Effect of storage conditions on the quality of frozen steamed bread

Effect of oxidized starch on the storage stability of frozen raw noodles: Water distribution, protein structure, and quality attributes

Freezing is a popular method of food preservation with multiple advantages. However, it may change the internal composition and quality of food. This study aimed to investigate the effect of modified starch on the storage stability of frozen raw noodles (FRNs) under refrigerated storage conditions. Oxidized starch (OS), a modified starch, is widely used in the food industry. In the present study, texture and cooking loss rate analyses showed that the hardness and chewiness of FRNs with added OS increased and the cooking loss rate decreased during the frozen storage process. Low-field nuclear magnetic resonance characterization confirmed that the water-holding capacity of FRNs with OS was enhanced. When 6% OS was added, the maximum freezable water content of FRNs was lower than the minimum freezable water content (51%) of FRNs without OS during freezing. Fourier-transform infrared spectroscopy showed that after the addition of OS, the secondary structures beneficial for structural maintenance were increased, forming a denser protein network and improving the microstructure of FRNs. In summary, the water state, protein structure, and quality characteristics of FRNs were improved by the addition of OS within an appropriate range.

Inulin with different degrees of polymerization as a functional ingredient: Evaluation of flour, dough, and steamed bread characteristics during freezing

In the study, the effects of short-chain inulin (OP), natural inulin (OH), and long-chain inulin (OHP) at substitution levels of 3%, 6%, and 9%, as well as freezing of 0, 15, and 30 days, on the farinograph and extensograph characteristics of flour, the rheological properties, water distribution, and microstructure of dough, as well as the quality of the final steamed bread, were investigated. The findings revealed that inulin led to a reduction in the water absorption of the dough while increasing its stable time. Furthermore, inulin delayed the alteration of freezable water within the frozen dough. Notably, the addition of inulin resulted in a more cohesive and evenly arranged network structure within the frozen dough. Steamed bread supplemented with 6% OP, 6% OH, and 3% OHP consistently dislayed a higher specific volume and spread ratio. These findings offer valuable insights into the utilization of inulin in frozen wheat foods.

Serratia marcescens Causes the Brown Discoloration of Frozen Steamed Stuffed Buns during Resteaming

Brown discoloration was observed in the crust of commercial frozen steamed stuffed buns (FSSBs) during resteaming. Culture-dependent and culture-independent analyses demonstrated that Serratia marcescens, a prodigiosin-producing species, was more abundant in spoiled samples than in unspoiled samples. Inoculation of experimental FSSBs with S. marcescens isolated from spoiled FSSBs confirmed that this species causes brown discoloration of FSSBs during resteaming. S. marcescens formed prodigiosin only between 15 and 28 °C but brown discoloration appeared only upon resteaming after storage at 4 °C. High-performance liquid chromatography analyses revealed that prodigiosin was absent from yellow-brown FSSBs. The pigmentation observed during resteaming is thus likely attributable to the intermediate 2-methyl-3-amylpyrrole. These findings provide valuable insights into the microbial contamination of FSSBs and will facilitate the prevention of spoilage of FSSBs.

Characterizing the Internal Structure of Chinese Steamed Bread during Storage for Quality Evaluation Using X-ray Computer Tomography

Chinese steamed bread (CSB) is a traditional food of the Chinese nation, and the preservation of its quality and freshness during storage is very important for its industrial production. Therefore, it is necessary to study the storage characteristics of CSB. Non-destructive CT technology was utilized to characterize and visualize the microstructure of CSB during storage, and also to further study of quality changes. Two-dimensional and three-dimensional images of CSBs were obtained through X-ray scanning and 3D reconstruction. Morphological parameters of the microstructure of CSBs were acquired based on CT image using image processing methods. Additionally, commonly used physicochemical indexes (hardness, flexibility, moisture content) for the quality evaluation of CSBs were analyzed. Moreover, a correlation analysis was conducted based on the three-dimensional morphological parameters and physicochemical indexes of CSBs. The results showed that three-dimensional morphological parameters of CSBs were negatively correlated with moisture content (Pearson correlation coefficient range-0.86~-0.97) and positively correlated with hardness (Pearson correlation coefficient range-0.87~0.99). The results indicate the inspiring capability of CT in the storage quality evaluation of CSB, providing a potential analytical method for the detection of quality and freshness in the industrial production of CSB.

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.

Impact of Different Frozen Dough Technology on the Quality and Gluten Structure of Steamed Buns

To advance the industrialization production of steamed buns, the current study explored the freeze-stability of unfermented, pre-fermented and par-steamed frozen dough. The results showed that the steamed bun made from unfermented dough with 2.0% yeast, the pre-fermented dough with a pre-fermented time of 30 min and the par-steamed dough with a pre-steamed time of 15 min showed the best sensory properties quality upon frozen storage. The gassing power of un- and pre-fermented dough gradually decreased, and dough with longer pre-fermented time exhibited more evident loss of gassing power. Freeze-induced depolymerization of gluten protein was the least distinct in the par-steamed dough, followed by the pre- and un-fermented dough, which was probably related to the superior freeze stability of glutenin-gliadin macro-crosslinks upon the pre-steaming stage. The surface hydrophobicity of gluten proteins of frozen dough decreased during the initial storage and was enhanced subsequently, which was related with the combined effects of the unfolding and synchronous aggregation induced by freezing and steaming, respectively. Moreover, the surface hydrophobicity of gluten in par-steamed frozen dough and steamed buns was more resistant to frozen storage, which was probably attributed to the established stable structure during the pre-steaming process.

Effects of different gelatinization degrees of starch in potato flour on the quality of steamed bread

The effect of four kinds of potato flour with different gelatinization degrees on the quality of steam bread was investigated in the present study. Results showed that medium-well flour (MWF) and potato flakes (PF) steamed bread, particularly MWF steamed bread, possessed the desired product properties liked by consumers. The MWF steamed bread had the highest appearance score (42.78) and total sensory evaluation score (81.60), and the PF steamed bread exhibited the highest specific volume (1.84 mL/g) and taste score (43.05). An increase in the degree of potato flour gelatinization led to an increase in dough gas retention coefficient from 80.20 mL/100 mL to 85.17 mL/100 mL and a more uniform and dense dough microstructure. During dough preparation, the increased gelatinization degree of potato flours enhanced the hydroscopicity competition between potato starch and gluten, resulting in a flocculent gluten network and increased potato starch volume during steaming. During steaming, steamed bread with higher gelatinization degree of potato flour formed a homogenous and dense starch gel-gluten double network, making them softer with more uniform gas cells and larger specific volume. Thus, this study provides a perspective of the effect of starch gelatinization on steamed bread quality.