Advances in present‐day frozen dough technology and its improver and novel biotech ingredients development trends—A review
Authors: Omedi Jacob O. , Huang Weining , Zhang Binle , Li Zhibin , Zheng Jianxian 
Published: November 2018

Background and objectives

In response to the need for product flexibility and fast response to consumer trends, research interest frozen dough technology has continued to increase since its inception in 1970s. Common categories of these products are prefermented, unfermented, and par‐baked frozen dough products, with widely known frozen dough products such as refrigerated cookies and brownies, sweet rolls, biscuits, dinner rolls, and pizza, sold “as if freshly baked” to the consumer. The underlying catalyst for the development and growth of the frozen dough products in the 1970s–1990s is closely related the development of improver technology and increased research efforts to improve frozen dough quality, thus a steady market growth in frozen dough products in the following. Despite increased popularity of frozen dough products, they are still faced with processing challenges such as reduced yeast activity and viability, damaged dough gluten–starch network, and alteration of individual dough components which are induced by freezing and frozen storage treatment. Therefore, increased research efforts by both industry and academic institutions have been vital in understanding and improving processing parameters as well as the end‐product quality of frozen bread‐dough products. This review provides an overview of the effect of ice crystal characteristics on water redistribution and major components (starch and gluten) and ingredient (yeast) during freezing and frozen storage of frozen bread‐dough systems. Additionally, advances in frozen dough improver technology such as use of hydrocolloids, ice structuring proteins, ice‐nucleating agents, and novel fermentation end products and enzymes that alter ice crystal characteristics to improve steamed bread frozen dough quality are suggested and discussed. In addition, due to the recent increase in popularity of frozen steamed products, they are used as a case study and some critical conditions for their processing were suggested.

Findings

Freezing and frozen treatment on key components. Gluten: Gluten protein quality is mainly indicated by gluten macropolymer depolymerization during freezing and frozen storage. In frozen steamed dough systems, SH groups, an indicator of S‐S bond disruption, increased in gluten but fluctuated in glutenin fraction during frozen storage. This invariably increases the molecular weight distribution of the glutenin subunits (HMW‐GS and LMW‐GS). Starch: Freezing and frozen storage induces granule structure re‐organization; decline in amorphous state coupled with increase in crystallinity as starch granule materials leach out influences the A‐ and B‐type granules differently. Yeast: Freezing and frozen storage treatment decreases yeast activity and viability in frozen dough systems; with the degree of damage related to the freezing conditions used (e.g., freezing rates, ice crystal size and location, and ice recrystallization) and ability to metabolize different molecules (e.g., glycerol, trehalose, proline, arginine). Despite loss in activity and viability, yeasts are comparatively advantageous to use than chemical leaveners in frozen steamed dough systems. The degree of damage can be related to the freezing conditions used and ability to metabolize different molecules. Hydrated frozen steamed dough: three water sources identified as rigid, confined, and bulk water are found in the dough matrix system and are redistributed differently through ice crystallization and recrystallization in dough, thus affecting component structure and functionality. Bulk followed by confined water crystallizes to ice during freezing. The freezing rate applied will also affect the ice characteristics, thus altering structure and functionality. Hence, studies on water redistribution induced by ice crystallization and recrystallization may give a deeper understanding in the search of solutions to preserve gluten in frozen dough. Improver and cryoprotective technology: Advances in additives improver technology such as the use of hydrocolloids, ice structuring proteins or antifreeze proteins, and ice‐nucleating agents and the use of novel biotech ingredients and enzyme technology were able to (a) increase yeast cell freeze tolerance and (b) enhance gluten and starch functional (rheological, thermal) properties during freezing and frozen storage treatment. Subsequently, the yeast cells in frozen dough have better fermentative capacity, resulting in improved end‐product quality in terms of higher specific volume, lower hardness, and increased shelf life.

Conclusions

This is attributed to the additives ability to alter ice crystallization and recrystallization characteristics in frozen dough. Knowledge on development of ice crystallization and recrystallization during freezing and frozen storage, respectively, is useful to enable optimization of freezing conditions and reduction in temperature fluctuations to maintain yeast viability and frozen dough quality.

Significance and novelty

This overview adds new knowledge and useful insights into (a) use of biotech ingredients for clean label technology in frozen dough and food industry, a consumer demand trend for clean label products, and (b) optimization of frozen dough processing and equipment technology for modern baking and food industry.