Comparative study on the freeze stability of yeast and chemical leavened steamed bread dough

Effect of magnetic fields on the structure, properties, baking performance of frozen wheat dough at different frozen stage

As an emerging physical technology, magnetic fields have been used to improve the quality of frozen and refrigerated foods. This study compared the effect of applying a static magnetic field (2 mT) at different stages of freezing and storage on the quality of frozen dough. Results suggested that the magnetic field significantly impacted frozen dough quality. It not only prevented the formation of ice crystals during the pre-freezing stage but also inhibited ice crystal growth during the following frozen storage. This effect helped to maintain the integrity of gluten proteins and their adhesion to starch granules by preventing the breakage of disulfide bonds and the depolymerization of gluten macromolecules. It was also observed that yeast inactivation and glutathione release were reduced, resulting in improved air retention and air production capacity of the dough. This, in turn, led to a more appealing volume and texture quality of the finished bread.

Effects of freeze-thaw cycles on the quality of Hot-dry noodles: From the moisture, starch, and protein characteristics

Freeze-thaw cycles (FTC) could cause damage to food during storage. The effects of different FTC on Hot-dry noodles (HDN) in terms of quality, moisture, starch, and protein characteristics were studied. This study showed that FTC decreased the texture properties and water absorption of HDN. Meanwhile, cooking loss was significantly increased after FTC. The water content of HDN was decreased and water migration was increased during FTC. In addition, results showed that FTC destroyed the order structure and increased the crystallinity of starch in HDN. Under FTC, the disulfide bond of HDN was broken, the free sulfhydryl group was increased, and the electrophoretic patterns confirmed the protein depolymerization. The microstructure also showed that the gluten network became incomplete and starch was exposed outside the substrate. This study expounded the mechanism of HDN quality deterioration during FTC, which laid a foundation for the development and improvement of frozen and freeze-thaw noodles.

Enhancing water retention and mechanisms of citrus and soya bean dietary fibres in pre-fermented frozen dough

In recent years, the production of prepared and frozen foods has increased with economic development. However, during freezing, moisture migration forms ice crystals that damage food structure and reduce quality. This study investigates moisture migration changes in pre-fermented dough during frozen storage and effectiveness of Citrus fibre (CF) and Soya dietary fibre (SDF) on quality improvement. Pre-fermented frozen dough properties were evaluated at different freezing storage days with CF and SDF. Results showed frozen storage reduced water retention, converting deeply bound water to weakly bound and free water. Freezable water content increased significantly from 53% (fresh) to 56.95% (60d-control), forming disruptive ice crystals in gluten protein structure. SDF had superior water flow restriction compared to CF, preventing large ice crystal accumulation, enhancing water-holding capacity, and maintaining gluten protein structure. These findings lay a theoretical foundation for improving quality and industrial applications of pre-fermented frozen dough.

Metabolomic insights into the effect of chickpea protein hydrolysate on the freeze-thaw tolerance of industrial yeasts

The use of frozen dough is an intensive food-processing practice that contributes to the development of chain operations in the bakery industry. However, the fermentation activity of yeasts in frozen dough can be severely damaged by freeze-thaw stress, thereby degrading the final bread quality. In this study, chickpea protein hydrolysate significantly improved the quality of steamed bread made from frozen dough while enhancing the yeast survival rate and maintaining yeast cell structural integrity under freeze-thaw stress. The mechanism underlying this protective role of chickpea protein hydrolysate was further investigated by untargeted metabolomics analysis, which suggested that chickpea protein hydrolysate altered the intracellular metabolites associated with central carbon metabolism, amino acid synthesis, and lipid metabolism to improve yeast cell freeze-thaw tolerance. Therefore, chickpea protein hydrolysate is a promising natural antifreeze component for yeast cryopreservation in the frozen dough industry.

A comparative study of magnetic field on the maximum ice crystal formation zone and whole freezing process for improving the frozen dough quality

Magnetic field individually applied on the maximum ice crystal formation zone (MMF) and the whole freezing process (WMF) was compared to improve the quality of multiple freezing-thawing treated dough. All treatments showed that the breadmaking performances of magnetic field-assisted freezing were better than the conventional freezing. Especially, the WMF-treated breads exhibited higher resilience and lower firmness than MMF-treated breads. WMF treatment made dough remained a continuous and compact gluten-starch matrix while the starches and glutens got separated in MMF-treated dough. It could keep the gluten macropolymer from freezing-induced depolymerization with the decreased free sulfhydryl by 7.09% and more ordered secondary structure. WMF had positive effects on the homogeneous water distribution and high water-binding ability in frozen dough where the freezable water decreased from 32.47% to 30.77%. This comparative study of different freezing stages provided new insights into the better application of magnetic field on frozen dough-based food.

The Effect of Terminal Freezing and Thawing on the Quality of Frozen Dough: From the View of Water, Starch, and Protein Properties

Frozen dough is suitable for industrial cold chain transportation, but usually experiences temperature fluctuations through the cold chain to the store after being refrigerated in a factory, seriously damaging the product yield. In order to analyze the influence mechanism of temperature fluctuation during the terminal cold chain on frozen dough, the effects of terminal freezing and thawing (TFT) on the quality (texture and rheology) and component (water, starch, protein) behaviors of dough were investigated. Results showed that the TFT treatment significantly increased the hardness and decreased the springiness of dough and that the storage modules were also reduced. Furthermore, TFT increased the content of freezable water and reduced the bound water with increased migration. Additionally, the peak viscosity and breakdown value after TFT with the increased number of cycles were also increased. Moreover, the protein characteristics showed that the low-molecular-weight region and the β-sheet in the gluten secondary structure after the TFT treatment were increased, which was confirmed by the increased number of free sulfhydryl groups. Microstructure results showed that pores and loose connection were observed during the TFT treatment. In conclusion, the theoretical support was provided for understanding and eliminating the influence of the terminal nodes in a cold chain.

Empirical and Theoretical Bases of Good Steamed Bread Production

Chinese steamed bread (CSB) is a main staple food in China, accounting for 40% of wheat flour usage in China. Due to its health benefits, CSB is gaining popularity across the world. In this review, the effects of gluten proteins (particularly glutenins and gliadins) on the quality of CSB are summarized from the literature. Requirements of appropriate rheological parameters in different studies are compared and discussed. Along with the increasing demand for frozen storage food, there are obvious increases in the research on the dynamics of gluten proteins in frozen dough. This review also summarizes the factors influencing the deterioration of CSB dough quality during frozen storage as well as effective measures to mitigate the negative effects.

Effect of mulberry leaf polysaccharides on the baking and staling properties of frozen dough bread

BACKGROUND

Deterioration in frozen dough bread easily occurs in store, resulting in tremendous economic waste. Therefore, it is imperative to find natural additives to improve storage staling. The effects of mulberry leaf polysaccharides (MLP) were studied in terms of baking, retrogradation and microstructural aspects in frozen dough bread.

RESULTS

The incorporation of MLP improved the specific volume and reduced the hardness of bread during room storage, with 1% MLP showing the best results. The results of X-ray diffraction and Fourier transform infrared spectroscopy showed that crystallinity was decreased and the formation of double helical structure was inhibited with the incorporation of MLP. Meanwhile, the results of low-field nuclear magnetic resonance demonstrated that the addition of MLP was advantageous for retarding water migration and distribution, with reduced water loss. It can be seen intuitively from scanning electron microscopy that MLP improved the gluten network with a smoother and flatter system.

CONCLUSION

MLP improved the quality of bread during storage and delayed the degradation of internal structure, and can be used as an effective natural additive to improve the storage stability of baked food. 1% MLP showed the best results. © 2022 Society of Chemical Industry.

Effect of multiple freezing/thawing cycles on the physicochemical properties and structural characteristics of starch from wheat flours with different gluten strength

The physicochemical properties and structural characteristics of starches from three wheat flours with different gluten strength (S-YM20, S-ZM27, and S-ZM366) during freezing/thawing (F/T) cycles were studied. After F/T treatment, the damaged starch content of these three starches all increased, and the lowest increment of damaged starch content after 8 F/T cycles was S-ZM366; the most serious distribution of particle surface concave hole and fracture was S-YM20, followed by S-ZM27 and S-ZM366; additionally, the results of solubility, swelling power, thermal stability and pasting properties indicated S-ZM366 exhibited the strongest resistance to F/T cycles. The differences of freezing resistance among the three starches were possibly ascribed to the differences in compositions, crystallinity and microstructure among these three starches. This study provides theoretical contribution to the development of frozen dough industry from the perspective of wheat variety.

Frozen steamed breads and boiled noodles: Quality affected by ingredients and processing

Chinese steamed breads (CSB) and noodles are staple foods for many people. The production of frozen steamed products and boiled noodles has kept increasing. This is due to the increasing demand of ready-to-eat frozen food products from the market. Frozen storage significantly increases the self-life of the products and reduces the production costs. On the other hand, the freezing and frozen storage lead to quality loss of the frozen products. This review summarizes effects of freezing and frozen storage on diverse quality attributes (e.g., structural and textural properties) of frozen northern-type steamed breads and boiled noodles. Food safety of the frozen products related to the COVID-19 pandemic is discussed. To counteract the quality loss of the frozen products, suitable processing methods, selection of basic ingredients and uses of various food additives can be done. Research gaps to improve the textural, cooking and nutritional quality of frozen CSB and noodles are suggested.

Electroporation Assisted Improvement of Freezing Tolerance in Yeast Cells

Prolonged storage of frozen dough worsens the structure of thawed dough. The main reason is the inhibition of yeast activity. In this study we investigated applicability of pulsed electric field treatment for introduction of cryoprotectant into yeast cells. We showed that pre-treatment of cells suspended in a trehalose solution improves freezing tolerance and results in higher viability after thawing. Viability increased with rise in electric field strength (from 3 to 4.5 kV/cm) and incubation time (from 0 to 60 min) after exposure. Pretreatment resulted in lower decrease in the viability of thawed cells, viability of untreated cells dropped to 10%, while pre-treatment with PEF and trehalose tripled the viability.

Evaluation of nutrient profile, biochemical composition and anti-gastric ulcer potentialities of khambir, a leavened flat bread

Khambir is a leavened staple food among the native highlanders of Western Himalaya. It is prepared by sourdough fermentation of wheat flour with yeast (YAK) or buttermilk (BAK). Both types of bread were rich in carbohydrate, protein, dietary fiber, containing less fat and gluten, and enriched with lactic acid, vitamins, and minerals. The in vitro digestibility test showed a slow glucose-controlled release potential of khambir that reflected improved content of rapidly digestible starch, slowly digestible starch, resistant starch, and predicted glycemic index. The changes of crystallinity to amorphous structures of starch, content of protein and fatty acid, and accumulation of 17 major metabolites were evaluated through FTIR and GC-MS. The extracts of khambir alleviated cold-induced gastric ulcers in the animal model as it exhibited histoprotective and anti-inflammatory activities. This study demonstrated that the traditional leavened bread khambir is nutritious and can alleviate gastric lesions related to acute mountain sickness.

The effect of γ-[Glu](1≤n≤5)-Gln on the physicochemical characteristics of frozen dough and the quality of baked bread

This study was the first to examine the effects of γ-[Glu]_(1≤n≤5)-Gln (GGP, a taste enhancer; added at 0.5% or 5.0%) on the breadmaking using frozen dough. γ-[Glu]_(1≤n≤5)-Gln was produced using the method established in our research center. The addition of GGP at either level increased yeast viability, freezable water content and storage and loss moduli, decreased the free sulfhydryl content of dough during the frozen storage and freeze-thaw cycles, and improved the microstructure of frozen dough and texture of the baked bread. The addition of GGP at 0.5% led to a dough having the highest extensibility, and most complete and uniform starch-gluten network, and a baked bread crumb with the lowest hardness, best texture, and most uniform organization. These results indicated that GGP has great potential as a food-derived cryoprotectant/antifreeze agent for the baking industry.

Dynamic characteristics of dough during the fermentation process of Chinese steamed bread

The fermentation process is crucial to the production of Chinese steamed bread (CSB). In order to select suitable indicators as the basis for further research of establishing intelligent monitoring method for dough fermentation state, this study investigated the dynamic characteristics of dough during fermentation. Indicators included water mobility and distribution, starch-pasting properties, content of free amino acid (FAA), volatile organic compounds (VOCs) and electronic nose (E-nose) response value. Starch-pasting properties of dough and relaxation time (T₂₁, T₂₂) did not change significantly during the fermentation process (p < 0.05). The VOCs and FAAs of the dough had significant differences (p < 0.05) in different fermentation times, but no rule was established. The E-nose response value to headspace was most suitable to monitor the fermentation of dough. Principal component analysis (PCA) was performed on E-nose data from 75 samples and the results indicated that samples of different fermentation states were accurately classified.

Influence of Konjac Glucomannan and Frozen Storage on Rheological and Tensile Properties of Frozen Dough

The impact of various amounts of konjac glucomannan on the structural and physicochemical properties of gluten proteins/dough at different periods of frozen storage is evaluated in the present study. As frozen storage time was prolonged, the molecular weight and the free sulfhydryl content of gluten proteins and the tensile properties of frozen dough all decreased. The addition of konjac glucomannan reduced the variations in the structural and rheological properties of gluten proteins/dough. Frozen dough with 2.5% added konjac glucomannan showed the highest water binding capacity and retarded the migration of water. Scanning electron microscopy and differential scanning calorimetry results also revealed that adding konjac glucomannan reduced the cracks and holes in the dough and enhanced its thermal stability. The correlations between mechanical characteristics and structure parameters further indicated that konjac glucomannan could not only stabilize the structures of gluten proteins but also bind free water to form more stable complexes, thereby retaining the rheological and tensile properties of the frozen dough.