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.

Improving the Edible and Nutritional Quality of Roasted Duck Breasts through Variable Pressure Salting: Implications for Protein Anabolism and Digestion in Rats

Variable pressure salting (VPS) is considered a novel salting approach to improve meat quality. This study aimed to investigate the effects of roasted duck's edible and nutritional quality after VPS through serum biochemical indicators and in vivo digestion properties in rats. The results show that roasted duck after VPS led to an increase in the total protein content (57.24 g/L) and blood glucose levels (6.87 mmol/L), as well as a decrease in the blood urea nitrogen content (11.81 mmol/L), in rats. Compared to rats fed base diets and roasted duck after static wet salting (SWS), those ingesting roasted duck after VPS exhibited higher values of apparent protein digestibility (51.24%), pepsin activity (2.40 U/mg), and trypsin activity (389.80 U/mg). Furthermore, VPS treatment improved the textural properties and microstructure of duck breasts shown by a higher immobilized water relaxation area and more ordered protein structures (α-helixes and β-sheets). These improvements enhanced the protein anabolism capacity and in vivo digestion properties in rats. Therefore, VPS represents a beneficial salting method for promoting effective digestion and absorption in rats.

Influence of roasted flaxseed marc flour on rheological, structural, fermentation, water distribution, and migration properties of wheat dough

Roasted flaxseed (RF) marc, which is a by-product obtained from RF oil extraction, has high nutritional value. This study evaluated the impact of RF marc flour on rheological, structural, fermentation, water distribution, and migration properties of the wheat dough. Results showed that adding RF into wheat flour (WF) could effectively increase the water absorption in the dough and retard the retrogradation of starch. The fermentation results revealed that adding RF could improve the gas retention coefficient of dough. Compared to the dough prepared with WF, the doughs enriched with RF had higher tan δ values (ratio of loss modulus G″ to storage modulus G'), indicating a more liquid-like property. The mobility of tightly bound and free water in dough was decreased by adding RF, whereas the distribution of free water was increased. On the one hand, adding RF would dilute the gluten content in dough, resulting in a weaker protein network. On the other hand, the dietary fiber and proteins in RF could offset the gluten dilution effect to some extent. Overall, the results suggested that the substitution level of RF in WF should be below 25% to avoid serious dough quality deterioration, and the RF-WF blended flour could be a potential ingredient to produce wheat products with moist taste. These findings could be useful for guiding the future usage of RF marc in wheat-based products.

Study on Self-Humidification in PEMFC with Crossed Flow Channels and an Ultra-Thin Membrane

In this study, a 3D model of a proton exchange membrane fuel cell (PEMFC) with crossed channels and an ultra-thin membrane is developed to investigate the feasibility of self-humidification; experiments utilizing a PEMFC stack with identical configurations are conducted to validate the simulation results and further investigate the effects of various operating conditions (OCs) on self-humidification. The results indicate that the crossed flow channel leads to enhanced uniformity of water distribution, resulting in improved cell performance under low/no humidification conditions. External humidifiers for the anode can be removed since the performance difference is negligible (≤3%) between RHa = 0% and 100%. Self-humidification can be achieved in the stack at 90 °C or below with an appropriate back pressure among 100-200 kPa. As the current density increases, there is a gradual convergence and crossing of the voltage at low RH with that at high RH, and the crossover points are observed at 60-80 °C with suitable pressure when successful self-humidification is achieved. Below the current density of the point, the stack's performance is inferior at lower RH due to membrane unsaturation, and conversely, the performance is inferior at higher RH due to flooding; this current density decreases with higher pressure and lower temperature.

Cryoprotective effect of soybean oil on surimi gels and the mechanism based on molecular dynamics simulation

The effect of soybean oil (SO) on freeze-thaw (F-T)-treated surimi was investigated and its related mechanism was revealed by molecular dynamics (MD) simulations. The results displayed that SO has a disrupting effect on the structure of fresh samples. However, in the F-T-treated samples, surimi gels supplemented with SO had a more uniform microstructure. Simultaneously, when SO was added from 0% to 7% in the F-T-treated samples, the gel strength increased from46.66 to 51.86 N · mm $$ 46.66\ \mathrm{to}\ 51.86\;\mathrm{N}\cdotp \mathrm{mm} $$ (p < .05), the physically bound water was increased from 92.90% to 94.15% (p < .05), and storage modulus was increased from 5939 to 6523 Pa. Triglycerides of SO generated hydrophobic interactions with myosin mainly in carbon chains. Computational results from MD simulations illustrated that the structure of myosin combined with triglycerides was more stable than that of myosin alone during temperature fluctuations (-20 to 4°C). During ice crystal growth, triglycerides absorbed on the myosin surface inhibited the growth of surrounding ice crystals and mitigated the ice crystal growth rate (from 7.54 to 5.99 cm/s). The addition of SO during the F-T treatments allowed myosin to be less negatively affected by ice crystal formation and temperature fluctuations and ultimately contributed to the formation of a more uniform network gel structure.

The Effect of Freeze-Thaw Cycles on the Microscopic Properties of Dumpling Wrappers

Dumplings are a traditional Chinese food welcomed by Chinese people. Research has indicated that process of quick-frozen wheat cultivars and their gliadins are all related to the quality and shelf-life of dumplings. Therefore, the effect of freeze-thaw cycles on the textural properties and microscopic characteristics of two types of quick-frozen dumpling wrappers (Zhaomai and Wenmai 19) and conformation of their gliadins were investigated. Scanning electron microscopy showed that Wenmai 19 dumpling wrappers had apparent damage after the first cycle, but Zhaomai wrappers did not reveal significant changes until the fourth cycle. The particle size distribution in the starch granules of Wenmai 19 wrappers varied in terms of mechanical damage, but Zhaomai delayed or avoided such effects. FT-IR found a loose protein structure of the gliadins. Differential scanning calorimetry showed that gliadins of Wenmai 19 degenerated more than those of Zhaomai. The crosslinking of gliadin and glutenin maintained a high-quality gluten network, thus protecting the gliadin stability from ice crystals. In turn, the gliadin maintained the strength of the gluten network. Therefore, raw flours with high-quality protein networks are more suitable for frozen dumplings. Freeze-thaw cycles dramatically decreased the textural characteristics of dumpling wrappers and the microscopic characteristics of their gliadin proteins. Concerning wheat cultivars with weak gluten, flours with high-quality protein networks are more suitable as raw materials for frozen dumplings.

Effect of Artemisia sphaerocephala krasch gum on the functional properties of pork batters

The influence of the incorporation of Artemisia sphaerocephala krasch gum (ASK gum; 0-0.18%) on the water holding capability (WHC), texture, color, rheological property, water distribution, protein conformation and microstructure of pork batters was investigated. The results showed that the cooking yield, WHC and L* value of pork batter gels significantly increased (p < .05) with the increasing incorporation of ASK gum, and the highest value were observed at 0.15%; the a* value decreased significantly (p < .05) and no significance was obtained in b* value (p > .05); the hardness, elasticity, cohesiveness and chewiness increased first and then decreased, and reached the highest value at 0.15%. The rheological results showed that the higher G' value was obtained in pork batters by the incorporation of ASK gum; the low field NMR analysis indicated that ASK gum significantly increased the proportion of P2b and P21 (p < .05) and decreased the proportion of P22 ; Fourier transform infrared spectroscopy (FTIR) indicated that the ASK gum significantly reduced the α-helix content and increased the β-sheet content (p < .05). Scanning electron microscopy results suggested that the incorporation of ASK gum could promote the formation of a more homogeneous and stable microstructure of pork batter gels. Therefore, appropriate incorporation (0.15%) of ASK gum may improve the gel properties of pork batters, and while excessive incorporation (0.18%) could weaken the gel properties.

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.

Effect of Tea Polyphenols on the Storage Stability of Non-Fermented Frozen Dough: Protein Structures and State of Water

The usage of tea polyphenols (TPs) as a natural food additive into non-fermented frozen dough (NFFD) has rarely been investigated, and results have been controversial. Hence, this study investigated the effect of TPs at various levels (0, 0.5, 1, and 2%) on the quality of NFFD stored from 0 to 4 weeks. The rheological characteristics, water state, protein, and its microstructure were analyzed by DSC, LF-NMR, SDS-PAGE, FT-IR, and SEM, respectively. Results showed that the 0.5% TP group delayed the deterioration of protein and inhibited the water migration in dough throughout the whole frozen storage period. In addition, the 0.5% TP group enhanced the rheological properties of NFFD and stabilized the sulfhydryl content and the secondary structure in the gluten network. On the contrary, opposite phenomena were found in the 1 and 2% TP groups, which might be due to the induction of excess hydroxyl groups from TPs. In conclusion, our results suggested that a proper addition of TPs, but not an excessive amount (>1%), exhibited beneficial effects in maintaining the quality of NFFD during the 4-week frozen storage. Moreover, this paper elucidated the mechanism of TPs in influencing the protein structure and water state of NFFD during storage and provided new insight into its application in dough-based foods.

Effect of Frozen Treatment on the Sensory and Functional Quality of Extruded Fresh Noodles Made from Whole Tartary Buckwheat

Extruded noodles made from whole Tartary buckwheat are widely known as healthy staple foods, while the treatment of fresh noodles after extrusion is crucial. The difference in sensory and functional quality between frozen noodles (FTBN) and hot air-dried noodles (DTBN) was investigated in this study. The results showed a shorter optimum cooking time (FTBN of 7 min vs. DTBN of 17 min), higher hardness (8656.99 g vs. 5502.98 g), and less cooking loss (5.85% vs. 21.88%) of noodles treated by freezing rather than hot air drying, which corresponded to better sensory quality (an overall acceptance of 7.90 points vs. 5.20 points). These effects on FTBN were attributed to its higher ratio of bound water than DTBN based on the Low-Field Nuclear Magnetic Resonance results and more pores of internal structure in noodles based on the Scanning Electron Microscopy results. The uniform water distribution in FTBN promoted a higher recrystallization (relative crystallinity of FTBN 26.47% vs. DTBN 16.48%) and retrogradation (degree of retrogradation of FTBN 34.67% vs. DTBN 26.98%) of starch than DTBN, strengthening the stability of starch gel after noodle extrusion. FTBN also avoided the loss of flavonoids and retained better antioxidant capacity than DTBN. Therefore, frozen treatment is feasible to maintain the same quality as freshly extruded noodles made from whole Tartary buckwheat. It displays significant commercial potential for gluten-free noodle production to maximize the health benefit of the whole grain, as well as economic benefits since it also meets the sensory quality requirements of consumers.

Analysis of Water Distribution and Muscle Quality of Silver Carp (Hypophthalmichthys molitrix) Chunks Based on Electron-Beam Irradiation

Electron-beam irradiation (EBI) is an efficient, safe, and nonthermal sterilization technique that is extensively used in food preservation research. Here we report the effects of different EBI doses (0, 4, 8 kGy) and preservation temperatures (room temperature [RT], 4 °C) on the muscle water distribution and muscle quality indices of silver carp chunks (SCCs). The highest entrapped water content was found in the 4-kGy-irradiated/4-°C-stored samples. The expressible moisture content (EMC) of the SCCs increased with increasing irradiation dose and was significantly lower in the RT group than in the 4 °C group. The irradiation dose and preservation temperature had no significant effect on the moisture content, whiteness value and protein content of SCCs (p > 0.05). When the irradiation dose reached 8 kGy, AV value, POV value and TVB value were significantly increased (p < 0.05). The myofibrillar protein content and actomyosin content of the SCCs in the 4 °C group was higher than that of the specimens in the RT group by 0.29−0.98 mg/mL (p < 0.05) and 36.21−296.58 μg/mL (p < 0.05), respectively. Overall, EBI treatment (4 kGy) and low-temperature preservation (4 °C) helped retain the muscle water content of the SCCs and preserve their quality, thereby endorsing the EBI treatment of silver carp products.

Clean and Safe Drinking Water Systems via Metagenomics Data and Artificial Intelligence: State-of-the-Art and Future Perspective

The use of next-generation sequencing technologies in drinking water distribution systems (DWDS) has shed insight into the microbial communities' composition, and interaction in the drinking water microbiome. For the past two decades, various studies have been conducted in which metagenomics data have been collected over extended periods and analyzed spatially and temporally to understand the dynamics of microbial communities in DWDS. In this literature review, we outline the findings which were reported in the literature on what kind of occupancy-abundance patterns are exhibited in the drinking water microbiome, how the drinking water microbiome dynamically evolves spatially and temporally in the distribution networks, how different microbial communities co-exist, and what kind of clusters exist in the drinking water ecosystem. While data analysis in the current literature concerns mainly with confirmatory and exploratory questions pertaining to the use of metagenomics data for the analysis of DWDS microbiome, we present also future perspectives and the potential role of artificial intelligence (AI) and mechanistic models to address the predictive and mechanistic questions. The integration of meta-omics, AI, and mechanistic models transcends metagenomics into functional metagenomics, enabling deterministic understanding and control of DWDS for clean and safe drinking water systems of the future.

Influence of the Addition of Extruded Endogenous Tartary Buckwheat Starch on Processing and Quality of Gluten-Free Noodles

Extruded starch could be used as a thickener for food processing due to its pre-gel properties. This study aimed to explore the influence of the addition of extruded endogenous Tartary buckwheat starch (ES) on the process and quality of gluten-free noodles. ES was mixed with Tartary buckwheat flour in different proportions (10–40%) to prepare the blended flour and noodles. When the content of ES was increased, the swelling power of blended flour at 90 °C had no significant changes, and the decrease in peak viscosity of blended flour was reduced. This indicated that the high-content ES could afford better thermal stability for blended flour and inhibit the swelling ability. The higher level of ES was beneficial to the formation and stabilization of dough, and the improvement of noodle tensile strength. Furthermore, there was no difference in cooking loss between noodles with 30% and 40% ES addition. The microstructure and water distribution of the noodles prepared by blended flour indicated that the gel-entrapped structure organized by the higher content ES could be closely related to the above results. In conclusion, higher ES could contribute to improving the processing properties and quality of noodles.

Impact of Maltitol and Sorbitol on Technological and Sensory Attributes of Biscuits

Overconsumption of sugars in diets is associated with many health problems, including dental diseases, diabetes and obesity. However, removing sugar from products such as biscuits is still a challenge for manufacturers and has been limited in Europe since the evolution of the EU regulation in January 2018, allowing only polyols and non-sweetening bulking agents as sugar substitutes. This study investigated the effects of fully replacing sugar with two polyols, maltitol and sorbitol, in short-dough biscuits. Morphological, textural and visual characteristics were studied as well as sensory properties. The reformulated biscuits were more compact in shape and structure. They were also less prone to checking, which was attributed to a more homogeneous water distribution at the end of baking, especially with sorbitol. Polyol biscuits were surprisingly colourful, especially sorbitol ones, although polyols are not normally involved in Maillard reactions. Sensory tests, however, showed a depreciation of the products compared to the control. Sorbitol biscuits were the least preferred but maltitol ones were quite well accepted compared to the control. Thus, maltitol is an excellent potential substitute for this type of product.

Investigation on the correlation between changes in water and texture properties during the processing of surimi from golden pompano (Trachinotus ovatus)

Water and texture properties are important indicators for evaluating surimi and surimi seafood quality. The present study assessed the impact of surimi processing on the water and texture properties and analyzed their correlations. The results showed that the moisture content exhibited significant positive correlations with T₂₂ and A₂₂ (P < 0.05). However, water-holding capacity (WHC) revealed significant negative correlation with T₂₁ and A₂₂ (P < 0.05). Moreover, correlations between water and texture properties were observed. Moisture content and A₂₂ displayed significant negative correlation with hardness (P < 0.05). WHC exhibited significant positive correlations with cohesiveness, springiness, and chewiness (P < 0.05), whereas T₂₁ exhibited significant negative correlation with those properties (P < 0.05). Springiness is an important indicator for texture properties of surimi gel. T₂₁ and WHC exhibited significant correlations with springiness (P < 0.05). We used two equations to assess the relationship between springiness and T₂₁ (y = 9.64 × x² - 33.79 × x + 29.62, R² = 0.995, P < 0.05) and between springiness and WHC (y = 0.57 + 9.05/{1+e^{[-29.29 × ( x - 83.90)]} }^0.01 , R² = 0.999, P < 0.05), respectively. Verification experiments proved that these two regression equations could be used to predict the change law among feature indicators during the processing of surimi seafood. The present study finds an easy-to-control method to monitor the quality of surimi production and processing for all the stages, and provides ideas for quality design of surimi products. PRACTICAL APPLICATION: The quality of surimi seafood is affected by the process used for surimi production. Early detection of the material quality can efficiently prevent resource wastage. The feature indicators and their correlations help in easy-to-control of all surimi processing stages. Low-field nuclear magnetic resonance (LF-NMR) is a fast, nondestructive method for monitoring food real-time, but the instrument is expensive; whereas water-holding capacity and texture profile analysis (TPA) are traditional methods but time-consuming and material-consuming. Surimi enterprises or researchers choose the right methods based on their needs.

Effect of Multiple Freeze-Thaw Cycles on Myoglobin and Lipid Oxidations of Grass Carp (Ctenopharyngodon idella) Surimi with Different Pork Back Fat Content

Fresh grass carp was used to produce surimi and 50 g/kg, 100 g/kg, or 150 g/kg pork back fat was added. The water distribution, thiobarbituric acid reactive substances (TBARS), myoglobin oxidation, color parameter (L*, a*, and b*), heme and non-heme iron content of samples were determined to analyze the effects of different fat content on the oxidation of myoglobin and lipids during multiple freeze-thaw cycles of grass carp surimi. Both multiple freeze-thaw cycles and increased fat content lead to an increase in TBARS, a blue shift in the absorption peak of myoglobin porphyrin, a decrease in heme iron content, and an increase of non-heme iron content. Repeated freeze-thaw caused a decrease in immobilised water content and L*, and caused an increase in a* and b*. Increased fat content caused an increase in immobilised water content, L* and a*, and caused a decrease in b*.

Effect of laver powder on textual, rheological properties and water distribution of squid (Dosidicus gigas) surimi gel

In order to ameliorate the gel quality of Dosidicus gigas surimi, the effects of laver powder on gel properties, rheological properties, and water-holding capacity (WHC) were investigated. Results indicated that the addition of laver powder could significantly increase the hardness, chewiness, and breaking force of surimi gels. However, the texture indexes and gel strength began to decline when additional amount exceeded 0.6%. Rheological results demonstrated that the addition of laver powder increased the storage modulus (G') and viscosity of surimi, prolonged protein denaturation temperature in surimi gels. Moreover, the WHC of surimi gel was improved with the increase of laver powder. Further analyses in low-field nuclear magnetic resonance revealed that laver powder could shorten the transverse relaxation time, enhanced the combination with water, and altered the distribution of different water categories. The proportion of bound water and immobilized water reached its maximum and minimum at 0.6% of laver powder, respectively. Correlation analyses showed that WHC of surimi gel was negatively correlated well with the proportion of loose-bound water, but positively correlated with the strong-bound water and free water. In conclusion, the results supported that 0.6% was the optimal additional amount of laver powder for the squid-based surimi production based on the current ingredients of surimi products.

Effects of sourdough on improving the textural characteristics of microwave-steamed cake: A perspective from dielectric properties and water distribution

A sourdough combined with microwave heating method was adopted to make steamed cake (SSC), the dough yield, fermentation time and additive amount of sourdough were optimized by Response Surface Methodology (RSM) to obtain microwave-steamed cake (MSSC) with high-quality attributes and then the potential mechanism of sourdough on the improvement of the MSSC texture was investigated. The addition of sourdough with the optimized parameters could greatly improve the specific volume, porosity, hardness, and chewiness of MSSC, which was mainly related to changes in dielectric properties and water distribution. The results of dielectric properties confirmed that sourdough increased the dielectric properties of the system during microwave heating, affecting the microwave heating characteristics. And the changes of water states and distribution by T₂ relaxation analysis showed that sourdough restricted water mobility during heating and facilitated the retention of water trapped in MSSC. Additionally, the scanning electron microscopy (SEM) images indicated that sourdough weakened the gluten network structure, and triggered a looser and smoother microstructure. PRACTICAL APPLICATION: Steamed cake (SSC) is one of the most popular fermented foods in China, while its commercial development is greatly limited by the drawbacks of traditional steam heating. In recent years, the applications of microwave heating and sourdough in cereal-based foods processing have gained more and more interest. However, there is little information about the application of sourdough combined with microwave heating in SSC production. This study revealed that sourdough addition increased the specific volume, porosity, texture, and consumer preference of MSSC, providing a natural, high-efficiency, and easy-to-operate means for the fabrication of high-quality fermented foods.

Spring Leafing Phenology Favors Younger Culms of Moso Bamboo: Aspects From Water Use Relations

As the most widely distributed giant running bamboo species in China, Moso bamboo (Phyllostachys edulis) can accomplish both development of newly sprouted culms and leaf renewal of odd-year-old culms within a few months in spring. The two phenological events in spring may together change water distribution among culms in different age categories within a stand, which may differ from our conventional understanding of the negative age effect on bamboo water use. Therefore, to explore the effect of spring shooting and leaf phenology on age-specific water use of Moso bamboo and potential water redistribution, we monitored water use of four culm age categories (newly sprouted, 1-, 2-, and 3-year-old; namely A0, A1, A2, A3) in spring from March to June 2018. For newly sprouting culms, the spring phenological period was classified into five stages (incubation, culm-elongation, branch-development, leafing, established). Over these phenological stages, age-specific accumulated sap flux density showed different patterns. The oldest culms, A3, were not influenced by leaf renewal and kept nearly constant and less water use than the other aged culms. However, A2, which did not renew their leaves, had the most water use at the two initial stages (incubation, culm-elongation) but consumed less water than A0 and A1 after the fourth stage (leafing). At the end of June, water use of the four age categories sorted in order of A0 > A1 > A2 > A3, which confirms the conventional thought and observations, i.e., a negative age effect. The results indicate that new leaf flushing may benefit younger culms (A1 and A0) more than older culms (A2 and A3), i.e., increasing their transpiration response to radiation and share of the stand transpiration. With the underground connected rhizome system, the bamboo stand as an integration seems to balance its water use among culms of different ages to support the water use of freshly sprouted culms during their developing period.

Effect of the moisture equilibrium process on the expansion behavior of instant controlled pressure drop (DIC) drying of dried apple cubes

BACKGROUND

Recently, consumers' demand on high quality dried fruit or vegetable products have increased dramatically. The instant controlled pressure drop (DIC) dried products have attracted consumers' attention due to its unique sensory characteristics. The product quality, especially the appearance quality of the DIC products, is influenced closely by water status and water distribution in the material, which is rarely reported in the literatures. In this study, a comparison system for the apple cubes with or without the moisture equilibrium process (MEP) was established to explain the effect of the MEP on the expansion behavior of the DIC dried apple cube.

RESULTS

The results showed that the MEP could induce a more homogenous spatial distribution of water in the semi-dried apple cube after pre-drying. Meanwhile, the MEP treated and DIC dried apple cubes showed better quality in terms of the appearance and texture properties including high porosity (71.77%), large pores (maximum pore size of 1.55 mm), and thin pore walls (pore wall thickness of 0.079 mm).

CONCLUSION

The MEP was approved to be a compulsory treatment to achieve the DIC dried apple cubes with good expansion behavior. © 2019 Society of Chemical Industry.

Different Post-Sowing Nitrogen Management Approaches Required to Improve Nitrogen and Water Use Efficiency of Canola and Mustard

Strategic use of nitrogen (N) may improve N use efficiency, but there is limited information on the influence of N supply at crucial growth stages on N accumulation, water use, and water use efficiency of canola and mustard. In this study, we hypothesize that genetic variation among canola and mustard can alter the response of timing and rate of post-sowing N application at targeted phenological growth stages by improving N and water use and their efficiencies. Field experiments were conducted in South Australia during two growing seasons with contrasting water availabilities. Two mustard and four canola cultivars, including two triazine tolerant (TT) and two non-TT cultivars were evaluated under different post-sowing N application strategies comprising three N rates and different timings of application. Mustard used more water than canola in the season with higher rainfall, but canola and mustard used similar amounts of water in the drier season. Nitrogen increased the water use efficiency (WUE) of canola and mustard cultivars. Nitrogen rate and timing did not influence the total water use of canola and mustard but influenced the partitioning of pre- and post-flowering water use. Even though, highest N uptake was observed in the treatment with continuous supply of N with 200 kg N ha^-1 in five splits it did not influence the N efficiencies parameters which indicate that yield of canola and mustard are limited by N rate in these environments. In treatment with limited N supply, targeting N at the rosette stage improve N use efficiency of canola and mustard. However, the limited N uptake potential of mustard makes timing of N application the most important consideration whereas correct N rate should be main consideration for canola.

Modeling chloramine decay in full-scale drinking water supply systems

Chloramines are commonly used as secondary disinfectants in drinking water treatment, providing a residual for disinfection as drinking water moves to consumers. Chloramines are inherently unstable, undergoing autodecomposition reactions even in the absence of reactive substances. In the presence of natural organic matter (NOM), chloramine loss accelerates due to additional reaction pathways. In this study, batch reaction models for chloramine loss due to autodecomposition and the presence of NOM were developed. A case study was carried out for the Town of Cary, North Carolina. A hydraulic model of Cary's distribution system was developed and calibrated using the EPANET toolkit with operational and water demand data supplied by Cary. Then, water age from the hydraulic model was used together with the batch model of chloramine decay to successfully predict chloramine concentrations spatially and temporally throughout the network. The capabilities of the EPANET-MSX toolkit to model chloramine loss in a distribution network are explored. PRACTITIONER POINTS: A batch reaction model of chloramine decay over time due to autodecomposition reactions and additional reactions with NOM was developed and validated. A hydraulic model of the Town of Cary's water distribution network was developed and calibrated using operational and water demand data. Water age reported by the calibrated hydraulic model was used in conjunction with the batch reaction model of chloramine decay to successfully predict chloramine concentrations spatially and temporally throughout the network.

Effects of T-2 toxin on histopathology, fatty acid and water distribution of shrimp (Litopenaeus vannamei) muscle

T-2 toxin (T-2), one of the naturally occurring mycotoxins, often accumulates in aquatic animals from contaminated feed. Shrimp (n = 30 per group) were fed with different concentrations (0, 0.5, 1.5, 4.5 and 13.5 mg kg^-1) of T-2 for 20 days. Changes in histopathology, fatty acid and water distribution of shrimp muscle were analyzed. Histopathology of shrimp muscle showed dose-dependent marked degenerative and necrotic changes on exposure to dietary T-2. The T-2 significantly (P < 0.05) affected the muscle fatty acid composition. ∑SFA, ∑MUFA and ∑PUFA initially decreased and then increased slowly in the high-dosed groups. C16:0, C18:1n-9 and C18:2n-6 were the main saturated fatty acid (SFA), monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA), respectively. Also, T-2 significantly affected water distribution in shrimp muscle. High doses of T-2 reduced free water content, resulting in a reduction in the water holding capacity and hence changes to the shrimp muscle quality. Collectively, these results illustrated that T-2 significantly affects the fatty acid and water distribution, and also muscle histopathology, all of which would result in a reduction in the quality and nutritional value of shrimp.

Setting Characteristics, Mechanical Properties and Microstructure of Cement Pastes Containing Accelerators Mixed with Superabsorbent Polymers (SAPs): An NMR Study Combined with Additional Methods

In this study, the setting property and mechanical strength of cement pastes containing accelerators (CPCA) with or without superabsorbent polymers (SAPs) were first studied. The early microstructure evolution and water distribution at 7 and 28 days were probed by 1D (T₂) and 2D (T₁-T₂ maps) H¹ nuclear magnetic resonance (NMR) relaxometry, and the microstructure was systematically investigated by using mercury intrusion porosimetry (MIP), back-scattered electron (BSE) image and energy-dispersive X-ray spectroscopy (EDX) analysis. Results showed that the SAPs in the cement paste containing accelerators had various influences on setting time and compressive strength depending on the type of accelerators. The presence of SAPs in the cement paste containing alkaline free accelerators could alleviate the decrease of internal relative humidity, promote hydration and help to modify the pore structure. Moreover, it was observed that the SAP cavities could be nicely filled with calcium hydroxide (CH) in the cement paste with alkaline free accelerators.

In Operando Quantification of Three-Dimensional Water Distribution in Nanoporous Carbon-Based Layers in Polymer Electrolyte Membrane Fuel Cells

Understanding the function of nanoporous materials employed in polymer electrolyte membrane fuel cells (PEMFCs) is crucial to improve their performance, durability, and cost efficiency. Up to now, the water distribution in the nm-sized pore structures was hardly accessible during operation of the cells. Here we demonstrate that phase contrast synchrotron X-ray tomography allows for an in operando quantification of the three-dimensional water distribution within the nm-sized pores of carbon-based microporous layers (MPLs). For this purpose, a fuel cell design optimized for tomographic phase contrast measurements was realized. Water in the pores of the entire MPL was detected and quantified. We found an inhomogeneous distribution of the local water saturation and a sharp boundary between mostly filled MPL and almost empty areas. We attribute the latter observation to the two-phase boundary created because condensation takes place predominantly on one side of the boundary. Furthermore, high water saturation in large areas hints at gas diffusion or transport along preferred three-dimensional paths through the material, therefore bypassing most of the MPL volume. Our approach may contribute significantly to future investigations of nanoporous fuel cell materials under realistic operating conditions.

Application of near infrared reflectance (NIR) spectroscopy to identify potential PSE meat

BACKGROUND

Pale, soft and exudative (PSE) meat is a quality problem that causes a large economic loss to the pork industry. In the present work, near infrared (NIR) quantification and identification methods were used to investigate the feasibility of differentiating potential PSE meat from normal meat.

RESULTS

NIR quantification models were developed to estimate meat pH and colour attributes (L*, a*, b*). Promising results were reported for prediction of muscle pH (R(2) CV  = 70.10%, RPDCV = 1.83) and L* (R(2) CV  = 77.18%, RPDCV = 1.91), but it is still hard to promote to practical application at this level. The Factorisation Method applied to NIR spectra could differentiate potential PSE meat from normal meat at 3 h post-mortem. Correlation analysis showed significant relationship between NIR data and LF-NMR T2 components that were indicative of water distribution and mobility in muscle. PSE meat had unconventionally faster energy metabolism than normal meat, which caused greater water mobility.

CONCLUSION

NIR spectra coupled with the Factorisation Method could be a promising technology to identify potential PSE meat. The difference in the intensity of H2 O absorbance peaks between PSE and normal meat might be the basis of this identification method. © 2015 Society of Chemical Industry.

Probing the Distribution of Water in a Multi-Component System by Solid-State NMR Spectroscopy

PURPOSE

To characterize the distribution of water among various components in a powder blend using solid-state NMR spectroscopy.

METHODS

Water sorption behavior of theophylline anhydrate and excipients was determined by dynamic vapor sorption (DVS) and Karl Fischer Titration (KFT) after storing them in humidity chambers for 1 week at room temperature (RT) and calibration curves were generated for water content vs. (1)H T 1 relaxation times. Powder blends (either with microcrystalline cellulose or lactose as diluent) were stored at different relative humidity (RH) conditions and analyzed periodically using solid-state NMR, powder X-ray diffraction, and KFT.

RESULTS

Anhydrous theophylline converted to the hydrate at ≥ 84% RH. Based on the calibration curves of water content vs. relaxation times, the distribution of water in the powder blends was estimated. The total water content calculated using ssNMR was in good agreement with values measured using KFT. In blends stored at 90% RH, theophylline anhydrate-to-hydrate conversion did not occur in 1 week.

CONCLUSIONS

The distribution of water in multi-component powder blends was successfully determined using correlation between (1)H T 1 relaxation times and total water content. Excipient water sorption inhibited hydrate formation in theophylline at 90% RH. Water distribution was affected by excipient type. The extent of water sorbed by excipients in blends was found to be different than their standalone equilibrium water content.

Water Dynamics in Egg White Peptide, Asp-His-Thr-Lys-Glu, Powder Monitored by Dynamic Vapor Sorption and LF-NMR

Water absorbed into the bulk amorphous structure of peptides can have profound effects on their properties. Here, we elucidated water dynamics in Asp-His-Thr-Lys-Glu (DHTKE), an antioxidant peptide derived from egg white ovalbumin, using water dynamic vapor sorption (DVS) and low-field nuclear magnetic resonance (LF-NMR). The DVS results indicated that parallel exponential kinetics model fitted well to the data of sorption kinetics behavior of DHTKE. Four different proton fractions with different mobilities were identified based on the degree of interaction between peptide and water. The water could significantly change the proton distribution and structure of the sample. The different phases of moisture absorption were reflected in the T2 parameters. In addition, the combined water content was dominant in the hygroscopicity of DHTKE. This study provides an effective real-time monitoring method for water mobility and distribution in synthetic peptides, and this method may have applications in promoting peptide quality assurance.

Time-Domain Nuclear Magnetic Resonance Investigation of Water Dynamics in Different Ginger Cultivars

Different ginger cultivars may contain different nutritional and medicinal values. In this study, a time-domain nuclear magnetic resonance method was employed to study water dynamics in different ginger cultivars. Significant differences in transverse relaxation time T2 values assigned to the distribution of water in different parts of the plant were observed between Henan ginger and four other ginger cultivars. Ion concentration and metabolic analysis showed similar differences in Mn ion concentrations and organic solutes among the different ginger cultivars, respectively. On the basis of Pearson's correlation analysis, many organic solutes and 6-gingerol, the main active substance of ginger, exhibited significant correlations with water distribution as determined by NMR T2 relaxation, suggesting that the organic solute differences may impact water distribution. Our work demonstrates that low-field NMR relaxometry provides useful information about water dynamics in different ginger cultivars as affected by the presence of different organic solutes.

Characterization of Oat (Avena nuda L.) β-Glucan Cryogelation Process by Low-Field NMR

Low-field nuclear magnetic resonance (LF-NMR) is a useful method in studying the water distribution and mobility in heterogeneous systems. This technique was used to characterize water in an oat β-glucan aqueous system during cryogelation by repeated freeze-thaw treatments. The results indicated that microphase separation occurred during cryogelation, and three water components were determined in the cryostructure. The spin-spin relaxation time was analyzed on the basis of chemical exchange and diffusion exchange theory. The location of each water component was identified in the porous microstructure of the cryogel. The pore size measured from the SEM image is in accordance with that estimated from relaxation time. The formation of cryogel is confirmed by rheological method. The results suggested that the cryogelation process of the polysaccharide could be monitored by LF-NMR through the evolution of spin-spin relaxation characteristics.

Study of water dynamics in the soaking, steaming, and solid-state fermentation of glutinous rice by LF-NMR: a novel monitoring approach

Solid-state fermentation (SSF) of starchy grain is a traditional technique for food and alcoholic beverage production in East Asia. In the present study, low-field nuclear magnetic resonance (LF-NMR) was introduced for the elucidation of water dynamics and microstructure alternations during the soaking, steaming, and SSF of glutinous rice as a rapid real-time monitoring method. Three different proton fractions with different mobilities were identified based on the degree of interaction between biopolymers and water. Soaking and steaming significantly changed the proton distribution of the sample. The different phases of SSF were reflected by the T2 parameters. In addition, the variations in the T2 parameters were explained by the microstructure changes of rice induced by SSF. The fermentation time and T2 parameters were sigmoidally correlated. Thus, LF-NMR may be an effective real-time monitoring method for SSF in starch systems.

Proteolysis process in fermented sausage model systems as studied by NMR relaxometry

Proton NMR relaxation analyses were performed in sausage model systems (SMS) at different manufacturing times (0, 1, 3, 5, 7, and 9 days) to evaluate changes in water distribution and mobility. Three different water populations were identified, T2b (5-10 ms), T21 (30-70 ms), and T22 (100-300 ms), and the progress of ripening could be followed as a shift toward shorter relaxation times. In addition, the combined effect of adding commercial proteases (Pronase E and aspartyl proteinase) on protein breakdown and structural integrity of sausage models (SMS+P) was investigated, resulting in the formation of a more fluid and less organized meat matrix that led to changes in water populations T2b2 and T22 compared with SMS. A very different protein degradation pattern between SMS and SMS+P was observed by means of SDS-PAGE and fluorescamine assay, supporting that some degree of protein aggregation is needed for the presence of the T22 population in fermented sausages.