核磁共振技术在食品分析检测中的应用

核磁共振检测技术是一种新型的食品无损检测技术。介绍了核磁共振的基本原理和优势,综述了国内外核磁共振技术在食品中的水分、油脂、玻璃态转变、碳水化合物、蛋白质及品质鉴定等方面的研究进展,但该技术在实际应用中仍然存在一些问题,有待进一步研究。     

核磁共振技术在食品研究中的应用

介绍了核磁共振(NuclearMagneticResonance)技术的基本原理及其在食品分析和研究中的应用。     

Monitoring changes in feta cheese during brining by magnetic resonance imaging and NMR relaxometry

Magnetic resonance imaging (MRI) and NMR relaxometry were used to monitor changes in feta cheese during 169 h of brining at 4.8%, 13.0% and 23.0% salt solutions. Image and relaxation data were acquired to study salt uptake and water loss due to dehydration of cheese during brining. Saturation recovery and Carr-Purcell-Meiboom-Gill (CPMG) sequences were used to determine the longitudinal relaxation (T₁) and the transverse relaxation (T₂) times, respectively. Signal intensities of T₂ weighted images decreased during 169 h of brining. An excellent linear correlation between the average signal intensity and the water content was obtained (R² = 0.984). The T₁ values of cheese brined at 4.8% were almost constant but T₁ values decreased for both 13.0% and 23.0% salt brined cheeses. Analysis of the CPMG decays gave relaxation spectra containing two components which decreased during brining. The short component T_2a was highly correlated with salt content (R² = 0.974). Results showed that NMR and MRI can be used to follow salt uptake and changes in water content in cheese during brining.     

Investigation of the behaviour of chitosan microparticles as pH responsive hydrogels in the gastro-intestinal tract using magnetic resonance imaging

The objective of this research was to determine whether chitosan microparticles could be developed as potential satiety enhancing ingredients by investigating their swelling behaviour in the gastro-intestinal tract using magnetic resonance imaging (MRI). Previous work undertaken using a covalently cross-linked composite of chitosan and bovine serum albumin (BSA) showed this system swells in gastric conditions in vitro (Butler, Clark, & Adams, 2006). This paper describes the preparation and characterisation of chitosan/BSA microparticles cross-linked using 25 mM and 100 mM glutaraldehyde (GDA). 1.5% chitosan/15% BSA microparticles cross-linked with 25 mM GDA swell by 100% in simulated gastric conditions. We found an experimental correlation between the transverse NMR relaxation time, T₂, and swelling of the microparticles in vitro. Our study of four volunteers showed swelling of these microparticles in the human stomach, observed from increases in T₂ of the microparticles using non-invasive MRI. As such, our initial results, with 4 volunteers, suggest that this system could be used as a potential satiety enhancing agent in vivo as we would expect it to provide gastric distension due to swelling at low pH. Further studies with more volunteers would be necessary to confirm our initial findings.     

代谢组学在食品科学中的应用进展

代谢组学分析主要集中于对小分子代谢物综合分析,是对代谢靶标分析、代谢轮廓分析以及代谢指纹分析的进一步深化和融合.传统的食品分析主要分析蛋白质、脂肪、碳水化合物等,通过代谢组学技术,可在一种食品中检测到成百上千种不同的化学成分,从而为食品的鉴别、安全、加工、营养研究等提供更强大的数据支撑.文章综述了代谢组学的分析技术、样...     

食品添加剂在食品生产中的应用及监管

介绍了食品添加剂的定义及使用原则,指出了食品添加剂在使用过程中存在的问题,并对食品添加剂在食品生产中的应用及监管提出了建议。     

Postharvest structural changes of Hayward kiwifruit by means of magnetic resonance imaging spectroscopy

In the present study magnetic resonance imaging (MRI) was used to evaluate the effect of storage conditions, 0 °C and 90% relative humidity (RH) or 20 °C and 70% RH, on minimal structural changes of kiwi tissue. Storage time was 35 days at 20 °C and 65 days at 0 °C including shelf life. Ethylene and respiration were followed during the experiment as well as commercial quality parameters such as sugars and firmness. MRI images weighted for proton density (ρ) and transverse relaxation times (T₂), were recorded after 10, 20, 35, 55 and 65 days. A decrease of the diameter was clearly visible in samples stored at 20 °C after 3 weeks and a coarse contour of the pericarp appeared after 40 days. Accumulation of water in the pericarp was found, suggesting a migration towards the outer regions occurs and that the fruit water loss due to evapo-transpiration is slower than the migration process. Samples stored at 0 °C showed no relevant changes in dimension and structural features for the whole period considered except after removal to shelf life. The observed variations of the internal morphology were correlated with the transverse relaxation times of defined areas and with softening of fruits. Measured T₂ profiles showed double-exponential decays, a fast- and a slow-relaxing component, indicating the existence of two different types of water molecules within cellular tissues: strongly and weakly bound, respectively. The relation among MRI data, ethylene and softening is discussed.     

Quantitation by magnetic resonance imaging of heating of commercial baby foods in glass jars

This study demonstrates how magnetic resonance imaging can be used to quantitate the heating of commercially available baby foods as sold in glass jars either ‘on‐line’ during immersion in warmed water in the scanner's magnet, or ‘off‐line’ following microwave heating. The internal temperature distribution can be measured in 2‐ or 3‐dimensions with a precision of ±1.5 °C compared with fibre optical thermo‐probe measurements. Illustrative examples include jars of Heinz ‘Banana & Apple’, Sainsbury's ‘Organic Banana Rice Pudding’ and Cow & Gate ‘Organic Roasted Vegetable Lasagne’. Localised thermal lags induced by pieces of vegetable in the lasagne were observed during on‐line immersion heating. Importantly, the spatially heterogeneous heating by microwaves demonstrates the need for strong warnings about using microwave ovens for heating baby foods.     

食品科学与营养

介绍了食物、食品、营养的概念,论述了食品（食物）与营养的意义及食品与营养的关系。     

变频器在食品机械中的应用

介绍了变频器在食品机械中的几种典型应用,指出变频器在现代食品工业中具有广泛的应用优势.     

Void structure in textiles by nuclear magnetic resonance,Part I. Imaging of imbibed fluids and image analysis by calculation of fluid density autocorrelation functions

Void structure in textiles may be characterized by a variety of methods, including many based on nuclear magnetic resonance (NMR). The NMR techniques are based on the measurement of fluid distribution or diffusion within porous media, and are therefore particularly relevant for characterizing the void space that governs fluid interactions and movement within textile substrates. In this article, we describe the use of NMR imaging, also known as magnetic resonance imaging, to measure average void dimensions in textile fabrics. In addition to direct visualization using NMR images, void space may be analyzed by calculating the fluid density autocorrelation function. The advantages of both types of data analysis are discussed. These NMR techniques are applied to a water-saturated nylon fabric and the results compared to void sizes measured from optical microscopy.     

核磁共振(NMR)技术在油脂和食品中的应用

综述了核磁共振(NMR)技术最近几年来在油脂和食品中的一些应用，说明NMR是一种有效的方法，它准确度高，精密度和重现性好，而且效率高，节约人力，值得推广。     

Recent developments in the food quality detected by non-invasive nuclear magnetic resonance technology

ABSTRACT

Nuclear magnetic resonance (NMR) is a rapid, accurate and non-invasive technology and widely used to detect the quality of food, particularly to fruits and vegetables, meat and aquatic products. This review is a survey of recent developments in experimental results for the quality of food on various NMR technologies in processing and storage over the past decade. Following a discussion of the quality discrimination and classification of food, analysis of food compositions and detection of physical, chemical, structural and microbiological properties of food are outlined. Owing to high cost, low detection limit and sensitivity, the professional knowledge involved and the safety issues related to the maintenance of the magnetic field, so far the practical applications are limited to detect small range of food. In order to promote applications for a broader range of foods further research and development efforts are needed to overcome the limitations of NMR in the detection process. The needs and opportunities for future research and developments are outlined.     

Monitoring dry-curing of S. Daniele ham by magnetic resonance imaging

S. Daniele hams were collected at different stages during dry-curing and submitted to magnetic resonance imaging (MRI) according to the acquisition Spin-Echo sequences T1 and T2. The intensity of the MR signals in the images of the Semimembranosus, Semitendinosus, Rectus femoris and Biceps femoris muscles of the hams was computed and expressed in grey levels. Muscles were also submitted to traditional analyses, including a_w, soluble solids, sodium chloride, total and water soluble nitrogen. T1 and T2 MR signals well described the evolution of the phenomena occurring in the different muscles during dry-curing. MR signal acquired in T2 mode well correlated with traditional indicators in Semitendinosus, Rectus femoris and Biceps femoris muscles. Predictive models estimating the value of a_w, moisture, salt content and proteolysis extent on the basis of the MR signal intensity were proposed.     

Moisturization processes in living human skin studied by magnetic resonance imaging microscopy

Magnetic resonance imaging is a non-invasive, non-destructive and chemically specific imaging method widely used in medicine to reveal information about both tissue structure and function. It can measure water in tissue, but it has been difficult to achieve the necessary sensitivity and resolution when applying it to studies of the dry, thin stratum corneum. In this paper the use of magnetic resonance imaging to image the outer layers of the skin with a resolution of 0.06 mm is reported. Configuring the magnetic resonance imaging method in this way has made it possible for the first time to actually 'see'directly the moisturization in the stratum corneum. It is no longer necessary to rely upon methods which can only show side-effects of moisturization, such as changes in the appearance of the skin cells. As magnetic resonance imaging is harmless, it can be used repeatedly on the same skin and so produce a series of stills, or a time-lapse video, clearly showing the actual process of moisturization and related phenomena. The behaviour of skin has been observed during both hydration and dehydration; the two processes follow different time courses. Two layers have been observed in the stratum corneum, which appear to be different when the skin is hydrated.
For the first time the actual surface of normal skin has been revealed on magnetic resonance images.     

A new magnetic resonance imaging approach for discriminating Sardinian sheep milk cheese made from heat-treated or raw milk

The evaluation of milk heat treatment on dairy products via reliable analytical methods is a challenging issue that involves both industrial and fundamental research. We describe a new magnetic resonance imaging (MRI) protocol for discriminating Sardinian sheep milk cheese originating from heat-treated or raw milk. Thirty-six samples (18 pecorino cheeses manufactured from heat-treated milk and 18 Fiore Sardo cheeses made from raw milk) were investigated by means of MRI and bi-exponential signal decay analysis. The protocol is capable of discerning cheeses by virtue of the different distribution of the transversal (T₂) relaxation time constant. Cheeses from heat-treated milk showed a significantly higher area fraction (≈70–80%), corresponding to the fast relaxing water protons (T₂ ≈ 9 ms), compared with raw milk cheeses, whereas the opposite was observed for the long T₂ (T₂ ≈ 35 ms) proton population. The MRI protocol described is rapid and nondestructive, and it provides statistically significant discrimination between ewe milk cheeses made from heat-treated and raw milk.