Formulation, chilling and freezing of foods through low temperature soaking processes

Direct contact chilling and freezing in a concentrated aqueous solution (AF) consists in soaking foodstuffs into chilled aqueous solution

Réfrigération et congélation par immersion dans des milieux réfrigérants : revue et tendances futures

International audienceImmersion contact chilling and freezing (ICF) in aqueous refrigerating media consists of soaking foodstuffs in a cooled aqueous solution. Binary brine solutions (sodium chloride, calcium chloride) are usually used, and less frequently ternary or more complex solutions such as water+salt+ethanol or water+sugars. The advantages claimed for ICF include shorter processing times, consequent energy savings and better food quality. This freezing technique nevertheless has a limited range of applications as it is not yet fully developed, in particular because of the problem of uncontrolled penetration of solutes into the food material. Recent advances in ICF process involve a detailed understanding of multicomponent mass transfer during soaking processes and solution properties at low temperatures. These advances should be of practical benefit, opening the way for new applications in the chilled and frozen food sector. The present paper comprehensively reviews the current state of the art and analyzes new prospects for the ICF process.La réfrigération et la congélation par immersion dans des milieux réfrigérants aqueux consistent en le trempage des aliments dans une solution aqueuse refroidie. Les solutions les plus souvent utilisées sont des solutions salines binaires (chlorures de sodium et de calcium). Plus rarement, on emploie des solutions ternaires ou des solutions plus complexes telles que eau+sel+éthanol ou eau+sucres. Les avantages revendiqués du procédé sont : un temps de traitement plus court, des économies d'énergie et l'obtention d'aliments d'une meilleure qualité. Cependant, les applications de cette technique de congélation sont limitées, car son développement est encore en cours ; la pénétration aléatoire des solutés dans des aliments est un problème qui reste à résoudre. Une approche qui consiste à élucider le transfert massique de plusieurs composants lors du trempage et les propriétés des solutions à basse température a permis récemment de progresser dans le domaine de réfrigération par immersion. Ce progrès devrait avoir des retombées pratiques qui ouvriront la voie aux applications nouvelles dans le secteur des aliments réfrigérés ou congelés. Cet article passe en revue la technologie de pointe actuelle et analyse les perspectives du procédé

Soaking in concentrated aqueous solutions for chilling, freezing and direct formulation

When chilling and freezing a product by direct contact with a low freezing point aqueous solutions (NaCl+water, CaCl2+water etc...) at low temperature, simultaneous heat and mass transfers take place. To date, mass transfer remained uncontrolled and stalled the development of the process. We carried out a preliminary experimental study of simultaneous heat and mass transfer over time on gels immersed in binary NaCl solutions and we studied the effect of the solution concentration/temperature on these transfers

Immersion chilling and freezing: a promising process for chilling, freezing and-or formulating

Direct contact chilling and freezing in a concentrated aqueous solution consists in soaking foodstuffs into a chilled aqueous solution

Comportement thermique et matière de la surface des produits alimentaires surgelés par immersion

International audienceThe aim of this work was to verify whether the existence of an impregnated, non-frozen surface layer of a product was theoretically possible during immersion freezing. A simple model of heat and mass transfer in a porous medium was developed for this purpose. The equation system was solved analytically for the time interval before the product starts to freeze. Two dimensionless groups, representative of the interaction between heat and mass transport during the initial moments of treatment, were identified. These numbers estimated for real foods are close in value to those of a glass bead bed which for this point-of-view, can get the status of model food. Simulations carried out on the glass bead bed also clearly demonstrated that there is a surface layer which does not freeze. The existence of such a layer in foodstuffs treated by immersion freezing would explain the persistence of high impregnation observed even after the formation of a freezing front.L'objectif de ce travail est de vérifier si pendant la congélation par immersion d'un produit, l'existence d'une couche superficielle imprégnée et non congelée est théoriquement possible. Pour ce faire, un modèle simple de transferts de chaleur et de matière au sein d'un milieu poreux est développé. Le système d'équations est résolu analytiquement sur l'intervalle de temps où le produit n'a pas commencé à congeler. Deux nombres adimensionnels, représentatifs de la compétition entre transports de chaleur et de matière, ont ainsi été élaborés. Les valeurs de ces deux nombres pour un aliment réel et un lit de billes de verre sont proches, et donc leur comportement thermique et matière au cours des premiers instants de traitement. Parallèlement, les simulations réalisées sur lit de billes de verre montrent clairement qu'il existe une couche superficielle qui ne congèle pas. L'existence de cette couche sur les aliments traités par RCPI permettrait d'expliquer la persistance d'une imprégnation forte même après la formation d'un front de congélation

Transport phenomena in immersion-cooled apples

International audienceThe effect of immersion chilling and freezing (ICF) process parameters (solution temperature, concentration and composition, initial food temperature) on heat and mass transfer, was studied on apple cylinders dipped into an NaCl aqueous solution, with particular emphasis on the unsteady state period (first hour of treatment). Food behaviour was characterized for various thermal processes ; levels of salt impregnation in chilling and supercooling conditions at 2°C and -10°C respectively were similar (3% i.m. after one hour of processing) and much higher than in freezing at -17,8°C (0,4% i.m. for the same processing time). Further control of solute entrance in freezing conditions could be achieved through food surface treatments including : precoating with cold water before ICF ; use of a complex immersion solution containing a high molecular weight of solute ; quick freezing of the outer food layer. Above all, frozen water fraction inside the food was found to be an important factor governing solute entrance in freezing conditions

La congélation par immersion des denrées alimentaires

Immersion freezing of foodstuffs consists in diving the food into a liquid at low temperature (TLa congélation par immersion des denrées alimentaires consiste à plonger les denrées dans un liquide à basse température (

Water mediated phenomena in some multi-functional food processes

Extrait de documentVarious food processes aim at controlling water in solid foodstuffs in order to increase their stability and shelf-life. In most cases, the main objective is to reduce water content and/or change the state and activity of water in the food matrix. This can be achieved throughout partial removing of water, addition of water activity lowering agents, or freezing . Processes to do so include air drying (conventional or super-heated steam), cooking, deep-fat frying, candying, salting, osmotic dehydration, air-blast or immersion freezing (1, 2, 3, 4). During such processes, water may migrate throughout the food matrix as well as at the interface between the solid food and the surrounding fluid (gaz, liquid). Water migration can be induced by different mechanisms, including diffusion, osmosis, or flowing in the matrix pores. Water may also undergo phase change (evaporation, freezing). Depending on the way water migrates or changes phase, the evolution in the multi-component and multiphase food are different, and can be classified into three types: i) evolution of inner concentration, pressure or structure fields ; ii) evolution of physical and physico-chemical state ; iii) evolution of microbiological, biochemical, thermal or enzymatic reaction kinetics. The objective of the present paper is to show how the further understanding of the "water mediated " phenomena makes it possible to improve process control and food quality. This is illustrated by various examples, such as: i) control of oil absorption related to the creation of pores and structural heterogeneity during frying, induced by water migration mechanisms and pressure fields; ii) control of thawing phenomena or solute concentration in the food outer layer in osmotic dehydration and immersion freezing, related to the evolution of inner concentration fields and /or crystallisation phenomena ; iii) control of cracker colour, related to solute entrainment by water during baking

Soaking process in ternary liquids: Experimental study of mass transport under natural and forced convection

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