Effects of different storage temperatures and time on frozen storage stability of steamed bread.

BACKGROUNDS: This research intended to explore the effects of different frozen storage temperatures and time on the stability of steamed bread. The quality characteristics, moisture content and microstructure of steamed bread were determined after quick-frozen for 30 min at -32 °C and frozen storage at -6, -12, -18, -24 and -30 °C for 1-4 weeks. RESULTS: When the frozen storage temperature is lower, the moisture content, specific volume, pH and the strong bound water in the steamed bread increase, the water loss rate and the contents of freezable water, the weak bound water and free water decreased. With the extension of frozen storage time, the pH value and water loss of steamed bread first increased and then decreased, while the trend of water content was opposite. The specific volume, cohesion and elasticity of steamed bread decreased, while the freezable water content, hardness and chewiness increased. The bound water of steamed bread gradually migrated to free water. In addition, the longer the frozen storage time and the higher the temperature, and the more serious the damage to the microstructure was. CONCLUSION: The shelf life of steamed bread frozen storage at -12 °C could be up to 3 weeks, and the quality of steamed bread stored at -30 °C for more than 3 weeks was the best. © 2022 Society of Chemical Industry.

Effect of subfreezing storage on the qualities of dough and bread containing pea protein.

BACKGROUND: In this paper, -6, -9 and -12 °C were selected as subfreezing temperatures of dough containing pea protein based on the results of low-field nuclear magnetic relaxation time. The effect of storage at subfreezing temperatures on dough properties was then investigated and compared with sample storage at -18 °C. RESULTS: The pH value, springiness, resilience, cohesiveness of dough and sensory score of bread gradually decreased and the hardness and water loss rate of dough gradually increased with the extension of storage time. However, dough hardness, viscoelasticity and fermentation volume were maintained more effectively in subfreezing storage than in -18 °C storage. The subfreezing temperature could alleviate the damage of gluten network structure in frozen dough by ice crystals and was beneficial in maintaining the elasticity of gluten proteins. The network system of pea protein, gluten protein and starch granules in dough storage at -9 and -12 °C was more tightly connected and the microstructure was similar to that at -18 °C. There was no significant difference between the quality of bread made from the dough stored at subfreezing temperature and that stored at -18 °C for 1-6 weeks, and the preservation effect at -12 °C was closer to that at -18 °C. CONCLUSION: Subfreezing storage can keep the stability of dough containing pea protein close to traditional frozen storage (-18 °C), which provides a new method for storage and transportation of frozen dough. © 2022 Society of Chemical Industry.

Dietary intervention with sialylated lactulose affects the immunomodulatory activities of mice.

Four sialylated lactuloses [N-acetylneuraminic acid-α2,3-lactulose (Neu5Acα2,3lactulose), N-acetylneuraminic acid-α2,6-lactulose (Neu5Acα2,6lactulose), deaminoneuraminc acid-α2,3-lactulose (Kdnα2,3lactulose), and deaminoneuraminc acid-α-2,6-lactulose (Kdnα2,6lactulose)] were reported to modulate the immunity of mice. The influences of cytokine expression, cell immunity, humoral immunity, and nonspecific immunity were investigated in our study using several techniques. Analysis via ELISA showed that cytokine expression was induced by sialylated lactulose treatment consistently in the serum and spleen. Among the 4 tested sialylated lactuloses, Neu5Acα2,6lactulose performed the best, simultaneously and appropriately promoting the expression of proinflammatory and anti-inflammatory factors in the serum and spleen. Kdnα2,3lactulose showed the best antioxidant activity according to detection of the activity of superoxide dismutase, myeloperoxidase, peroxidase, and alkaline phosphatase. Flow cytometry revealed that only Kdnα2,3lactulose significantly boosted the CD3+ T lymphocyte ratio similarly to that of lactulose. Analysis of the hemolysin content to characterize humoral immunity revealed that Kdnα2,3lactulose notably increased hemolysin content compared with that in the control group. To evaluate the nonspecific immune effects of the 4 sialylated lactuloses, a fluorescence microsphere phagocytosis assay was used to analyze the phagocytosis of macrophages. Kdnα2,3lactulose still performed the best in enhancing the phagocytosis of macrophages, showing markedly increased phagocytic percentage and phagocytic index values compared with those in the control and lactulose groups. Comparing the differences of these 4 sialylated lactuloses in affecting immunity in mice revealed that Kdnα2,3lactulose had the best overall performance in influencing cytokine expression, cell immunity, humoral immunity, and nonspecific immunity. This study provides critical support for use of sialylated lactuloses as potential immunomodulators in foods.

Rheological and microstructural characterization of wheat dough formulated with konjac glucomannan.

BACKGROUND: This work aimed to investigate the effects of different levels of konjac glucomannan (KGM) on the thermomechanical and pasting properties, water distribution, gelatinization, texture, and microstructural characteristics of wheat flour and dough. RESULTS: The thermomechanical properties assessed with a Mixolab showed that KGM could increase the water absorption and degree of softening and decrease the stability time of wheat dough. In addition, wheat flour starch with KGM underwent significant (P < 0.05) gelatinization changes according to the rapid viscosity analyzer and differential scanning calorimetry results. These results demonstrated that KGM enhanced the thermal stability and anti-aging capacity of wheat flour. All doughs with KGM exhibited viscoelastic behavior but lower hardness and gumminess. Low-field nuclear magnetic resonance showed that water, with a tight binding force, migrated to the weaker binding forces in the dough. A noticeable disruption of the gluten network was observed at the highest level of KGM. However, an intermediate level of KGM addition (10 or 15 g kg-1 flour) still rendered dough with satisfactory properties. CONCLUSION: A certain amount of KGM could enhance the thermal stability and anti-aging ability of wheat flour, improve the viscoelastic behavior, and decrease the hardness and gumminess of dough. In general, the mixing of flour and dough with KGM addition of 10 or 15 g kg-1 flour was of good quality. © 2021 Society of Chemical Industry.

The Application of Flipped Classroom Combined With Locus of Control Analysis in Lean Entrepreneurship Education for College Students.

This paper aims to explore the status quo and basic laws of entrepreneurship education at the stage of social development in China, thereby providing a theoretical basis and practical guidance for the cultivation of innovative and entrepreneurial talents in colleges. First, a college entrepreneurship education model based on lean entrepreneurship theory and flipped classroom was established to provide the development of entrepreneurship education with a theoretical framework while improving the students' autonomous learning ability. Based on the theoretical basis of the influence of the locus of control on entrepreneurial motivation in the entrepreneurial process of college students, the students who participated in the basic education of entrepreneurship among the sophomores in the first semester of the 2018-2019 academic year of a college in Shanghai were selected as the research object. Then, the effect of lean entrepreneurship education under the flipped classroom mode was analyzed. Before the start of the entrepreneurial basic education course, there was no difference between the pretest scores of the research group and the control group students (P > 0.05). After the course, there was no difference between the posttest scores of the two groups of students (P > 0.05). It can be confirmed that, based on the flipped classroom education mode of halving the actual number of lectures by teachers, the effect of basic education on entrepreneurship for students is not different from the traditional teaching effect. Based on the flipped classroom mode, the number of people who have reached the level of "understanding" of the text target task is the highest, and the number of people who can reach the "comprehensive application" level of the high-order target is almost 0. It means that the realization of the high-order target still needs to be strengthened. Lean entrepreneurship education mode is based on lean iteration, which is conducive to promoting the development of entrepreneurship education in China. Therefore, the application of flipped classroom combined with locus of control analysis in lean entrepreneurship education for college students can ideally achieve the goal of deep learning, which is greatly significant for improving the effectiveness of entrepreneurship education.

Oral Contraceptive Use and Increased Risk of Stroke: A Dose-Response Meta-Analysis of Observational Studies.

Background: Oral contraceptive (OCP) use might increase the risk of stroke in women. We examined a possible dose-response relation between OCP use and the risk of stroke in young and middle-aged women. Methods: A retrieval of PubMed and EMBASE databases was performed. We selected observational studies that reported odds ratios (ORs) with 95% confidence intervals (CIs) for the risk of stroke in OCP users. A two-stage dose-response analysis was conducted using the random-effects model and the restricted spline model. Results: A total of 6 cohort studies and 12 case-control studies were included, which involved 2,143,174 participants and 11,661 cases of stroke including ischemic stroke (IS), hemorrhagic stroke (HS), and stroke of unknown origin. The pooled ORs of total stroke were 1.19 (95% CI, 1.16-1.23) for every 10-µg increment in estrogen dosage, 1.20 (95% CI, 1.05-1.37) for every 5-years increment in duration of OCP use, and 0.82 (95% CI, 0.68-0.98) for every 5-years increment in duration of OCP cessation. The ORs of IS were 1.20 (95% CI, 1.17-1.22) in estrogen dosage, 1.24 (95% CI, 1.04-1.49) in duration of OCP use, and 0.78 (95% CI, 0.67-0.92) in duration of OCP cessation. The ORs of HS were 1.10 (95% CI, 1.04-1.16) in estrogen dosage, 1.13 (95% CI, 0.93-1.36) in duration of OCPs, and 0.71 (95% CI, 0.55-0.92) in duration of OCP cessation. The pooled ORs of total stroke from prospective studies (1.12; 95% CI, 1.01-1.24) were lower than those from retrospective studies (1.30; 95% CI, 1.01-1.67). Conclusions: The higher estrogen dosage significantly increased the risks of total stroke, IS, and HS, respectively. The longer duration of OCP use significantly increased the risks of total stroke and IS, but its effects on HS risk were marginal. The longer duration of OCP cessation significantly decreased the risks of total stroke, IS, and HS, respectively. These findings affirm the contribution of estrogen dose and duration of OCP use to the increased risk of stroke, which may be critical for the instruction of OCP use and the prevention and management of cerebrovascular diseases.