elargir les connaissances actuelles sur ce sujet. La premiere partie de notre travail a ainsi traite de l’etude cinetique de l’acylation de composes monofonctionnels afin de determiner les mecanismes reactionnels et l’enantio selectivite de la lipase B de Candida antarctica pour les reactions de N-acylation et de O-acylation. Les parties suivantes de notre travail ont porte sur une etude structure-reactivite du substrat accepteur d’acyle et sur l’etude de l’influence du solvant utilise (solvant organique ou liquide ionique) afin de determiner les facteurs cles influencant la chimio selectivite et la regio selectivite de la lipase B de Candida antarctica lors de l’acylation de composes multifonctionnels de type « amino-alcool ». Finalement, a partir des connaissances acquises dans les differentes parties, nous avons developpe et optimise un procede de synthese enzymatique de « pseudo-ceramides » (O,N-diacyl aminopropanediols) mis en oeuvre en reacteur continu a « lit fixe ».

https://tel.archives-ouvertes.fr/tel-00823900/document

Etude de l'acylation sélective de composés multifonctionnels par voie enzymatique : Application à la synthèse de pseudo-céramides

http://link.springer.com/content/pdf/10.1007/978-94-009-1671-5_23.pdf

Engineering of/with Lipases

Les resultats obtenus permettent de proposer cette methode comme methode officielle. Application a l'huile de soja

J A Wijsman

Papers

Karl Fischer Determination of Water in Oils and Fats: International Collaborative Study