Effects of different cultivars and particle sizes of non‐degermed millet flour fractions on the physical and texture properties of Chinese steamed bread

Changes in the grain quality of foxtail millet released in China from the 1970s to the 2020s

Foxtail millet (Setaria italica (L.) P. Beauv.) is popular for its medicinal and edible properties and is an important strategic reserve crop for future complex climates. In this study, the genetic diversity of 5 representative foxtail millet genotypes released from the 1970s to the 2020s was examined for their appearance quality, nutritional quality, amino acid contents, culinary quality and aroma profiles. The trend of these indicators over the 60 years of cultivar release was revealed. The results revealed that the genetic gains of b*, yellow pigment content (YPC), breakdown viscosity (BD), setback viscosity (SB), and consistency (CS) were 0.45 %, 0.93 %, 0.34 %, -1.97 %, and - 0.68 %, respectively. The replacement of foxtail millet cultivars improved their appearance quality, culinary quality, and aroma and decreased their nutritional quality. Overall, a compensation effect exists between nutritional quality and organoleptic quality. The transitional foxtail millet variety has advantages over both the old varieties and modern varieties. Therefore, breeders need to focus on improving the nutritional quality of foxtail millet and utilize the quality advantages of the transitional variety in the future.

Comparative Genomics and Characterisation of the Role of Saccharomyces cerevisiae Respiration in the Fermentation of Chinese Steamed Bread

The genetic composition of Saccharomyces cerevisiae and its various phenotypes during fermentation significantly correlate to the quality of Chinese steamed bread (CSB). However, the systematic correlation between different S. cerevisiae and CSB has not been fully elucidated. Herein, we characterised CSBs prepared with 36 isolates of S. cerevisiae (designated S1-S36) to comparatively evaluate their correlations. CSBs 1, 2, 13, 21, 25 and 33 exhibited suitable total titratable acidity (TTA) values, pH values and large specific volumes. Texture analysis showed that CSBs 1, 25 and 33 exhibited higher springiness and cohesiveness values. CSBs 8, 25 and 33 exhibited low hardness, gumminess and chewiness values. At the micro level, CSBs 1, 25 and 33 showed a loose reticular structure with large holes and in which starch particles wrapped into gluten protein. Fifty-nine volatile flavour compounds belonging to six categories were determined in 10 selected CSBs, and CSBs 1, 25 and 33 contained more flavour and balanced substance categories. In addition, comparative genomic analysis revealed 33 non-synonymous mutations in the three strains with strong fermentation ability (S1, S25 and S33) and the three strains with weak fermentation ability (S18, S20 and S35) involving 19 genes, including: the respiration-related genes COS5, COS8 and COX10; the starch metabolism transcription factor MSS11; the general transcription factor SPT8; the cell aggregation-related gene FLO1 and the transporter gene SEO1. Other genes with different genotypes were also enriched in respiration-related gene ontology terms. These data offer preliminary experimental evidence regarding the application of S. cerevisiae S1, S25 and S33 in fermented foods derived from grains.

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.

Microbiota structure of traditional starters from around the Tai-hang mountains and their influence on the fermentation properties, aroma profile and quality of Chinese steamed bread

BACKGROUND

Steamed bread is a popular staple food in China, and the significant regional differences of the microbiota in traditional starters make the flavor and quality of steamed bread highly variable along with long preparation times. Therefore, analyzing the microbial flora of traditional starters and their influences on the flavor and quality may help to solve the problems mentioned earlier, and it may also be conducive to potentially meet consumer needs and permit industrialization of this traditional fermented food.

RESULTS

One hundred and thirty-two fungal and 50 bacterial species were identified in five traditional starters, each with a different dominant genus. The fermentation properties of dough showed that total titratable acid, dough volume and gas production increased and the pH decreased with fermentation time. The traditional starters improved the quality of Chinese steamed bread (CSB) including the crumb structure, specific volume and sensory attributes. Thirty-three aroma compounds with a VIP (variable importance for the projection) > 1 were identified as characteristic aroma compounds. The correlations among the microbiota, aroma and qualities of CSB showed a greater contribution from the bacteria, which was consistent with the predictions of metabolic pathways in the sequenced genomes.

CONCLUSION

The quality of CSB fermented with traditional starters was improved induced by their different microbial profiles, and bacteria made a greater contribution than fungus to the aroma and qualities of CSB. © 2023 Society of Chemical Industry.

Effects of coarse cereals on dough and Chinese steamed bread - a review

Chinese steamed breads (CSBs) are long-established staple foods in China. To enhance the nutritional value, coarse cereals such as oats, buckwheat, and quinoa have been added to the formulation for making CSBs. This review presents the nutritional value of various coarse cereals and analyses the interactions between the functional components of coarse cereals in the dough. The addition of coarse cereals leads to changes in the rheological, fermentation, and pasting aging properties of the dough, which further deteriorates the appearance and texture of CSBs. This review can provide some suggestions and guidelines for the production of staple and nutritious staple foods.

Significance of different milling methods on white proso millet flour physicochemical, rheological, and baking properties

Proso millet is a nutritious, sustainable, and gluten free food which is currently underutilized. They can be incorporated into the grain industry and provide much needed healthy alternatives. Efficient grinding method should be adopted for easy incorporation. This study aimed to investigate the effect of three different methods of grinding namely, roller milling (RM), pin milling (PM), and hammer milling (HM) on proso millet flour rheology and baking properties for food application. The milling flow sheet was developed toward the production of the quality whole grain flour. The particle size distribution of all the flours showed bi-modal distribution except for the RM flour. The PM produced the flour with the finest particles with geometric mean diameter of 82 μm. The study also revealed that starch damage in the PM flour (4.64%) was higher than RM (2.46%) and HM flour (2.51%). The nutritional composition was not significantly affected by different grinding methods. Pasting properties of the flour were also affected by the grinding method applied. Rapid Visco Analysis profile showed pin mill flour to have a higher peak viscosity (PV) (2,295 cP) compared to HM (2,065 cP) and RM flour (2,130 cP). Finally, this study demonstrated that the production of bread from proso millet flour with desirable quality and texture is possible. The grinding method did not affect the specific volume of bread loaves and C-cell characteristics. The specific volume of the breads ranged from 2.40 to 2.52 cm³ /g. This study will help in promoting and producing value-added proso millet food products with enhanced nutritional quality.

The relationship between ecological factors and commercial quality of high-quality foxtail millet "Jingu 21"

The commercial quality of foxtail millet grain (Setaria italica L.) includes appearance quality, functional quality, and cooking and eating quality, which directly determine whether consumers will purchase the product. We studied the relationship between ecological factors and commercial quality attributes of foxtail millet "Jingu 21" from twelve production areas. The results showed that altitude, latitude, and diurnal temperature range were negatively correlated with b*, total flavones content (TFC), setback (SB), consistence (CS) and pasting temperature (PTM), but positively correlated with L/B and breakdown (BD). In contrast, average temperature, average precipitation, average humidity, available nitrogen, phosphorus, and potassium had positive effects on 1,000-grain weight (KGW), b*, TFC, CS, and PTM and had a negative impact on L/B and BD. Climate factors had a greater effect on the commercial quality of foxtail millet than soil factors, and the influence of climatic factors was particularly obvious in the early and middle growth periods. The multivariate equation between ecological factors and the comprehensive score of foxtail millet commercial quality is Y = 1,159.745-4.496X₁ (altitude) + 19.529X₅ (≥10℃ effective accumulated temperature) - 166.327X₁₀ (organic matters). In conclusion, high temperature and precipitation are conducive to high quality appearance and the accumulation of functional substances, while a high diurnal temperature range and high soil nutrients are conducive to the formation of cooking and eating quality. The impact of ecological factors on foxtail millet quality is complicated and it is essential to select a cultivation site that is matched to the intended use of the foxtail millet being produced.

The dough-strengthening and spore-sterilizing effects of mannosylerythritol lipid-A in frozen dough and its application in bread making

Biosurfactants have been put into applications in breadmaking industry, while the effects of mannosylerythritol lipid-A (MEL-A) on gluten network of frozen dough, bread quality and microbial spoilage were firstly investigated in this study. Rheology and differential scanning calorimetry (DSC) analysis showed that MEL-A significantly improved the rheological properties of frozen dough and reduced the content of frozen water. Further experiments showed that MEL-A promoted the formation of aggregates by interacting with gluten protein, and strengthened the gluten network through molecular weight distribution measurement and microstructure observation, effectively avoiding the destruction of ice crystals. A series of bread assessments illustrated MEL-A improved the loaf volume, gas retention ability and textural property. In addition, MEL-A (1.5%) killed 99.97% of the vegetative cells of Bacillus cereus and 75.54% of the spores, and at the same time had a slight inactivation effect on yeast. These results indicate that MEL-A has broad application prospects in the baking industry and the storage stage of flour products.

Effects of Different Amylose Contents of Foxtail Millet Flour Varieties on Textural Properties of Chinese Steamed Bread

In order to improve the nutritional value and quality of steamed bread, and promote the industrial development of the whole-grain food industry, a texture analyzer was used to study the effects of cultivars of whole foxtail millet flour (WFMF) on the texture of Chinese steamed bread (CSB). Orthogonal partial least squares discriminant analysis (OPLS-DA) was also conducted. The addition of different cultivars of WFMF significantly altered the height–diameter ratio, specific volume, hardness, cohesiveness, gumminess, and chewiness of CSB (p < 0.05). Large amounts of foxtail millet flour significantly increased the hardness, gumminess and chewiness of the bread (p < 0.05), and the bread height–diameter ratio, specific volume, cohesiveness and springiness significantly decreased (p < 0.05). We screened sensory evaluation, chewiness, specific volume, and hardness as the signature differences in the quality components according to the variable influence on the projection (VIP) values. OPLS-DA could distinguish the addition levels of different samples.