Effects of konjac glucomannan on the water distribution of frozen dough and corresponding steamed bread quality

Revealing the influence mechanism of pre-fermentation degree and storage temperature fluctuations on frozen steamed bread dough quality

This study investigated the effects of pre-fermentation degree and storage temperature fluctuations on the gas cells, gluten protein, rheological properties of frozen dough, and quality of steamed bread. Three pre-fermentation degrees and four fluctuating temperatures (-10 °C, 0 °C, 10 °C, and 25 °C) were used. The gas cell size increased with the pre-fermentation degree; however, the gas cells merged and ruptured during temperature fluctuations. Sodium dodecyl sulfate extraction protein content and free sulfhydryl content increased by 3.07 % and 33.62 %, respectively, in the medium pre-fermentation group at 25 °C compared with those at -10 °C. The maximum strain of dough increased as pre-fermentation degree and fluctuating temperatures increased. The specific volumes of steamed bread with medium pre-fermentation degree were 1.87 mL/g at -10 °C and 1.47 mL/g at 25 °C. In conclusion, higher temperature fluctuations exceeding the freezing point exacerbated the dough and steamed bread quality, particularly in high pre-fermentation degree dough.

Deacetylation enhances the structure and gelation properties of konjac glucomannan/soy protein isolate cold-set gels

This study aimed to investigate the effect of the deacetylated konjac glucomannan (DKGM), with varying degree of deacetylation (DD), on the physicochemical and structural properties of transglutaminase-induced soy protein isolate (SPI) cold-set gels. Compared with native konjac glucomannan (KGM), DKGM significantly enhanced the gel strength, water-holding capacity, and thermal stability of the composite gels, with DK3 (DKGM with 65.85 % deacetylation) showing the most significant improvement. The secondary and tertiary structures of SPI in the DK3 group were the most stable. Compared with the KGM group, the DK3 group showed a 58.32 % increase in hydrophobic interaction and a 37.98 % decrease in free sulfhydryl content. The microstructure results demonstrated that DK3 was uniformly dispersed within the SPI network, promoting the formation of a continuous and dense network structure. This was mainly due to DK3 having a moderate particle size and low viscosity. Therefore, DKGM with a moderate DD is conducive to forming a more ordered and dense gel network structure, imparting optimal gel performance to the SPI cold-set gel.

Pea-Protein-Stabilized Emulsion as a High-Performance Cryoprotectant in Frozen Dough: Effects on the Storage Stability and Baking Performance

The use of oil-in-water (O/W) emulsion has drawn increasing attention in the baking industry. Compared with some of the well-recognized functionalities, such as textural improvers and flavor carriers, its cryoprotective behavior in frozen dough has not been extensively investigated. Herein, this study reported a pea-protein (PP)-stabilized O/W emulsion with good freeze-thaw stability and evaluated its effectiveness as a high-performance dough cryoprotectant. Specifically, the emulsions were stabilized by 2, 3, and 4 wt% of PP (PP-2, -3, and -4, respectively) and incorporated into frozen doughs, whose cryoprotective effects were systematically evaluated in terms of dough storage stability and baking performance after 4 weeks of storage. Results showed that the frozen dough with PP-3 emulsion exhibited the most uniform water distribution and reduced content of freezable water as reflected by the results from differential scanning calorimetry and low-field nuclear magnetic resonance analyses. Moreover, the PP emulsion helped to maintain the integrity of the gluten network, thus enhancing the dough elasticity. Accordingly, the emulsion-added bread samples exhibited significantly improved loaf volume and textural properties (e.g., softness) and less baking loss. Our findings highlighted the potential of PP emulsion as a viable and high-performance dough cryoprotectant.

Effect of Adding Konjac Glucomannan on the Physicochemical Properties of Indica Rice Flour and the Quality of Its Product of Instant Dry Rice Noodles

Instant dry rice noodles have a broad market prospect due to their advantages of long shelf life, convenient transportation, and convenient eating, but there are still quality problems such as long rehydration times and poor eating quality. In order to improve the quality of instant dry rice noodles, the effects of konjac glucomannan (KGM) on the gelatinization characteristics, pasting properties, and rheological properties of Indica rice flour and the structure, food quality, and starch digestibility of instant dry rice noodles made of Indica rice flour were studied. The results showed that the starch gelatinization conclusion temperature and endothermic enthalpy of Indica rice flour were reduced by adding ≤ 3% KGM, the peak viscosity, valley viscosity, final viscosity, and setback value of Indica rice flour in the pasting process decreased with the increase in the KGM addition amount, and the pseudoplasticity, viscosity, and elasticity of Indica rice flour paste were reduced by adding > 1% KGM. When the KGM addition amount was 2%, the endothermic enthalpy, final viscosity, and setback value of Indica rice flour were 2.74 J/g, 2379.5 cp, and 961.5 cp, respectively. The instant dry rice noodles made of Indica rice flour had a looser microstructure after adding KGM, and its short-range ordered structure and double helix content were reduced by adding 1~3% KGM. When the KGM addition amount was 2%, the rehydration time of instant dry rice noodles was 290 s, which was shortened by 14.7%, while the texture and sensory quality remained unchanged, and the SDS content was reduced by 16.4% while the RS content was increased by 28.8%. Therefore, the physicochemical properties of Indica rice flour and the quality of its instant dry rice noodles can be improved by adding an appropriate amount of KGM. This study can promote the application of KGM in improving the quality of rice products.

Improvement of the freezing resistance characteristics of yeast in dough starter

Improving the freezing resistance of yeast in dough starters is one of the most effective methods to promote the healthy development of frozen dough technology. When the dough starter was composed of yeast, lactic acid bacteria and acetic acid bacteria, the microbial proportion was 10:1:5, and the ratio of wheat flour to corn flour was 1:1. The proline contents of the starters and the survival rates and fermentation capacity of yeast significantly increased compared with those of the starter composed of yeast and wheat flour only (P < 0.05). Laser confocal microscopy observation showed that the cell membrane damage of yeast obviously decreased. Low-field nuclear magnetic resonance method revealed that the water distribution state of starters changed. Adding corn flour and acetic acid bacteria to dough starter in appropriate proportions improves yeast freezing resistance.

Insight into konjac glucomannan-retarding deterioration of steamed bread during frozen storage: Quality characteristics, water status, multi-scale structure, and flavor compounds

Konjac glucomannan (KGM), a water-soluble hydrocolloid, holds considerable potential in the food industry, especially for improving the quality and nutritional properties of frozen products. This study explored the alleviative effect of KGM on the quality characteristics, water status, multi-scale structure, and flavor compounds of steamed bread throughout frozen storage. KGM significantly improved the quality of steamed bread by slowing down the decrease in water content and the increase in water migration while maintaining softness and taste during frozen storage. Notably, KGM also delayed amylopectin retrogradation and starch recrystallization, thus preserving the texture and structure of the steamed bread. At week 3, the microstructure of the steamed bread with 1.0 % KGM remained intact, with the lowest free sulfhydryl content. Additionally, heat map analysis revealed that KGM contributed to flavor retention in steamed bread frozen for 3 weeks. These results indicate that KGM holds promise as an effective cryoprotectant for improving the quality of frozen steamed bread.

Insights into the effects of frozen storage on the rheology, texture and in vitro digestibility of frozen Liangpi (starch gel food)

In this study, the effects of frozen storage on the rheology, texture and in vitro digestibility of frozen Liangpi and its internal influencing mechanism were investigated. The results showed that with increasing frozen storage time, the solid-like property proportion of frozen Liangpi gradually enhanced, and its hardness and chewiness gradually increased, and its springiness gradually decreased, while its digestion rate gradually slowed down. During frozen storage, the water fluidity of frozen Liangpi gradually enhanced, and its starch molecules rearrangement degree gradually deepened. Meanwhile, the squeezing on the structure of frozen Liangpi caused by ice crystals recrystallization gradually aggravated. Based on the above results, it could be speculated that starch retrogradation caused by ice crystals recrystallization was the critical reason for the changes in the rheology, texture and in vitro digestibility of frozen Liangpi during frozen storage.

Mitigating effect of fucoidan versus sodium alginate on quality degradation of frozen dough and final steamed bread

The impact of fucoidan (FD) and sodium alginate (SA) addition (0.3, 0.6, and 0.9 g/100 g wheat flour, dry basis) and freezing time on the rheology, water, structural characteristics of dough, and the quality of end steamed bread was explored in this study. The results showed FD was more effective in improving the textural characteristics of frozen dough compared with SA. Meanwhile, the freezable and free water content of SA dough were lower than those of FD dough, with the most pronounced effect observed at 0.9%. Adding SA increased the storage modulus, loss modulus, and disulfide bond content of the dough. The addition of FD induced a denser gluten protein network with fewer pores. Furthermore, the addition of FD reduced the hardness and chewiness of steamed bread and increased its specific volume and lightness. Overall, FD could alleviate the quality deterioration of frozen dough and the corresponding steamed bread.

Using salted egg white in steamed bread: Impact on functional and structural characteristics

Steamed bread has long been an important part of Chinese cuisine. This study investigated the effects of salted egg white (SEW) (5, 10, 15, and 20% w/w) on the quality of steamed breads. Findings revealed that SEW notably enhanced the bread's volume and texture, with a 20% inclusion significantly boosting water retention and rheological properties, albeit reducing bread's lightness. In addition, the H-bond absorption band intensity in the Fourier transform infrared spectroscopy (FTIR) analysis showed increased peak intensities with higher SEW levels, indicative of protein structure alterations. X-ray diffraction confirmed the presence of an amylose-lipid complex. Scanning electron microscope (SEM) and Confocal laser scanning microscope (CLSM) imaging depicted a smooth, consistent protein network with SEW addition. Consumer sensory evaluation responded favourably to the SEW15 steamed bread, suggesting its potential for food industry application. Overall, the study considers SEW an effective ingredient for improving steamed bread quality.

Improving the gel properties of Ficus pumila Linn. pectin by incorporating deacetylated konjac glucomannan

To improve the gelation behaviour of pectin, the effect of deacetylated konjac glucomannan (DKGM) with various deacetylation degrees (27.44 %, 44.32 %, 60.25 %, and 71.77 %) on the heat-induced gel characteristics of Ficus pumila Linn. pectin was studied. The hardness, chewiness, and adhesiveness of the gel increased as the degree of deacetylation increased from 27.44 % to 60.25 %, but decreased at 71.77 %. Additionally, DKGM addition resulted in higher apparent viscosity and non-Newtonian fluid behaviour in the composite gel. The incorporation of DKGM into the gel matrix strengthened the gel structure by promoting hydrogen bond formation and shortening relaxation time compared to the control. Scanning electron microscopy images revealed that the densification of the pectin gel network increased as the degree of deacetylation of konjac glucomannan rose from 27.44 % to 60.25 %, but then loosened when it exceeded 71.77 %. As the degree of deacetylation increased, the hydrophobic interaction between pectin and DKGM increased. Overall, the addition of DKGM effectively modulated the gel properties of Ficus pumila Linn. pectin, thus broadening its industrial application on different gel products.

Enhancing frozen dough quality: Investigating the impact of soy hull polysaccharide (SHP) on rheological properties and microstructure

The effects of SHP on the texture, rheological properties, starch crystallinity and microstructure of frozen dough were investigated. The efficacy of SHP in enhancing dough quality is concentration-dependent, with frozen dough containing 1.5% SHP exhibiting hardness comparable to fresh dough without SHP (221.31 vs. 221.42 g). Even at 0.5% SHP, there is a noticeable improvement in frozen dough quality. The rheological results showed that the viscoelasticity of dough increased with higher SHP concentration. What's more, XRD and SEM results indicated that the SHP's hydrophilicity reduces the degree of starch hydrolysis, slows down the damage of starch particles during freezing, and consequently lowers the crystallinity of starch. Additionally, CLSM observations revealed that SHP enhances the gluten network structure, diminishing the appearance of holes. Therefore, the physical, chemical properties, and microstructure of frozen dough with SHP demonstrate significant enhancement, suggesting SHP's promising antifreeze properties and potential as a food antifreeze agent.

High freeze-thaw stability of Pickering emulsion stabilized by SPI-maltose particles and its effect on frozen dough

Pickering emulsions with good freeze-thaw stability are essential in frozen food applications. This study developed a high freeze-thaw stabilized soy protein isolate (SPI)-maltose (M) Pickering emulsion and applied it to frozen doughs to investigate and reveal its impacts on the processing properties of the frozen dough. The results showed that after the freeze-thaw cycle, with a volume ratio of 1:2 of SPI to M, the appropriate amount of M changed the structure of SPI. This resulted in the Pickering emulsion prepared by the SPI exhibiting the least droplet coalescence and the best freeze-thaw stability. The results of dough rheological properties, textural properties, and binding capacity with water demonstrated that Pickering emulsions effectively inhibited the loss of gluten protein network structure in the dough after freeze treatment and increased the binding capacity of gluten proteins with starch and water in the dough. The best results were obtained with the incorporation of 3 % SPI-M high freeze-thaw stability, where the amount of bound water following three freeze-thaw cycles was 4.27 times higher than in doughs without Pickering emulsion. Overall, this study is significant for enhancing the freeze-thaw stability of Pickering emulsions stabilized by proteins and providing a new application route for Pickering emulsions.

Effects of konjac glucomannan with different degrees of deacetylation on the properties and structure of wheat gluten protein

The properties and structure of gluten protein with different deacetylation degrees of konjac glucomannan (KGM) were investigated, in an attempt to improve the quality of gluten protein in flour products. Results showed that deacetylated KGM (DKGM) could improve the textural properties and enhance the thermal stability of gluten protein. DKGM increased the water holding capacity and shortened the T2 relaxation time of gluten after removing some acetyl groups. As the deacetylation degree increased, the hardness and adhesiveness of gluten gels gradually increased, while the springiness decreased. In addition, the presence of DKGM promoted the conversion from free sulfhydryl to disulfide bonds and increased the β-sheet content in gluten protein. The low-deacetylation KGM decreased the surface hydrophobicity and fluorescence intensity of gluten protein, and the microstructures of gluten gels became more compact. Compared with gluten protein-KGM complex gel, the degradation temperature of gluten protein-DKGM complex gels was observed to increase by >3 °C. Overall, the low-deacetylation KGM was beneficial for improving the physicochemical properties and maintaining the network structure of gluten protein. This study provides valuable references and practical insights to improve gluten quality in the flour industry.

Freezing rate's impact on starch retrogradation, ice recrystallization, and quality of water-added and water-free quick-frozen rice noodles

The study evaluated the effect of freezing rate on the quality of water-added quick-frozen rice noodles and water-free quick-frozen rice noodles. Results indicated that the retrogradation enthalpy, relative crystallinity, freezable water content, and cooking loss of water-added quick-frozen rice noodles were higher than those of water-free quick-frozen rice noodles with increasing storage time. Furthermore, ice recrystallization accelerated the deterioration of the quality of the rice noodles, resulting in the enlargement of the pores within the rice noodles and the formation of many pores on the surface. This phenomenon was particularly evident in the rice noodles of Y-40 °C (freezing with water at -40 °C) and Y-60 °C (freezing with water at -60 °C). After 28 days of frozen storage, the hardness increased by 83.83 % for rice noodles of Y-20 °C (freezing with water at -20 °C), while the hardness decreased by 51.68 % and 45.80 %, respectively, for rice noodles of Y-40 °C and Y-60 °C. Consequently, the impact of the freezing rate on the quality of water-added quick-frozen rice noodles is more pronounced than that of water-free quick-frozen rice noodles. Moreover, a higher freezing rate can delay the deterioration of the quality of frozen rice noodles by postponing starch retrogradation and inhibiting ice recrystallization.

Cryoprotective effects and mechanisms of soybean oligosaccharides on the grass carp (Ctenopharyngodon idellus) surimi during frozen storage

BACKGROUND

Conventional cryoprotectant mixtures (sucrose and sorbitol) impart excessive sweetness and calories to surimi. Therefore, there is a need to explore alternative cryoprotectants with low sweetness and low-calorie content. The cryoprotective effects and possible mechanisms of soybean oligosaccharides (SBOS) on the frozen stability of grass carp (Ctenopharyngodon idellus) surimi were investigated during 120 days of frozen storage in a comparison with commercial cryoprotectants (4% sucrose and 4% sorbitol, w/w).

RESULTS

SBOS at 6-8% (w/w) and commercial cryoprotectants could restrain water mobility and reduce thawing loss of frozen surimi by increasing non-freezable water content. SBOS could maintain the structural stability of proteins by preventing sulfhydryl groups from being rapidly oxidized to disulfide bonds, retarding the reduction of the solubility, Ca2+-ATPase activity and α-helix content of myofibrillar proteins (MP), as well as hindering the increasing surface hydrophobicity of MP of surimi during 120 days of frozen storage. The introduction of SBOS increased the gel strength and water-holding capacity of frozen-stored surimi. Compared with commercial cryoprotectants, 8% SBOS was more effective in stabilizing protein structure, whereas it was slightly less effective with respect to ice-forming inhibition.

CONCLUSION

The results obtained in the present study suggest that 8% SBOS could be potentially developed as a new cryoprotectant for surimi as a result of its ice-forming inhibition abilities and protein structure stability. © 2024 Society of Chemical Industry.

Effects of sanxan on water and ice crystal status of salt free frozen cooked noodles during freeze-thaw cycles

This study compared four biocolloids (sanxan, xanthan gum, curdlan, and guar gum) in different concentrations to replace NaCl in improving the recooking quality of salt free frozen cooked noodles (SF-FCNs). Sanxan outperformed NaCl and other biocolloids significantly improving the firmness (21.0%), chewiness (63.5%), and toughness (15.4%) of SF-FCNs after 10 freeze-thaw (FT) cycles. The results of the freezing-thawing curves showed SF-FCNs had prior FT stability when sanxan was added at 1.2%. Subsequently, the result of differential scanning calorimetry and nuclear magnetic resonance revealed sanxan reduced the content and mobility of freezable water while increasing the content of bound water. The scanning electron microscope, mercury intrusion, and optical microscopy analyses indicated that sanxan reduced the size and volume of ice crystals and the structural damage of SF-FCNs by controlling the water. The work contributes to a theoretical framework for enhancing SF-FCNs quality through precise water and ice crystal control.

Quality analysis of dough and steamed bread under various freezing conditions

Freezing is a crucial step in the process of frozen foods. In this study, the effects of different freezing methods, including liquid nitrogen immersion freezing (LF), quick-freezing machine freezing (QF), packaging immersion freezing (PF), and ultralow temperature refrigerator freezing (UF), and freezing time (0, 15, 30, and 60 days) on the textural properties, dynamic rheological properties, water distribution, and structure of dough and the quality of end steamed bread were evaluated. Freezing resulted in a decline in the physicochemical properties of dough. UF- and QF-doughs had higher storage modulus and loss modulus, compared with PF- and LF-doughs. LF enhanced the textural attributes of the dough, resulting in reduced hardness and increased springiness. At 15 days of freezing, QF- and LF-doughs exhibited a compact and continuous structure with a smooth surface. Additionally, the correlation analysis elucidated that the weight loss rate and the bound water content of the dough had discernible impacts on the texture of both the dough and the resulting steamed bread. Overall, LF demonstrated a relatively high freezing efficiency and effectively maintained the quality of the dough for up to 15 days of freezing. These results offer valuable insights for the applications of freezing methods and time in frozen foods.

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.

Study on the Effect of Sorghum Flour Particle Size on the Storage Quality of Leavened Pancakes

Pancakes prepared with sorghum flour possess a high nutritional value, yet their quality is unstable and prone to degradation during storage. This instability can be attributed to the particle size of coarse cereal powder, which significantly influences the quality of flour products during storage. In this study, changes in the quality of these pancakes, prepared with varying particle sizes of sorghum flour, were meticulously analyzed during cold storage using advanced instruments such as a texture analyzer, nuclear magnetic resonance spectrometer, differential scanning calorimeter, X-ray diffractometer, and Fourier transform infrared spectrometer. Findings revealed that the hardness of leavened pancakes significantly increased over time. After a refrigeration period of 7 days, the hardness of wheat flour leavened pancakes increased by 56.60%. However, with a decrease in the particle size of sorghum flour, the increase in hardness diminished, thereby delaying the aging process of the pancakes. As the storage duration was extended, moisture migration within the pancakes occurred, and the sorghum flour pancakes with a smaller particle size exhibited a reduced moisture change rate, indicating an enhanced water holding capacity. In comparison to their wheat flour counterparts, sorghum flour leavened pancakes exhibited a substantial reduction in retrogradation enthalpy and crystallinity. The inclusion of sorghum flour effectively inhibited amylopectin recrystallization, thus slowing down the aging process of the pancakes. This inhibitory effect was more evident with decreasing sorghum flour particle sizes. Fourier transform infrared data indicated no significant alterations in absorption peaks across various wavelengths during cold storage. Although starch short-range orderliness increased with storage time, the use of sorghum flour with smaller particles reduced the degree of short-range orderliness in starch molecules throughout the cold storage period. Sorghum flour with a smaller particle size can inhibit water migration and amylopectin recrystallization, which subsequently delays pancake aging and enhances its quality stability during storage.

Effects of apple fiber on the physicochemical properties and baking quality of frozen dough during frozen storage

The effects of apple fiber on gluten structure and corresponding frozen dough quality during frozen storage were studied. The addition of 0.50% and 0.75% apple fiber effectively preserved gluten structure by inhibiting the breakage of disulfide bonds and promoting the formation of hydrogen bonds. Notably, the presence of 0.75% apple fiber increased the β-turn of gluten from 29.60% to 33.84%. Fiber-enriched frozen dough exhibited a smoother and more compact microstructure, but excessive fiber addition (more than 1.00%) had adverse effects. The freezable water content of frozen dough decreased as fiber addition increased. Correspondingly, the addition of 1.50% apple fiber resulted in a 56.08% increase in storage modulus, indicating improved viscoelasticity of the dough. Consequently, the addition of 0.50% and 0.75% apple fiber alleviated the quality deterioration of frozen dough bread in terms of larger specific volume, softer and more uniform crumb.

Comparison of pH-induced protein-polyphenol self-assembly methods: Binding mechanism, structure, and functional characteristics

Herein, we used pH-shifted and pH-driven methods to assemble kidney-bean protein isolate (KPI) and luteolin (Lut) into a nanocomplex and subsequently investigated their binding mechanism, structure, and functional properties. Results showed that the nanocomplex prepared by the pH-driven method exhibited a better encapsulation effect and controlled release of Lut. Fluorescence spectroscopy and molecular docking analysis showed that the binding affinities under alkaline conditions were higher than those under acidic and neutral conditions. Various spectral techniques were used to determine the structural changes in the KPI-Lut nanocomplex, including the transformation of α-helices and β-sheets and alteration of specific amino acid microenvironments, which were more pronounced in the pH-driven nanocomplex. The structural changes in the nanocomplex further affected their surface hydrophobicity and thermal stability. Additionally, the combination of KPI and Lut significantly improved the antioxidant activity and α-glucosidase inhibitory ability of the resultant nanocomplexes, particularly the one prepared by the pH-driven method.

Effects of natural products on functional constipation: analysis of active ingredient and mechanism

Constipation is a prevalent clinical ailment of the gastrointestinal system, yet its pathogenesis remains ambiguous. Despite the availability of numerous treatment modalities, they are insufficient in resolving the issue for patients. This work conducted a comprehensive review of the existing literature pertaining to the utilization of natural products for the treatment of constipation, with a focus on the efficacy of natural products in treating constipation, and to provide a comprehensive summary of their underlying mechanisms of action. Upon conducting a thorough review of the extant literature, we found that natural products can effectively treat constipation as modern synthetic drugs and compounded drugs with acetylcholinesterase (AChE) effects, rich in fiber and mucus, and the effects of increasing the tension of the ileum and gastrointestinal tract muscle, mediating signaling pathways, cytokine, excitability of the smooth muscle of the gastrointestinal tract, and regulating the homeostasis of intestinal flora. However, there is a wide variety of natural products, and there are still relatively few studies; the composition of natural products is complex, and the mechanism of action of natural products cannot be clarified. In the future, we need to further improve the detailed mechanism of natural products for the treatment of constipation.

Maternal supplementation with konjac glucomannan improves maternal microbiota for healthier offspring during lactation

BACKGROUND

The maternal diet during gestation and lactation affects the health of the offspring. Konjac glucomannan (KGM) is a significantly functional polysaccharide in food research, possessing both antioxidant and prebiotic properties. However, the mechanisms of how KGM regulates maternal nutrition remain insufficient and limited. This study aimed to investigate maternal supplementation with KGM during late gestation and lactation to benefit both maternal and offspring generations.

RESULTS

Our findings indicate that KGM improves serum low density lipoprotein cholesterol (LDL-C) and antioxidant capacity. Furthermore, the KGM group displayed a significant increase in the feed intake-related hormones neuropeptide tyrosine (NPY), Ghrelin, and adenosine monophosphate-activated kinase (AMPK) levels. KGM modified the relative abundance of Clostridium, Candidatus Saccharimonas, unclassified Firmicutes, and unclassified Christensenellaceae in sow feces. Acetate, valerate, and isobutyrate were also improved in the feces of sows in the KGM group. These are potential target bacterial genera that may modulate the host's health. Furthermore, Spearman's correlation analysis unveiled significant correlations between the altered bacteria genus and feed intake-related hormones. More importantly, KGM reduced interleukin-6 (IL-6) levels in milk, further improved IL-10 levels, and reduced zonulin levels in the serum of offspring.

CONCLUSION

In conclusion, maternal dietary supplementation with KGM during late gestation and lactation improves maternal nutritional status by modifying maternal microbial and increasing lactation feed intake, which benefits the anti-inflammatory capacity of the offspring serum. © 2024 Society of Chemical Industry.

Study on the interaction and gel properties of pork myofibrillar protein with konjac polysaccharides

BACKGROUND

Natural myofibrillar protein (MP) is sensitive to changes in the microenvironment, such as pH and ionic strength, and therefore can adversely affect the final quality of meat products. The aim of this study was to modify natural MP as well as to improve its functional properties. Therefore, the quality improvement effect of konjac polysaccharides with different concentrations (0, 1.5, 3, 4.5 and 6 g kg-1 protein) on MP gels was investigated.

RESULTS

With a concentration of konjac polysaccharides of 6 g kg-1 protein, the composite gel obtained exhibited a significant improvement of water binding (water holding capacity increased by 7.71%) and textural performance (strength increased from 29.12 to 37.55 N mm, an increase of 8.43 N mm). Meanwhile, konjac polysaccharides could help to form more disulfide bonds and non-disulfide covalent bonds, which enhanced the crosslinking of MP and maintained the MP gel network structure. Then, with the preservation of α-helix structure (a significant increase of 8.11%), slower protein aggregation and formation of small aggregates, this supported the formation of a fine and homogeneous network structure and allowed a reduction in water mobility.

CONCLUSION

During the heating process, konjac polysaccharides could absorb the surrounding water and fill the gel system, which resulted in an increase in the water content of the gel network and enhanced the gel-forming ability of the gel. Meanwhile, konjac polysaccharides might inhibit irregular aggregation of proteins and promote the formation of small aggregates, which in turn form a homogeneous and continuous gel matrix by orderly arrangement. © 2023 Society of Chemical Industry.

Tailoring microstructure and mechanical properties of pectin cryogels by modulate intensity of ionic interconnection

Porous morphology and mechanical properties determine the applications of cryogels. To understand the influence of the ionic network on the microstructure and mechanical properties of pectin cryogels, we prepared low-methoxyl pectin (LMP) cryogels with different Ca2+ concentrations (measured as R-value, ranging from 0 to 2) through freeze-drying (FD). Results showed that the R-values appeared to be crucial parameters that impact the pore morphology and mechanical characteristics of cryogels. It is achieved by altering the network stability and water state properties of the cryogel precursor. Cryogel precursors with a saturated R-value (R = 1) produced a low pore diameter (0.12 mm) microstructure, obtaining the highest crispness (15.00 ± 1.85) and hardness (maximum positive force and area measuring 2.36 ± 0.31 N and 12.30 ± 1.57 N·s respectively). Hardness showed a negative correlation with Ca2+ concentration when R ≤ 1 (-0.89), and a similar correlation with the porosity of the gel network when R ≥ 1 (-0.80). Given the impacts of crosslinking on the pore structure, it is confirmed that the pore diameter can be designed between 56.24 and 153.58 μm by controlling R-value in the range of 0-2.

Solid-state fermentation by S. cerevisiae with high resistance to ferulic acid improves the physicochemical properties of wheat bran and quality of bran-rich Chinese steamed bread

Wheat bran has numerous health benefits, but its poor processing and sensory properties limit its application in the staple food industry. Fermentation by S. cerevisiae changes the performance of wheat bran. However, high levels of ferulic acid (FA) inhibit S. cerevisiae. The effects of solid-state fermentation of S. cerevisiae with high resistance to FA on the physicochemical properties of wheat bran and the quality of bran-rich Chinese steamed bread (CSB) were investigated. The results showed that the growth of S. cerevisiae was inhibited by FA in a dose-dependent manner. Short-term adaptation strategies efficiently improved the tolerance of S. cerevisiae to FA stress. Compared with the parental strain (PS), fermentation of the short-term adapted strains (adapted strains) significantly increased the FA, total phenol, and soluble dietary fiber content in wheat bran. Wheat bran fermented by the adapted strains had a higher antioxidant capacity than wheat bran fermented by PS. In addition, compared with the PS, the wheat bran fermented by the adapted strains can decrease the hardness, improve the specific volume, and the quality of CSB. Thus, solid-state fermentation of the adapted strain is a potentially effective method to improve the nutritional and physicochemical properties of wheat bran as a cereal food ingredient.

Fine Tuning Water States in Hydrogels for High Voltage Aqueous Batteries

Hydrogels are widely used as quasi-solid-state electrolytes in aqueous batteries. However, they are not applicable in high-voltage batteries because the hydrogen evolution reaction cannot be effectively suppressed even when water is incorporated into the polymer network. Herein, by profoundly investigating the states of water molecules in hydrogels, we designed supramolecular hydrogel electrolytes featuring much more nonfreezable bound water and much less free water than that found in conventional hydrogels. Specifically, two strategies are developed to achieve this goal. One strategy is adopting monomers with a variety of hydrophilic groups to enhance the hydrophilicity of polymer chains. The other strategy is incorporating zwitterionic polymers or polymers with counterions as superhydrophilic units. In particular, the nonfreezable bound water content increased from 0.129 in the conventional hydrogel to >0.4 mg mg-1 in the fabricated hydrogels, while the free water content decreased from 1.232 to ∼0.15 mg mg-1. As a result, a wide electrochemical stability window of up to 3.25 V was obtained with the fabricated hydrogels with low concentrations of incorporated salts and enhanced hydrophilic groups or superhydrophilic groups. The ionic conductivities achieved with our developed hydrogel electrolytes were much higher than those in the conventional highly concentrated salt electrolytes, and their cost is also much lower. The designed supramolecular hydrogel electrolytes endowed an aqueous K-ion battery (AKIB) system with a high voltage plateau of 1.9 V and contributed to steady cycling of the AKIB for over 3000 cycles. The developed supramolecular hydrogel electrolytes are also applicable to other batteries, such as aqueous lithium-ion batteries, hybrid sodium-ion batteries, and multivalent-ion aqueous batteries, and can achieve high voltage output.

Alleviative effects of mannosylerythritol lipid-A on the deterioration of internal structure and quality in frozen dough and corresponding steamed bread

The effects of mannosylerythritol lipid-A (MEL-A) on the quality of frozen dough and corresponding steamed bread were investigated. The results revealed that the rheological properties of frozen dough were improved with the increment of MEL-A (0%-2.0%). Adding 1.5% and 2% MEL-A significantly reduced the moisture migration and enhanced the water-holding capacity of the frozen dough. Microstructure observation demonstrated that high levels of MEL-A enabled more starch granules to be embedded in the dough network. A series of product quality assessments illustrated that frozen dough steamed bread containing 2.0% of MEL-A had the largest specific volume (2.981 mL/g), the highest springiness (77.47%), more uniform and porous crumb structure. Moreover, MEL-A exhibited a positive effect on steamed bread's flavor profile, which was explored for the first time in this study. Hence, these results suggested that MEL-A has promising applications as a novel dough improver in the food industry.

Effect of a Bacterial Laccase on the Quality and Micro-Structure of Whole Wheat Bread

The gluten protein content in whole-wheat flour is low, which affects the elasticity and viscosity of the dough. Enzymatic modification of the protein may result in a network that mimics gluten, which plays an important role in the processing of whole-wheat foods. In this study, the effects of Halomonas alkaliantartica laccase (LacHa) on the quality parameters of whole-wheat bread were investigated. The optimum dosage of LacHa was 4 U/100 g of whole-wheat flour. At this dosage, whole-wheat bread exhibited the best specific volume and optimum texture parameters. Laccase also extended the storage duration of whole-wheat bread. We analyzed the micro-structure of the dough to determine its gluten-free protein extractable rate and free sulfhydryl group content, and verify that LacHa mediates cross-linking of gluten-free proteins. The results demonstrated that the cross-linking of gluten-free protein by LacHa improves the texture of whole-wheat bread. As a flour improver, LacHa has great developmental and application potential in baked-food production.

Inherent molecular characteristics and effect of garlic polysaccharides on dough micro- and mesoscopic properties

Directional control of the process of doughs with nutrition fortification is challenging. Thus, this study aimed to develop non-starch polysaccharides that can modify the quality of flour products. Polysaccharides were extracted from three different garlic cultivars, evaluated for physicochemical properties and used to enrich doughs for microstructure and mesoscopic characteristics analysis. We assessed the moisture distribution, texture characteristics, thermodynamic properties, dynamic viscoelastic properties, protein structure, microstructure and molecular interaction of the doughs and demonstrated a relatively high molecular weight, lower steric hindrance of molecular chains and higher cross-linking ability with the dough network in the supernatant polysaccharide from Yunnan single-clove-garlic (SGSOS) fraction. These features of SGSOS fraction improved the rheological, thermodynamic, texture characteristics, and water distribution of doughs. These findings provide information on the use of garlic polysaccharides during the processing and manufacturing of foods to enhance their processing adaptability and qualities.

Insight into curdlan alleviating quality deterioration of frozen dough during storage: Fermentation properties, water state and gluten structure

Curdlan was effective in alleviating quality deterioration of frozen dough during storage. This research explored the mechanisms from perspectives of fermentation properties, water state and gluten structure of frozen dough during storage, and the performance of corresponding steamed bread. Results showed that curdlan addition improved the gas-releasing capability and gas-holding capability of frozen dough, meanwhile enhanced the specific volume and textural properties of corresponding steamed bread. The melting enthalpy and NMR results demonstrated that curdlan restricted the conversation of bound water into freezable water, and inhibited the moisture migration in frozen dough. Frozen dough with 0.5% curdlan had significantly lower gluten macropolymers (GMP) depolymerization degree and free sulfhydryl (SH) content than the control, indicating that curdlan alleviated the depolymerization of GMP. Microstructure results proved that the deterioration of the structure was retarded by curdlan. This study contributes to understanding the theories for curdlan alleviating the deterioration of frozen dough during storage.

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.

Use of a compound modifier to retard the quality deterioration of frozen dough and its steamed bread

To retard the quality deterioration of the dough during frozen storage, the effects of a compound modifier (CM) comprised of sodium stearoyl lactate, VC, and β-glucanase on the properties of the frozen dough, as well as the quality of the frozen dough steamed bread were investigated. The results revealed that CM restricted the migration of water in the dough and improved its rheological properties. Furthermore, CM minimized the deterioration of specific volume and textural properties, and prevented starch retrogradation in the frozen dough steamed bread. Moreover, the addition of CM strengthened the secondary structure of gluten protein and formed a more resilient gluten network. The microstructure of the frozen dough steamed bread showed that CM reduced the damage caused by ice crystals on the gluten network. Overall, the use of CM strengthened the gluten network and effectively delayed the quality deterioration of the frozen dough, thus is potential as an improver for frozen dough.

Effect of Lactylated Gluten and Freeze-Thaw Cycles on Frozen Dough: From Water State and Microstructure

The influence of lactylated gluten and Freeze-Thaw Cycles on the water state, microstructure, and quality of frozen steamed bread dough was investigated. After three freeze-thaw cycles (3F/T), the specific volume of steamed bread with sodium lactate-treated gluten increased by 18.34% compared with the blank group and 5.73% compared with the wheat gluten (WG) group. Compared with wheat gluten, the texture properties of steamed bread with lactylated gluten increased significantly. Changes in rheological properties demonstrated that the frozen dough's viscoelasticity increased significantly. The lactylated gluten could reduce water mobility and decrease the content of freezable water in frozen dough. Moreover, the free sulfhydryl (SH) content increased, revealing that the protein was depolymerized. Based on the microstructure and corresponding protein network analysis (PNA), the total area and the number of protein network connection points of the dough adding lactylated gluten were significantly higher than those of the blank group and the WG group. In conclusion, lactylated gluten enhanced the freeze-thaw tolerance of frozen dough.

Application of Konjac Glucomannan with Chitosan Coating in Yellow Alkaline Noodles

To improve the quality of the characteristics of yellow alkaline noodles and enrich their nutritional value, konjac glucomannan (KGM) with or without chitosan coating were added to noodles, and their application effects were investigated in terms of color, texture, water absorption, starch digestion, total plate count (TPC) and microstructure. Chitosan-konjac glucomannan (CK) complex was firstly prepared by embedding konjac powder with chitosan sol. After embedding, the hydrophilicity of KGM decreased significantly. Then, either CK or native KGM were mixed evenly with flour before saline water, and soda was subsequently added to produce noodles. Compared with native KGM, CK provided the noodles with a higher brightness and a lighter yellow color. In terms of texture properties, although the firmness of CK noodles was weaker than that of KGM noodles, the tensile properties were enhanced. After embedding, the water absorption of CK noodles decreased and the content of resistant starch (RS) in the noodles increased. During storage, the TPC in CK noodles was significantly lower than that in KGM noodles. At a CK content of 5%, the noodles presented a lightness of 87.41, a b value of 17.75, a shear work of 39.9 g·cm, a tensile distance of 84.28 cm, a water absorption of 69.48%, a RS content of 17.97% and a TPC of 2.74 lg CFU/g at 10 days. In general, KGM with chitosan coating could improve the physicochemical qualities of noodles and extend their shelf life to a certain extent.

Classification, gelation mechanism and applications of polysaccharide-based hydrocolloids in pasta products: A review

Polysaccharide-based hydrocolloids (PBHs) are a group of water-soluble polysaccharides with high molecular weight hydrophilic long-chain molecules, which are widely employed in food industry as thickeners, emulsifiers, gelling agents, and stabilizers. Pasta products are considered to be an important source of nutrition for humans, and PBHs show great potential in improving their quality and nutritional value. The hydration of PBHs to form viscous solutions or sols under specific processing conditions is a prerequisite for improving the stability of food systems. In this review, PBHs are classified in a novel way according to food processing conditions, and their gelation mechanisms are summarized. The application of PBHs in pasta products prepared under different processing methods (baking, steaming/cooking, frying, freezing) are reviewed, and the potential mechanism of PBHs in regulating pasta products quality is revealed from the interaction between PBHs and the main components of pasta products (protein, starch, and water). Finally, the safety of PBHs is critically explored, along with future perspectives. This review provides a scientific foundation for the development and specific application of PBHs in pasta products, and provides theoretical support for improving pasta product quality.

Combined effect of konjac glucomannan addition and ultrasound treatment on the physical and physicochemical properties of frozen dough

The effects of dual sequential modification using konjac glucomannan and ultrasound treatments at power densities of 15-37.5 W/L on the hydration, rheology and structural characteristics of frozen dough were investigated in this study. The results revealed that the konjac glucomannan and ultrasound treatments improved the textural properties of frozen dough, but had a negative impact on its viscoelasticity. Furthermore, konjac glucomannan and ultrasound treatments increased the content of free sulfhydryl group and disulfide bond, as well as improved the freeze tolerance of dough. The results exhibited that the enthalpy of frozen dough decreased by 20.42 % compared with the frozen blank control dough under ultrasonic power density of 22.5 W/L. The network structure of frozen dough treated by konjac glucomannan and ultrasound was more ordered and integral than that of frozen blank control dough. These results provide valuable knowledge on the application of konjac glucomannan and ultrasound to frozen wheat-based foods.

Effect of sanxan gel on the quality of salt-free noodles during cooking

The effect and mechanism of sanxan on the quality of salt-free noodles (SFNs) were investigated from different cooking stages (initial stage, 1 min; optimum cooking time, OCT; overcooked time, OT). The results showed significant changes in the cooking process with the addition of 1.2% sanxan. The OCT for noodles with 1.2% sanxan (experimental group, EG) was extended from 5 to 7 min compared to the non-added noodles (blank group, BG) and 1.5% salt-containing noodles (control group, CG). The hardness and adhesiveness of BG, EG, and CG all decreased significantly during cooking. In contrast, the springiness, maximum tensile strength, and tensile fracture distance trended first to increase and then to decrease. At OCT, EG had the highest hardness (3971.69 ± 94.49 g), adhesiveness (372.26 ± 33.56 g s), and maximum tensile strength (41.51 ± 2.76 g), which remained large even after overcooking. However, those in BG and CG showed a significant reduction (p < 0.05). The proportion of free water increased progressively as cooking progressed, with CG showing the largest increase, from 82.29% to 91.19%, whereas EG showed the smallest increase, from 78.34% to 86.02%. During the cooking process, the addition of sanxan delayed the water migration, whereas salt promoted it. Sensory evaluation showed that EG was smoother in appearance than BG and tasted malty with a slight stickiness. Moreover, EG had the smallest k₁ and C_∞ values. Thus, sanxan is an effective additive to enhance the quality of SFNs and can replace the role of salt in noodles in some properties, which is beneficial for the development of SFNs.

The alleviative effect of curdlan on the quality deterioration of konjac glucomannan thermo-irreversible gels after commercial sterilization at 121 °C

This work employed different curdlan concentrations (0.00 %, 1.00 %, 1.50 %, 2.00 %, and 2.50 %) to alleviate the quality degradation of konjac glucomannan (KGM) gels after commercial sterilization at 121 °C for 15 min. The results showed that all levels of curdlan could retard the deterioration of KGM gels, with the best effect at 2.00 %. After commercial sterilization, incorporating curdlan into KGM gels greatly reduced the Tan σ (G"/ G'), total relaxation time and half-free water from 0.52, 89.85 ms and 98.26 % to 0.27, 38.48 ms and 21.42 %, respectively. Moreover, the addition of curdlan imparted a better texture to KGM gels, as reflected in the increase of hardness, springiness, water-holding capacity and whiteness value from 1400.85 g, 0.42, 87.92 % and 33.33 to 3461.68 g, 0.80, 96.50 % and 49.27, respectively. Furthermore, SEM images revealed that curdlan endowed KGM gels with a tighter structure and smaller pores, and the pore size distribution was reduced from 113.46 μm to17.91 μm, indicating a stronger interaction among molecules, as evidenced by XRD and FTIR results. KGM gels with curdlan possessed less proportion of complete crystallites and crystalline region. These findings suggested that curdlan can be the potently protectant for improving the quality of commercially sterilized KGM gel-based products.

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.

The properties of potato gluten-free doughs: comparative and combined effects of propylene glycol alginate and hydroxypropyl methyl cellulose or flaxseed gum

Different methods are often used to make gluten-free (GF) bread to get better bread characteristics. To explore the effects of emulsifiers and hydrocolloids on the characteristics of GF dough, different esterification levels of propylene glycol alginate (PGA), hydroxypropyl methyl cellulose (HPMC), flaxseed gum with (FG) different molecular weight, and the binary blends of HPMC/PGA and FG/PGA were added to GF dough, made with potato starch and potato protein in a ratio of 6:4. The results showed that the potato GF dough with FG and FG/PGA obtained a higher viscoelasticity than the other doughs. HPMC and FG promoted to the formation of network structure, but the network structure formed by PGA and their combination was more developed. It was found that all PGA, HPMC, FG and their combination could improve the softness of GF breads. The results provided a basis for optimizing the quality of potato GF bread.

Effect of Proofing on the Rheology and Moisture Distribution of Corn Starch-Hydroxypropylmethylcellulose Gluten-Free Dough

Dough rheology, mainly enabled by gluten in the traditional dough, determines the end-products' quality, particularly by affecting gas production and retention capacities during proofing. Gluten-free dough has quite different rheological performance compared with gluten-containing dough. To deepen the understanding of gluten-free dough, variations of rheology and moisture distribution of corn starch-hydroxypropylmethylcellulose (CS-HPMC) gluten-free dough in the process of proofing were studied. Significant differences were found in terms of soluble carbohydrate composition, moisture distribution, and rheology. Arabinose, glucose, fructose, and mannose were the main composition of soluble carbohydrates in CS-HPMC dough, out of which glucose was preferentially utilized during proofing. Non-freezable water content and third relaxation time decreased from 44.24% and 2171.12 ms to 41.39% and 766.4 ms, respectively, whereas the amplitudes of T₂₃ increased from 0.03% to 0.19%, indicating reduced bounded water proportion and improved water mobility with proofing time. Frequency dependence and the maximum creep compliance increased, whereas zero shear viscosity reduced, suggesting decreased molecular interactions and flowability, but improved dough rigidity. In conclusion, the reduced soluble carbohydrates and improved water mobility decreased molecular entanglements and hydrogen bonding. Furthermore, yeast growth restricted a large amount of water, resulting in declined flowability and increased rigidity.

Physicochemical and Structural Properties of Gluten-Konjac glucomannan Conjugates Prepared by Maillard Reaction

Gluten (Glu) is important to wheat products by forming a three-dimensional matrix. This study aimed to investigate the physicochemical and structural properties of gluten after conjugation with konjac glucomannan (KGM) through the Maillard reaction. The study revealed that the degree of graft increased with the prolonged reaction time. The Glu-KGM conjugates were possessed of increased β-sheet but decreased α-helix and β-turn, as well as unfolding and loose tertiary structures as the reaction proceeded. Among three different proportions, the Glu-KGM 1:1 conjugate was proved to have the most excellent foaming and emulsifying properties, and could form more rigid and firm gelation structures, which could be related to the decreased particle size and increased zeta potential of the conjugate. Overall, the physicochemical and structural properties of gluten were significantly related to the KGM ratios as well as the reaction period.

The Effect of Different Ratios of Starch and Freeze-Thaw Treatment on the Properties of Konjac Glucomannan Gels

The composite gels of konjac glucomannan (KGM) and corn starch (CS) were prepared and treated by the freeze-thaw method. For KGM-CS gels, as the starch ratio rose from 0 to 100%, storage modulus (G') decreased by 97.7% (from 3875.69 Pa to 87.72 Pa), degradation temperature decreased from 313.32 °C to 293.95 °C, and crystallinity decreased by 16.7%. For F-KGM-CS gels, G' decreased by 99.0% (from 20,568.10 Pa to 204.09 Pa), degradation temperature increased from 289.68 °C to 298.07 °C, and crystallinity decreased by 17.1% with more starch content. The peak in infrared spectroscopy shifted to a higher wavenumber with more starch and to a lower wavenumber by freezing the corresponding composite gels. The detected retrogradation of the composite gels appeared for KGM-CS with 80% starch and F-KGM-CS with 40% starch. The endothermic enthalpy of free water rose by 10.6% and 10.1% with the increase in starch for KGM-CS and F-KGM-CS, respectively. The results of moisture distribution found that bound water migrated to free water and the water-binding capacity reduced with more starch. The results demonstrated that the molecular interaction in composite gels was weakened by starch and strengthened by freezing.