Real-time detection of water dynamics in abalone (Haliotis discus hannai Ino) during drying and rehydration processes assessed by LF-NMR and MRI

To detect the water dynamics in abalone during drying is essential for the textural quality improvement, however, sufficiently rapid and nondestructive methods of abalone moisture monitoring are currently lacking. In this study, water changes in abalone during drying and rehydration processes were assessed using low field nuclear magnetic resonance and magnetic resonance imaging. A close correlation was observed between A_Total and the total moisture content, and a prediction model with high correlation (R²?=?0.935) was established. Furthermore, good correlations (R²?>?0.950) between hardness, chewiness, rehydration ratio, and T₂₂ relaxation of dried abalone were observed during the rehydration process.     

Moisture conversion and migration in single-wheat kernel during isothermal drying process by LF-NMR

Conversion among different moisture-binding types of single Hebei wheat kernels during isothermal drying processing at 60?°C was studied by low field nuclear magnetic resonance (LF-NMR), and moisture migration was studied by MRI. Water inside wheat kernels exists in four types: chemically combined water (T₂₁), strong bound water (T₂₂), loosely bound water (T₂₃), and free water (T₂₄). A new method to obtain the contents of different moisture-binding types is forwarded according to the transverse relaxation time distribution curve of dried wheat kernels. Moisture conversion inside wheat kernels during drying occurs mainly through the following mechanisms: high-temperature drives T₂₄ to diffuse to lower moisture areas and transform into other moisture-binding types, and moisture-gradient drives T₂₂ to transform into T₂₄. The drying process can be divided into two stages. Moisture migrates from endosperm to epidermis during drying. As the drying rate of the wheat kernel significantly decreases, the drying conditions and parameters need to be adjusted to improve the drying rate while ensuring the quality of wheat kernels.     

Use of low-field-NMR and MRI to characterize water mobility and distribution in pacific oyster (Crassostrea gigas) during drying process

Low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) were used to monitor the water mobility and distribution of Pacific oyster during drying process. The results show the mobilities of bulk, immobilized, and free water were reduced, and the immobilized water was removed dramatically. T₂-weighted images displayed the water decrease from the external surface to inner center of oyster during drying. In addition, excellent correlations between the total moisture content and T₂₂ and A₂₂ were observed with coefficients 0.9777 and 0.9832, respectively. Principal component analysis showed the drying degree of oyster could be monitored based on raw relaxation data. Thus, the result revealed that LF-NMR and MRI have great potential in assessing water mobility and distribution in oyster during drying process.     

Effects of gluten and moisture content on water mobility during the drying process for Chinese dried noodles

To investigate the water mobility during a drying process, noodles were prepared with different gluten contents (10.0%, 12.5%, 15.0%, 17.5%, 20.0%, 22.5%, or 25.0%) and moisture contents (30%, 32%, or 34%), and dried on a food moisture analysis technology platform. Three types of water were deduced from relaxation signals measured by low-field nuclear magnetic resonance (LF-NMR) spectroscopy. Peak time T₂₂ increased with gluten and moisture content but decreased with drying time from 4–6 to 1.0–1.7?ms after 1.5?h. Gluten content mainly affected the drying rate (DR) in the middle drying period, whereas initial moisture content had an influence in the middle drying period and final drying period.     

Effect of hot-air oven dehydration process on water dynamics and microstructure of apple (Fuji) cultivar slices assessed by LF-NMR and MRI

Abstract

Non-destructive analysis of water dynamics during drying is of importance for quality control of food products. In this study, different water dynamics and migration in Fuji apple slices dried at various hot-air oven temperatures, i.e. 50, 60, 70, and 80?°C and air velocity at 0.2 m/s were monitored using low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI). Multi-exponential fitting of the transverse relaxation T₂ parameter demonstrated four distinct water peaks in all samples corresponding to strongly bound, lightly bound, entrapped/immobilized, and free water as follows: T₂₁ in the range of 0.01–1?ms, T₂₂ in the range of 1–10?ms, T₂₃ in the range of 10–100?ms, and T₂₄ in the range of 100–1000?ms, respectively. The water content was measured and analyzed by the traditional technique using the oven drying method. The overall results were highly significant, depicting that the transverse relaxation times T₂₄, signal per mass of the free water A₂₄, and water content significantly decreased (p< 0.05), while the color (L*, a*, b*) and shear force (SF) curves increased with extended drying. Furthermore, good correlations were observed between the LF-NMR parameters and color, water content, and SF in differently processed samples during the dehydration process. Scanning electron microscopy (SEM) and MRI provided the structural changes and spatial water distributions during the drying process. LF-NMR exhibited great potential in evaluating the various water dynamics and quality of Fuji cultivar apples during the drying process.

Abbreviations: AA: ascorbic acid; ANOVA: analysis of variance; CPMG: Carr-Purcell-Meiboom-Gill; DW: distilled water; F: Fuji; LF-NMR: low-field nuclear magnetic resonance; MRI: magnetic resonance imaging; SE: spin-echo; SEM: scanning electron microscopy; SF: shear force; SIRT: simultaneous iterative reconstruction technique; TE: echo time; TR: repetition time.     

LF-NMR online detection of water dynamics in apple cubes during microwave vacuum drying

ABSTRACT

In this study, changes in various states of water in apple cubes were assessed using low-field nuclear magnetic resonance (LF-NMR) during microwave vacuum drying. Apple cubes were dried at different microwave power levels (100, 150, and 200?W). Indicators including moisture content and water activity were measured. The Carr–Purcell–Meiboom–Gill (CPMG) sequence was used to measure transverse relaxation times (T₂). The results showed that three water fractions with different T₂ relaxation times (around 11, 126, and 1335 ms) were detected in fresh apples, which corresponded to different cell compartments. The transverse relaxation time of bulk water (T₂₃) and the signal per mass of the bulk water (A₂₃/g) decreased significantly with increasing drying time at different microwave power levels. The signal per mass of the total water (A_Total/g) had significant correlation with the total moisture content (R²?=?0.9919). Furthermore, good correlation (R²?=?0.9799) between water activity and NMR parameters based on partial least square regression model were observed. This research revealed that LF-NMR spectroscopy, a nondestructive technique, can detect the changes of water in different populations in the matrix.     

干燥过程中PVC树脂水含量的控制

介绍了影响PVC树脂干燥的主要因素,分析了旋风干燥床出口温度(T1)标准偏差、工序能力指数及作直方图来推算收集数据的各种特征值,如果T1的设定值与实际值发生偏移,要采取相应措施,以免影响PVC树脂质量。     

Water status and distribution in shiitake mushroom and the effects of drying on water dynamics assessed by LF-NMR and MRI

Abstract

Water status and distribution in shiitake mushroom and the effects of drying temperature on water migration were investigated by low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) technique. Three water components assigned to bound, immobilized water and free water were observed in fresh shiitake mushroom by LF-NMR, and higher moisture content was found in the lamella and outer layer of stalk by MRI. During drying, the transverse relaxation time and peak area of immobilized and free water in pileus significantly decreased. Higher drying temperature could promote the changes in water mobility and population. MRI results revealed the water evaporated from external surface of shiitake mushroom, then the water in inner region migrated to the surface during the drying. The drying properties, color and shrinkage of shiitake mushroom were also measured. The strong correlation between moisture content and total peak area of water with a coefficient of 0.9792 revealed the potential of LF-NMR as a rapid and nondestructive method to monitor drying degree of shiitake mushroom.     

Online measurement of moisture content,moisture distribution,and state of water in corn kernels during microwave vacuum drying using novel smart NMR/MRI detection system

Moisture content is unevenly distributed and hard to measure when agricultural products are dried using microwave drying. A low-field nuclear magnetic resonance/imaging (NMR/MRI) and microwave vacuum drying (MVD) combination equipment was developed. The residual moisture content, distribution, and state of water (free, immobilized, and bound) in fresh corn kernels during MVD were quickly measured in real time. NMR results indicated that the amplitude of free and immobilized water decreased very rapidly at the early stage of MVD, while the amplitude of bound water experienced a similar rapid decrease at the last stage. MRI results indicated that the moisture content was always distributed unevenly during MVD, especially at the early stage. The moisture distribution tended to become uniform when drying progressed and the bound water became dominant. The residual moisture content of corn kernels and integral (total) amplitude of NMR were found to fit well with a linear model (R²?>?0.991, P?相似文献   

Matching of the water states of products and zeolite during contact adsorption drying

The mixing of dehydrated zeolites with product particles leads to drying of the product, owing to the decrease in relative humidity of the environment and increase the temperature of the mixture, due to the release of adsorption heat. The analysis of the conventional one-stage contact drying process showed a significant mismatching in the water states of the product and the zeolite during drying. A two-stage drying process is proposed for harmonization of the water state of both product and sorbent. The significant advantage of the two-stage drying over one-stage regarding the degree of drying of the product, the utilization of the zeolite adsorption capacity and the duration of the process were experimentally confirmed.     

Investigation on water distribution and state in tobacco leaves with stalks during curing by LF-NMR and MRI

The water distribution and state in tobacco leaves with stalks and without stalks during curing were measured by low-field nuclear magnetic resonance and imaging. Results showed that, moisture content of the stalk and midrib was higher than that of the lamina. Only immobilized and free water were found in the midrib of fresh tobacco leaves, whereas the bound water was found in the lamina and stalk. In addition, the mobility of each water state in the stalk and midrib was stronger than that in the lamina. Water migrated from the stalk to the lamina via the midrib during curing, which resulted in a higher proportion of free water in the lamina and a lower drying efficiency of tobacco leaves with stalks than those of nonstalks.     

Differences between constant and intermittent drying in surf clam: Dynamics of water mobility and distribution study

Low-field nuclear magnetic resonance (LF-NMR) has been increasingly popular as analytical tools for evaluating the dynamics of water mobility and distribution. In this study, dynamics of moisture mobility and constitution of surf clam during constant drying process and intermittent drying process were evaluated by LF-NMR, while the differences of physical and chemical indexes were measured. Intermittent drying improved the product quality of clam, such as moisture content, shear force, color indices, sugar content, peroxide value, thiobarbituric acid value, and the bulk water ratio, which were closely related with moisture distribution and microstructure. The moisture constitution of constant drying process and intermittent drying process were distinctly different. Tempering process reduced drying time and resulted in lower moisture content in dried surf clam. In the meanwhile, the boundary between A₂₁ and A₂₂ was acquired by LF-NMR, revealed that bound water and immobilized water transformed from each other. During tempering process, the myofibril stretched out, verifying that moisture approached a relatively homogeneous. In addition, R² value reached 0.9897 and 0.9926 for calibration and validation, respectively, displaying good linear correlations between the T₂₁ parameters and moisture content. This study interpreted the dynamics of water mobility and distribution on the proton level to explain the reason that tempering processes to improve physicochemical indexes of surf clam.     

益生菌在喷雾干燥过程中的活性变化与保护策略

肠道菌群对于人体健康具有重要影响。口服足量的活性益生菌,有助于缓解急慢性肠炎、治疗腹泄、改善消化,已在临床治疗中得到一定应用。在食品市场上,益生菌干粉制剂亟需一种生产成本低、制粉简便的生产方法。喷雾干燥的生产能力强、制粉快速,但干燥过程中,雾化液滴经历一个快速升温与脱水过程,对其中的益生菌带来热胁迫、脱水胁迫、氧化胁迫等多种不利因素,造成菌体活性的大量损失。而喷雾干燥塔的结构,使塔内的液滴干燥过程难以追踪,不利于研究益生菌的失活历程以及探索益生菌与载体材料间的相互作用。本文从雾化液滴在干燥塔内的干燥历程着眼,回顾了益生菌活性随液滴干燥动力学变化的趋势,讨论了益生菌在喷雾干燥中经受的亚细胞结构损伤与功能性损伤,并系统总结了目前文献中报道的提升干燥后益生菌活性的主要方法,包括提升菌体耐受性、优化喷雾干燥条件和采用合适的保护性载体,并着重阐述了载体材料与益生菌细胞间的相互作用关系以及干燥历程的重要影响。文章指出为最大程度上保存喷雾干燥粉末中益生菌的活性,应综合微生物、干燥过程与食品化学（材料学）等领域的保护策略,设计一体化统合生产方案。依据微生物-保护载体间的相互作用设计高效保护配方载体,研发统合从微生物细胞培养至粉末储藏的新型生产工艺,是实验室及工业中合理设计工业级喷雾干燥过程、大量生产高活性益生菌制剂的关键。     

Dielectric properties of thermosonically treated Agaricus bisporus slices during microwave vacuum drying and correlation with the water state

Abstract

The dielectric properties of thermosonically treated Agaricus bisporus slices during microwave vacuum drying were determined, by using a network analyzer and an open-ended coaxial-line probe at microwave frequency (915 and 2450?MHz). The permittivity at 25?°C was also correlated to the water state determined by low field nuclear magnetic resonance (LF-NMR) analysis. Results showed that the dielectric constant ε' and loss factor ε″ of A. bisporus slices were affected significantly by the composition of water state in the sample. Thermosonic pretreatment enhanced the influence of semi-bound water (M₂₂) and bound water (M₂₁) on the permittivities in sample slices during microwave vacuum drying (MVD). The dependency of permittivities on the moisture content and temperature at 915 and 2450?MHz for thermosonically treated A. bisporus samples could be described by third-degree polynomial models, with R² higher than 0.998. Infrared thermal imaging analysis confirmed that thermosonic pretreatment is a potential technology to promote the uniformity of A. bisporus slices during the MVD process.     

污泥深度脱水调理剂对污泥干化过程中含硫气体释放的影响

采用5种复合调理剂改善污泥脱水性能,制得深度脱水泥饼。通过检测N₂气氛下,不同干化温度（100℃、200℃）,停留时间（30 min、60 min）时,不同调理脱水污泥含水率的变化情况,以及含硫气体的种类和释放量,探讨不同调理剂对干化过程中含硫气体释放特性的影响。结果表明,提高温度、延长时间都可以有效降低污泥的含水率;原污泥干化过程释放的主要含硫气体为H₂S和SO₂,其总量占含硫气体的82.4%;FeCl₃+CaO和H₂SO₄+FeSO₄+H₂O₂+CaO复合调理剂调理脱水泥饼在干化过程中SO₂释放量占原污泥释放量的40.3%和40.6%,H₂S则基本没有释放;H₂SO₄+FeSO₄+H₂O₂+CaO调理脱水污泥在100℃和200℃干化过程中的总硫释放量分别占原污泥总释放量的75.0%和45.6%,该复合调理剂在有效提高污泥脱水性能的基础上,能最大限度地抑制含硫气体的释放。     

过程优化控制技术在SPVC干燥过程中的应用

阐述了采用"悬浮干燥过程优化控制技术"改造SPVC干燥装置的情况。运行数据表明,该技术提高了旋风干燥塔塔温控制精度、悬浮树脂成品的优级品率及挥发物指标。     

Drying characteristics and water dynamics during microwave hot-air flow rolling drying of Pleurotus eryngii

Abstract

The aim of this study was to improve the drying uniformity and quality of Pleurotus eryngii by using the combination of microwave drying and hot-air flow rolling drying. The moisture content, drying uniformity, and water migration of P. eryngii during microwave hot-air flow rolling drying (MARD) were analyzed in detail. The temperature distribution images were obtained via infrared thermal imaging techniques and the relationship between relaxation time and signal amplitude were obtained via low-field nuclear magnetic resonance analysis and imaging (LF-NMR/MRI). The curves of signal amplitude with moisture content changes were fitted by a linear model with good linearity correlation. It was found that the hot-air and rolling bed could improve the drying uniformity of microwave drying. And the free water was found to transform into immobilized water and bound water during the drying process. Only a small amount of water was left in the dried P. eryngii in the final stage. The results could provide supportive information for improving the uniformity and quality of the drying processes of the edible fungi.     

Modeling and simulation of the drying process of natural gas pipeline using vacuum drying method

Abstract

Vacuum drying is one of the most effective methods to protect submarine natural gas pipes from blockage caused by hydrate and internal corrosion. This article presents a model for analyzing the mass, momentum, and energy transfer processes in pipeline drying with vacuum drying method. Model of the evaporation rate of liquid water is derived from Hertz–Knudsen–Schrage equation. Finite volume method is employed to discretize the governing equations with an upwind implicit scheme in present work, and 2nd order upwind scheme for energy equation is adopted to weaken numerical dissipation. Non-linear algebraic equations after discretization are solved by Newton-Raphson method. Reliability and accuracy of this model are validated via three experimental cases. Numerical results coincide well with the experimental data, and the relative errors of the calculated drying time are 1.7% in Case 1, 1.2% in Case 2, and 5.5% in Case 3. Finally, the dynamic characteristics of the vacuum drying process are analyzed such as dynamic distributions of pressure, temperature, mass flow rate, and liquid holdup. Mathematical model and algorithm developed in present work provide understanding and insights of the vacuum drying process, which aids in determining cost-effective pipeline drying scheme.     

Relationships between transpiration,water loss,and air conditions during physiological drying

Tree transpiration can cause a rapid decrease in the moisture of tree trunk after felling. In this study, the physiological drying of poplar logs was examined as a result of transpiration. Experiments were conducted on poplar trees with and without canopies and where the water supply from the roots was blocked. The effect of transpiration on the drying process and the relationships between transpiration, water loss, and air conditions were investigated. Statistical analysis of the data showed that the moisture content (MC) decreased significantly as a result of physiological drying at a rate of 5.65% MC/day within 3 days, 3.85% MC/day within 5 days, and 2.30 MC/day within 9 days. The transpiration rate of the trees was positively correlated with the moisture loss. Leaf transpiration of control trees and those where access to water was blocked was strongly and similarly affected by air conditions, although the water-blocked treatment resulted in a significantly lower transpiration rate. The transpiration rate and stomatal conductance increased as relative humidity increased and as vapor pressure deficit decreased. When transpiration-mediated water loss occurred, the temperature difference between the air and leaf surface was approximately 1–3°C. The results indicate that transpiration is the main driving force that reduces water during physiological drying, and the main factors that influence this process are the air conditions.     

Improvements in the drying process for wet-spun chitosan fibers

Chitosan fibers were wet spun from a 6% by weight chitosan in 3% by volume acetic acid solution. The fibers were collected as a 20 filament yarn intended for use as a chaff substrate. The yarn had to be sufficiently dry following spinning to allow for winding and subsequent separation of the filaments. Drying of the yarn was attempted using various techniques including direct and radiant heat, forced air, and chemical drying agents. Product yarns were analyzed for ease of separation of the filaments, as well as comparison of mechanical properties. Individual fibers were evaluated on the basis of moisture content, surface morphology and fiber diameter. Results indicate that the particular drying method or agent used has a considerable impact upon all of the characteristics listed above. A methanol dry bath was found to provide optimum drying of the chitosan yarn, producing filaments with low moisture content that separated easily from one another. Methanol drying yielded chitosan fibers with smaller diameter, superior surface smoothness and superior mechanical properties to fibers dried using forced air, heat, or other tested drying agents such as acetone and isopropanol. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1435–1444, 1998