Microwave-Osmotic Dehydration of Cranberries under Continuous Flow Medium Spray Conditions

Derek Wray,Hosahalli S Ramaswamy

doi:10.1155/2013/207308

Abstract

Microwave-osmotic dehydration of cranberries was evaluated under continuous flow medium spray (MWODS) conditions after some pretreatments. A central composite rotatable design was used with three input variables at five levels (temperature, 33°C–67°C; sucrose concentration, 33°B–67°B; and contact time, 5–55 min). Responses were moisture loss (ML), solids gain (SG), and weight reduction (WR) as well as color and texture parameters. The responses were related to process variables using response surface methodology and statistical analysis: each model was tested for lack of fit to assure nonsignificance (P>0.05) and each process variable was tested for significance (P<0.05 or P<0.0001). Temperature was found to have the most prominent effect as it was significant with all drying (ML, SG, and WR) and quality (hardness and chewiness) parameters, while contact time was found to be significant with ML and WR. Concentration wasn’t found to be significant for any response. Increasing skin pretreatment severity generally promoted SG but had little effect on ML. The exception was chemical peeling, which favored ML but had no effect on SG. Overall, MWODS enables food dehydration in a much faster period of time than conventional osmotic dehydration (COD), while specifically promoting moisture loss over solids gain.

Highlights

Dehydration is one of the oldest methods of food preservation and is still prevalent in the food industry. e main objective of the dehydration process is to remove moisture to a point where the product is microbiologically and enzymatically stable and limit product deterioration during storage [1]. ere is an interest in producing dried ingredients which can be incorporated into other products like breakfast cereals or baked goods
The halved berries provided nearly the same amount of moisture loss when compared to the whole berry. is is in contrast to Grabowski et al [23], who found that cutting the berries in half increased the moisture diffusion by about 100-fold when compared to the mass transfer through the cranberry skin and overall by about a 4.5% increase in moisture loss over the length of the process. ere are a few possible explanations for this change, including a smaller solution-sample contact area in a spray setup when compared to a traditional immersion setup. is is important when you consider the positioning of the cranberry halves under the spray head
E solids gain for the most part increased with the level of destruction to the skin. e lone exception is that halved berries accounted for less solids gain, on average, than the double scored samples, the variation is within the error

Summary

Introduction

Dehydration is one of the oldest methods of food preservation and is still prevalent in the food industry. e main objective of the dehydration process is to remove moisture to a point where the product is microbiologically and enzymatically stable and limit product deterioration during storage [1]. ere is an interest in producing dried ingredients which can be incorporated into other products like breakfast cereals or baked goods. E main objective of the dehydration process is to remove moisture to a point where the product is microbiologically and enzymatically stable and limit product deterioration during storage [1]. Osmotic dehydration (OD) represents a mild processing step in which texture is only moderately affected, nutritional value is well maintained, and the product quality, especially the color, can o en be enhanced throughout the process [3]. Since the plant cell wall does not represent a perfect membrane, there is usually a small leakage of low molecular weight substances such as vitamins, minerals, or organic acids which diffuse out of the cell along with the water [4]. Since the plant cell wall does not represent a perfect membrane, there is usually a small leakage of low molecular weight substances such as vitamins, minerals, or organic acids which diffuse out of the cell along with the water [4]. is last diffusion tends to be insigni cant in terms of mass balance but can be important in terms of quality aspects; it has been noted that anthocyanin content in cranberries a er OD was 10% less than in fresh berries [5]

Methods

Results

Conclusion