Cet article est la synthese thematique d'une enquete menee recemment aupres de professionnels (industriels, fabricants et chercheurs) des industries alimentaires sur le theme de la reduction de la consommation d'eau et de la production d'effluents polluants, liee a ces operations. Sont presentees dans un premier temps, secteur par secteur, des donnees de consommations d'eau et de volumes d'effluents produits. Il apparait que de nombreuses procedures de travail et procedes de fabrication peuvent etre ameliores. La tendance doit aller vers une gestion de l'eau comme matiere premiere ou solvant recyclable faisant partie integrante de la rationalisation des procedes (economie d'eau, d'energie, de matiere). Cette gestion passe par la minimisation des rejets apres epuration, en particulier dans le cas de traitement des effluents, et le recyclage des flux aqueux et de matieres, soit directement dans le processus classique de fabrication, soit de facon degradee dans les processus connexes. De nombreux points d'amelioration sont precises et des axes de recherche sont proposes

Cet article est la synthese thematique d' une enquete menee recemment aupres de professionnels (industriels, fabricants et chercheurs) des industries alimentaires sur le theme de la reduction de la consommation d' eau et de la production d' effluents polluants, liee a ces operations. Sont presentees dans un premier temps, secteur par secteur, des donnees de consommations d' eau et de volumes d' effluents produits. Il apparait que de nombreuses procedures de travail et procedes de fabrication peuvent etre ameliores. La tendance doit aller vers une gestion de l' eau comme matiere premiere ou solvant recyclable faisant partie integrante de la rationalisation des procedes (economie d' eau, d' energie, de matiere). Cette gestion passe par la minimisation des rejets apres epuration, en particulier dans le cas de traitement des effluents, et le recyclage des flux aqueux et de matieres, soit directement dans le processus classique de fabrication, soit de facon degradee dans les processus connexes. De nombreux points d' amelioration sont precises et des axes de recherche sont proposes.

Ein beachtlicher Teil unserer Lebensmittel wird in der Lebensmittelindustrie, in Gross- und Kleinkuechen mit heisser Luft waermebehandelt. Nahrungsmittel sind oft hitzeempfindlich und veraendern ihre physikalischen, chemischen, stukturellen oder mikrobiologischen Eigenschaften waehrend der Hitzebehandlung. Dies beeinflusst sowohl die Qualitaet als auch den Naehrwert der entsprechenden Lebensmittel. Ferner ergibt sich oft ein Verlust an Wasser oder anderen Lebensmittelinhaltsstoffen. So betraegt der Wasserverlust beim Backen von Brot 15 bis 20 % und beim Kochen von Fleisch bis zu 30 %. Es werden die Mechanismen des Stoff-Transports, die Eigenschaften des Lebensmittels, die in diesem Zusammenhang von Bedeutung sind, sowie einige Beispiele fuer Qualitaets- und Naehrwertveraenderungen, die waehrend der Verarbeitung auftreten, diskutiert.

Differences in recognition of physical properties of food in food science and engineering and the influence of water on them were discussed. The physical properties, 'Bussei' in Japanese, can be usually defined in food engineering and physics as 'the physical quantities that characterize a substance and do not depend on the shape and size of the material'. There seem, however, to be other interpretations of the physical properties among food researchers and technologists. For example, some researchers such as food chemists and cooking scientists refer to the dynamic properties and the texture of foods as the 'Bussei', whereas others such as technologists in food companies refer to it as the physical characteristics of foods reflecting some physical phenomena in food manufacturing and preservation processes. Most of the latter two types of 'Bussei' are influenced by the size and shape of materials and are not, therefore, the true physical properties. The type of 'Bussei' useful for food researchers and engineers would, however, vary depending on the situation or problem to be solved. Physical properties of foods are used for several purposes: first, they are indispensable parameters in the engineering models for predicting the optimal conditions for food manufacturing; second, the inner structure or state of food materials can be estimated from the behaviors of some of their physical properties. For example, water interacts with many food components; and thus the amount and/or state of water considerably influences the physical properties of foods, for example, by causing a change in the dynamic properties during sol-gel transition and the glass-rubber transition by the plasticizing effect of water.

We examined the pasteurization effect of superheated steam containing micro-droplets of hot water (Aqua-gas, 115 deg C), superheated steam (120 deg C, 180 deg C) and hot water (100 deg C) to control Bacillus subtilis spores on the potato surface. Decimal reduction times of B, subtilis spores with the heating media were 2.8, 5.0, 6.3 and 6.8 minutes respectively. In case of the Aqua-gas, almost 90% of the spores were presumably washed away from the potato surface by condensed steam and the micro-droplets within 2.5 minute. After the condensation of the steam on the potato stopped, the potato surface was subsequently pasteurized effectively by the Aqua-gas since the surface was kept wet by the micro-droplets and it was heated with high temperature steam. To examine the pasteurization effect of actually cooking with these heating media, kakuni (boiled pork belly with soy sauce) and gyusuji (boiled beef tendon with soy sauce) were cooked using the Aqua-gas (115 deg C) , superheated steam (180 deg C) and a gas stove. The bacterial numbers of the food cooked with the superheated steam and the gas stove increased to more than 103CFU/g after 5 days of storage at 10 deg C. In contrast, the bacterial numbers of the samples cooked with the Aqua-gas were maintained at less than 300 CFU/g during storage.