Comparison of Conventional and Microwave Baked Bread Concerning Recrystallization of Starch Molecules

K Fuckerer,J Rumpf,H Langer,N Leitschuh,J.J Schmitt,C Rosenberger,A Elsen

doi:10.19026/ajfst.9.2000

Abstract

Bread is one of the most important foods in industrial countries and it is at its best when consumed fresh. One of the major problems during storage of baked products is staling. Bread staling incorporates a combination of physical and chemical changes resulting in a decrease of bread quality. The predominant mechanism of staling is the time-dependent recrystallization of starch molecules. Avoiding this recrystallization is one of the most desired topics in science of bread technology but still not solved. Therefore, this study investigates a new possibility by trying to influence the recrystallization of starch with microwave heating. For this, the differences between microwave and conventional baked rye-wheat bread were examined concerning the difference of water activity and firmness of the bread during time. As result, a faster water loss during storage period could be observed in microwave heated bread, which probably implies an even more rapid recrystallization instead the desired avoiding of recrystallization of starch.

Highlights

The bread underlies physical and biochemical changes during the baking process such as volume expansion, denaturation of proteins, gelatinization of starch, crust formation and redistribution as well as evaporation of water (Sablani et al, 1998)
After baking special attention is given to the starch, because it is the reason for the typical rearrangement of bread characteristics during storage time of bread
Molecules rearrange towards the oscillating microwave field, which leads to a rotating friction between the water molecules

Summary

INTRODUCTION

The bread underlies physical and biochemical changes during the baking process such as volume expansion, denaturation of proteins, gelatinization of starch, crust formation and redistribution as well as evaporation of water (Sablani et al, 1998). The close bound of the crystalline starch structures results in firmness and hardness of the crumb (Schiraldi and Fessas, 2001) In this investigation the recrystallizing behaviour of starch in brown bread (rye-wheat bread) was researched under different heating mechanisms. Palav and Seetharaman (2007) hypothesized that the microwaves vibrate the water molecules present in the crystalline regions of the starch, thereby the lamellar arrangements of amylopectin crystals are destroyed. This occurs before the system reaches gelatinization temperature and probably fragments the granule at higher temperatures. As within convection heating oven, provide enough time for starch gelatinization to pass through its different phases, like starch swelling, loss of birefringence, amylose leaching and granule folding (Palav and Seetharaman, 2007)

MATERIALS AND METHODS

RESULTS

DISCUSSION

CONCLUSION