A D V E R T I S E M E N T
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Question:What ingredients can I add or processing steps can I take to improve my frozen dough products? Answer:Bakery products, including bread, are characterized by a relatively short shelf-life, and their deterioration is caused by a fast-developing staling process, in addition to mould growth. These shortcomings of bread led to the development of a manufacturing method for frozen dough. Frozen dough production usually employs a rapid, no-time dough method to minimize yeast fermentation during dough preparation. Freezing and storage of dough at -18�C generates a loss in bread quality reflected by lower loaf volumes, longer fermentation times, texture deterioration, weakening of the dough, less elasticity of the dough, decreases in yeast viability and decreases in the retention of gases (CO2). Ice crystallization seems to be the origin of dough weakening. The temperature history during storage has a large influence on the structure of ice crystals that might recombine due to temperature fluctuations. The decrease in yeast activity and the damage to the gluten network due to freezing are important phenomena that cause a decline in the baking performance of the frozen dough. Improvements to quality of bread from frozen dough can be made through modifications to ingredients and processing methods. Both the ingredients and processing conditions have a stronger influence on bread from frozen dough than on traditionally prepared bread. Ingredient Modifications Flour protein strength was found to be more important than flour protein content for optimum frozen dough quality. However, extra strong wheat flours may be detrimental to frozen dough quality because they will hold a higher amount of freezable water than strong flours. Doughs made with strong flours are generally resistant to freeze damage, but severe processing conditions, such as repeated freeze-thaw cycles, could significantly weaken dough structure. Flours with extremely long mixing times should be avoided since they promote excessive heat build-up due to the motion of the mixing blades, which is detrimental to the yeast cells. If weak flour is used, supplementation with vital gluten can improve loaf volumes and breadcrumb characteristics and reduce fermentation times. A 5-6% trehalose content was shown to be the maximum level for improvement of yeast freezing resistance. Trehalose is a sugar containing two glucose molecules that is used to stabilize organisms such as yeast during freezing or drying processes. The choice of yeast strain is also an important factor and a more cold-resistant strain should be sought. Some studies showed that the activity of compressed yeast was less than that of instant active dry yeast in frozen dough. Regardless of the type of yeast used, the level of yeast usage is generally increased for frozen doughs to reduce the fermentation time requirement. Also, a reduction in the amount of added water can improve bread characteristics. The addition of dough strengthening agents such as stearoyl lactylate (SSL) or diacetyl tartaric acid esters of mono- and diglycerides (DATEM) can reduce the weakening of the dough and loss of gas retention. In one study, DATEM, used in combination with guar gum, yielded breads with greater volumes than breads without additives. Ascorbic acid has also been used in combination with dough strengthening agents to achieve greater improvements in frozen dough quality. The addition of sodium caseinate has a similar effect on dough quality, as does the addition of a combination of DATEM and ascorbic acid. Many of these additives also improved the elasticity of doughs and the ability to retain their form during thawing, fermentation and baking. Processing Modifications The quality and stability of frozen dough is greatly influenced by the processing conditions used during production. Dough mixing, freezing method, freezing rate and frozen storage conditions are all important. The dough temperature after mixing is also important. The dough temperature of frozen dough is usually 2-7�C lower than for traditional breadmaking, and generally falls in the range of 19-22�C. This lower dough temperature minimizes yeast activity before freezing. Dough resting is also often avoided completely in frozen dough production to minimize yeast activation and fermentation before freezing. However, after the stress involved in mixing, the resting step plays an important role in relaxation of the dough prior to further processing. Therefore, a short dough rest period may be beneficial. The maximum yeast activity is usually obtained with slow freezing rates. Fermentation, prior to freezing, reduces the freezing resistance of yeast. Sheeting-molding conditions have no significant effect on the stability of the frozen dough whereas the dough shape is influential; round dough pieces yield less satisfactory bread than slab or cylinder shaped doughs. The best thawing method includes a stepwise temperature increase. This reduces condensation on the dough surface, which would result in spotting and blistering of the crust. It also prevents the start of proofing of the surface layers while the centre is still frozen. Baking studies showed that as the thaw time was increased, the volume of the resulting loaves increased. Therefore, a slow thawing time is optimum. Also, softer bread was produced from doughs thawed for longer times. It is generally accepted that as frozen storage time increases, the proof time requirement of the dough also increases. Therefore, it is important to conduct a controlled shelf life study of your product prior to marketing. The use instructions on the package will need to be optimized for consumer use based on changes that may occur over time.