(1998). Edible Films and Coatings: Tomorrow's Packagings: A Review. Critical Reviews in Food Science and Nutrition: Vol. 38, No. 4, pp. 299-313.

Edible Films and Coatings: Tomorrow's Packagings: A Review

Partial dewatering and direct formulation of food pieces can be obtained by immersion in concentrated solutions. This process, known as osmotic dehydration or dewatering and impregnation soaking process (DIS process), can be used as a pretreatment before any complementary processing, and may lead to energy savings and quality improvement. To date, industrial applications of the process have mainly been limited to semi-candied fruit production lines, the control of which has mostly been empirical. Recent advances in the control of mass transfer have opened up the way for optimization of the process and the development of new applications, which have, in turn, triggered off new research areas for the years to come. These are mainly related to the management of concentrated solutions and the microbiological validation of the process.

Recent advances in the osmotic dehydration of foods

Osmotic dehydration in fruit and vegetable processing

Osmotic dehydration, due to its energy and quality related advantages, is gaining popularity as a complimentary processing step in the chain of integrated food processing. Generally, osmotic dehydration being a slow process, there has been a need for additional ways to increase the mass transfer without adversely affecting the quality. This gave the required motivation for many recent advances in this area. However, certain constraints still exist for the wide industrial adoption of osmotic dehydration, which need to be addressed in current and future research in the area. In order to compare the results of various investigators, there is a need to express research results in terms of more fundamental parameters like diffusion coefficient. Consequently, suitable methods to estimate such parameters in various foods of different size and geometry are discussed. The mechanism of osmotic dehydration proposed recently is described. Various methods to increase the rate of mass transfer, such as application of high hydrostatic pressure, high electrical field pulses, ultrasound, vacuum and centrifugal force are also presented.

Recent developments in osmotic dehydration: methods to enhance mass transfer

The oil palm tree is an ancient tropical plant that originated from West Africa. Palm oil has centuries׳ long use as food and medicine. This review covers the recent significant materials found in the literature on palm oil processing, refining, and use in frying especially in blends with other vegetable oils. Crude palm oil (CPO) is obtained from the fruit of the oil palm tree (Elaeis guineensis). The oil is rich in palmitic acid, β-carotene and vitamin E. CPO has been fractionated mainly into liquid palm olein and solid palm stearin in order to diversify its food applications. Palm oil is highly stable during frying especially due to the synergistic activity of β-carotene and tocotrienol. In recent years there has been a shift from the use of animal fats and hydrogenated vegetable oils in frying and other food applications. The use of naturally stable oils such as palm oil and composite oils like blends of palm oil and other fats and oils is practiced to ensure that maximum benefits are derived from the oils. Blending offers functional, nutritional and technical advantages, such as tailoring the oil to suit frying applications. The objective of this review is to combine and condense the body of research on the processing, characterization and use of palm oil especially in frying as well as suggest areas that need further research.

Palm oil: Processing, characterization and utilization in the food industry – A review

Agar model gel cubes, with initial low solute content, were soaked in higher concentration solutions. The influence of the concentration and molecular weight of the solute in the soaking solution, the temperature. the agar and solute content of the model food on water loss and solute gain rates were observed. The achievement of a prevailing dewatering effect with only marginal solute pick-up proved to be related to a inverse relationship between the cross-flows of water and solute, reinforced by shrinkage. As a preliminary to further modelling, reasonable assumptions were drawn from experimental result analysis.

SIMULTANEOUS WATER AND SOLUTE TRANSPORT IN SHRINKING MEDIA - PART 1: APPLICATION TO DEWATERING AND IMPREGNATION SOAKING PROCESS ANALYSIS (Osmotic Dehydration)

Mass transfer phenomena were qualitatively investigated during osmotic dehydration of fresh apple in concentrated solutions using response-surface methodology. the influence of the main process variables (solute concentration, solute molecular weight, temperature and processing time) were thus determined. Osmotic phenomena, such as plant cell plasmolysis, only had a marked effect on dehydration at moderate temperatures (T > 50°C) and when low molecular weight solutes that could easily penetrate tissues were used. More generally, basic dehydration mechanisms were diffusive and seemed to be closely correlated with the formation of dense solute barrier at the surface of the product. the formation of this barrier layer, which was promoted by high molecular weight solutes and/or high solute content, could reduce loss of natural fruit solutes.

Mass transfer phenomena during osmotic dehydration of apple II. Frozen plant tissue

Characterization of heat and mass transfer during deep-fat frying and its effect on cassava chip quality

Simultaneous dewatering and salting of cod fillets was achieved by soaking them in mixed concentrated solutions (sucrose/salt or corn starch syrup/salt) at low temperature. Water loss, sugar gain and salt gain kinetics, as well as sugar/salt interactions were studied. The results showed how the presence of sugar can enhance water loss, and hinder salt entrance. The use of high molecular weight sugar prevented sugar entrance and allowed a good dehydration. These results revealed that this operation is particularly interesting as an alternative to traditional cod processing. In fact, process duration can be reduced, water loss and salt entrance better controlled.

Anne-Lucie Raoult-Wack

Papers

Recent advances in the osmotic dehydration of foods

SIMULTANEOUS WATER AND SOLUTE TRANSPORT IN SHRINKING MEDIA - PART 1: APPLICATION TO DEWATERING AND IMPREGNATION SOAKING PROCESS ANALYSIS (Osmotic Dehydration)

Mass transfer phenomena during osmotic dehydration of apple II. Frozen plant tissue

Characterization of heat and mass transfer during deep-fat frying and its effect on cassava chip quality

Dewatering and Salting of Cod by Immersion in Concentrated Sugar/Salt Solutions