CHAPTER 1 INTRODUCTION 1.1. Background Bread is one of the most widely-consumed food products in the world and breadmaking technology is probably one of the oldest technologies known. This technology has evolved continuously over the years as new materials, ingredients and equipment were introduced to produce better quality bread while various researches generated steady and impressive progress in breadmaking. The major ingredients for bread making are flour, water, salt, fat and sugars. Leavening agents (micro-organisms or chemical), improvers (e.g. stabilizer, emulsifier, oxidant, gums) and supplementary enzymes (e.g. exogenous α-amylase, protease, hemicellulase, lipase, lipoxygenase) are also frequently added (Gujral and Singh, 1999), meanwhile the word improver may be used as a very generic term for a wide range of additives used in bread formulation. Fresh bread typically presents an appealing golden brown crust, a pleasant roasted aroma, fine slicing characteristics, a soft and elastic crumb texture and a moist mouthfeel. Fresh bakery products, however, have relatively short shelf-life since during their storage, a number of physical and chemical changes occur, a process known as staling. The loss of bread freshness is parallel to an increase in crumb hardness and a 1
decrease in flavour and aroma, leading to loss of consumer acceptance. Loss of moisture and starch retrogradation are accepted as two of the basic mechanisms in the firming of the crumb. These preservation problems, coupled with the complex processes involved in conventional breadmaking and increasing market demands, have led to the continuous search for efficient methods to produce superior bakery products while preventing undesirable changes and extending the shelf-life. The current trend in the baking industry is to use frozen dough to manufacture quality products because it can be quickly transformed into fresh baked products, eliminating the problems commonly associated with the need for bakers to work midnight or early morning to provide customers with fresh bread on a daily basis and the difficult transportation of baked goods from large automated bakeries. By storing the dough at subzero temperatures, dough can be kept for days, weeks or even months and baked whenever there is a demand for fresh bread. The advantages of frozen dough made it popular since three decades ago. However, continuous research has also become indispensable in this area due to disadvantages of frozen dough over the conventional baking. The quality of bread made out of frozen dough is influenced by dough formulation, as well as process parameters such as dough mixing time (Rouille et al., 2000), freezing rate, storage duration, and thawing rate (Mazur and Schmidt, 1968; Varriano-Marston et al., 1980; Inoue and Bushuk, 1991; Neyreneuf and Delpuech, 1993; Le Bail et al., 1998; Lu and Grant, 1999). These factors may act either independently or 2
synergistically to reduce yeast activity which results in reduced carbon dioxide (CO 2 ) production or to damage the gluten network which in turn results in poor CO 2 retention and poor baking performance (Lucas et al., 2005). The inclusion of improvers in bread formulation may overcome such problems associated with frozen dough. 1.2. Objectives The study aims to utilize two special types of improvers and their blends to improve and advance the frozen dough technology in order to produce high quality bread which exhibits minimum negative consequences of the frozen storage and superior baking quality whenever possible. The objectives of this study are: 1. To determine the effects of propylene glycol alginate (PGA), sodium alginate (SA) and their blends on breadmaking quality of frozen bread dough by baking thawed dough after various period of frozen storage; 2. To investigate the effects of frozen storage duration on the baking quality of bread made from frozen dough; 3. To compare the performance of PGA, SA and their blends with commonly employed dough improvers diacetyl tartaric acid esters of monoglycerides (DATEM) and sucrose ester (SE); 3
4. To make recommendations on the optimum improver, its level of usage, as well as the optimum frozen storage duration. 1.3. Thesis Overview The thesis is organized as follows. A literature review on the topics of breadmaking and frozen dough development will first be presented, followed by detailed elaborations on the effects of frozen storage on bread dough and bread quality. In particular, the effects of the storage condition on the dough and final bread in terms of the dough strength, dough structure, yeast survival and gassing power, bread quality and bread staling behaviour will be examined. The background of the dough additives which are used in this research, i.e. PGA, SA, DATEM, and SE will also be presented, together with published literatures on the usage of such additives in bread, predominantly in frozen dough. In the Materials and Methods chapter, the dough preparation method will be presented, as well as the method used to analyze the dough quality, i.e. farinograph testing. Upon baking, the final bread quality will also be analyzed in terms of its bake loss, bread specific volume, crumb moisture content, and crumb texture. The results of the research will be presented in the next chapter, together with detailed discussions on the effects of various dosages of the additives on non-frozen dough in order to predict their effects on dough stored under frozen condition. The 4
effects will be presented in terms of the farinograph analysis of the dough, as well as the baking quality and staling behaviour of the final baked bread. Properties of the bread as a function of the frozen storage duration will be examined in the subsequent chapter. Various dosages of the additives were used in the bread production and the baking quality of the bread was analyzed in terms of the bake loss, specific volume, crumb moisture content and texture. Finally, a conclusion of the research will be given, together with a recommendation on the optimum type and dosage of additives to be used in frozen dough in order to produce bread with superior quality as well as a recommendation for future research. 5