Navin K. Rastogi

Opportunities and Challenges in High Pressure Processing of Foods

Consumers increasingly demand convenience foods of the highest quality in terms of natural flavor and taste, and which are free from additives and preservatives. This demand has triggered the need for the development of a number of nonthermal approaches to food processing, of which high-pressure technology has proven to be very valuable. A number of recent publications have demonstrated novel and diverse uses of this technology. Its novel features, which include destruction of microorganisms at room temperature or lower, have made the technology commercially attractive. Enzymes and even spore forming bacteria can be inactivated by the application of pressure-thermal combinations, This review aims to identify the opportunities and challenges associated with this technology. In addition to discussing the effects of high pressure on food components, this review covers the combined effects of high pressure processing with: gamma irradiation, alternating current, ultrasound, and carbon dioxide or anti-microbial treatment. Further, the applications of this technology in various sectors—fruits and vegetables, dairy, and meat processing—have been dealt with extensively. The integration of high-pressure with other matured processing operations such as blanching, dehydration, osmotic dehydration, rehydration, frying, freezing / thawing and solid-liquid extraction has been shown to open up new processing options. The key challenges identified include: heat transfer problems and resulting non-uniformity in processing, obtaining reliable and reproducible data for process validation, lack of detailed knowledge about the interaction between high pressure, and a number of food constituents, packaging and statutory issues.

Recent developments in osmotic dehydration: methods to enhance mass transfer

Abstract 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.

Water and solute diffusion coefficients of carrot as a function of temperature and concentration during osmotic dehydration

Abstract Mass transfer was quantitatively investigated during osmotic dehydration of fresh carrot over a range of concentration (40–70 °B) and temperature (30–50 °C) of osmotic solution. Effective diffusion coefficients of water as well as sucrose were estimated using the solution of Ficks unsteady state law. Multilinear analysis of the estimated effective diffusion coefficients of water and solute revealed that these values depend upon temperature and concentration of the osmotic solution as well as the combined effect of temperature and concentration.

Mass transfer during osmotic dehydration of banana: Fickian diffusion in cylindrical configuration

Abstract Mass transfer during osmotic dehydration of banana has been studied. The solution of Ficks law for unsteady state mass transfer in cylindrical configuration has been used to calculate the effective diffusion coefficients over a range of temperature (25–35 °C) and concentration (40–70 °B) of osmotic solution. The effective diffusion coefficient has been empirically correlated with the concentration and temperature of osmotic solution by an Arrhenius-type equation. A high degree of correlation ( R 2 = 0.97) was observed between predicted and experimental values of the effective diffusion coefficient.

Opportunities and Challenges in Application of Ultrasound in Food Processing

The demand for convenience foods of the highest quality in terms of natural flavor and taste, and which are free from additives and preservatives, has spurred the need for the development of a number of non-thermal approaches to food processing, of which ultrasound technology has proven to be very valuable. Increasing number of recent publications have demonstrated the potential of this technology in food processing. A combination of ultrasound with pressure and/or heat is a promising alternative for the rapid inactivation of microorganisms and enzymes. Therefore, novel techniques like thermosonication, manosonication, and manothermosonication may be a more relevant energy-efficient processing alternative for the food industry in times to come. This review aims at identifying the opportunities and challenges associated with this technology. In addition to discussing the effects of ultrasound on foods, this review covers various areas that have been identified as having great potential for future development. It has been realized that ultrasound has much to offer to the food industry such as inactivation of microorganisms and enzymes, crystallization, drying, degassing, extraction, filtration, homogenization, meat tenderization, oxidation, sterilization, etc., including efficiency enhancement of various operations and online detection of contaminants in foods. Selected practical examples in the food industry have been presented and discussed. A brief account of the challenges in adopting this technology for industrial development has also been included.

Optimised production and utilisation of exopolysaccharide from Agrobacterium radiobacter

The cultural conditions for bacterial exopolysaccharide production by Agrobacterium radiobacter were optimised by response surface methodology (RSM) to maximise the viscosity of the broth and the yield of the polysaccharide. A study of complex interactions among sucrose concentration (0.5–5.5 g%), inoculum concentration (1–15%, v/v) and pH (4–8) was carried out using central composite design of experiments. The exopolysaccharide contained glucose, galactose and rhamnose (88.9:10.4:0.7) and formed an elastic gel on heating followed by cooling, at 2 g% concentration. The exopolysaccharide produced in a simpler inorganic nitrogen containing medium can be used as an emulsifier, viscosifier and also as a gelling agent in the preparation of microbiological media. The optimum conditions, which were obtained for maximum viscosity of the broth (105.64 mPas) and the yield of the polysaccharide (2.26%) were, sucrose concentration 2.62%, inoculum concentration 1.0% and pH 6.24.

Mass transfer during infrared drying of cashew kernel

The aims of this study were to determine the effects of temp. on infrared drying of cashew nuts and investigate mass transfer during this process. Cashew nuts with intact testa layer were dried in an infrared oven (far infrared source, 3-15 mum) at 100, 110 and 120C and moisture content was determined at different time intervals within the range 2.5-30 min. Moisture diffusion coeff. were estimated using a modified solution of Ficks unsteady state diffusion equation; cashew nuts were considered to have spherical configuration in the model. The Arrhenius equation was used to describe the dependence of effective diffusion coeff. on infrared drying temp. The proposed model provided accurate prediction of moisture content of cashew nuts at any given time during the drying process. An activation energy value of 28.7 kJ/mol was calculated for infrared drying of cashew nuts.

Effect of Selected Additives on Microencapsulation of Anthocyanin by Spray Drying

Microencapsulation of anthocyanin pigment present in Garcinia indica Choisy was carried out with maltodextrin of various dextrose equivalents (DE 06, 19, 21, and 33) and other additives such as gum acacia and tricalcium phosphate to enhance the stability of the pigment. The microencapsulated pigment containing 5.0% maltodextrin DE 21, 0.25% gum acacia, and 0.25% tricalcium phosphate was found to have lowest hygroscopic moisture content (4.38%), highest antioxidant activity (69.90%), and highest anthocyanin content (485 mg/100 g). The glass transition temperature was 44.59°C. The sorption isotherms for microencapsulated powder showed that the samples were stable up to water activity less than 0.43. The scanning electron microscope structures depicted that the particle size ranged from 5 to 50 μm with smooth spheres. Storage at 4°C increased the half-life twofold compared to that of the spray-dried product kept at ambient temperature (25°C).

Processing of Honey: A Review

Thermal processing of honey eliminates the microorganisms responsible for spoilage. Microwave heating, infrared heating, ultrasound processing, and membrane processing have been explored as alternatives to conventional heat processing. Microwave heating provides a rapid method for achieving the desired level of yeast reduction with reduced thermal damage. Infrared heating is not as rapid as microwave heating but desired results are achieved in a relatively shorter duration (3 to 4 minutes) compared to the conventional method. Membrane processing is an athermal process and very effective in the complete removal of yeast cells from honey. Microfiltration and ultrafiltration could be employed to produce enzyme-enriched honey besides clarified honey.

Recent Trends and Developments in Infrared Heating in Food Processing

Fruit processing and preservation technologies must keep fresh-like characteristics while providing an acceptable and convenient shelf life as well as assuring safety and nutritional value. Processing technologies include a wide range of methodologies to inactivate microorganisms, improve quality and stability, and preserve and minimize changes of fruit fresh-like characteristics. Infrared (IR) heating offers many advantages over conventional heating under similar conditions, which include reduced heating time, uniform heating, reduced quality losses, versatile, simple and compact equipment, and significant energy saving. The integration of IR with other matured processing operations such as blanching, dehydration, freeze-dehydration, thawing, roasting, baking, cooking has been shown to open up new processing options. Combinations of IR heating with microwave heating and other common conductive and convective modes of heating have been gaining momentum because of increased energy throughput. A number of publications and patents have demonstrated novel and diverse uses of this technology. This review aims at identifying the opportunities and challenges associated with this technology. The effect of IR on food quality attributes is also discussed. The types of equipment commonly used for IR processing have also been summarized.