聚乙烯醇活性薄膜中紫薯花青素和纳米二氧化钛的释放动力学分析

将紫薯花青素和纳米二氧化钛掺入聚乙烯醇中,通过溶液流延法制备聚乙烯醇活性薄膜。以紫薯花青素主要成分之一的矢车菊素衡量薄膜中紫薯花青素的释放规律,研究了聚乙烯醇活性薄膜中矢车菊素和纳米二氧化钛向含水食品模拟液、酸性食品模拟液、亲酯性食品模拟液和油性食品模拟液中的释放规律,并基于Fickian+一级动力学模型对试验数据进行拟合表征。研究结果表明:对比4种食品模拟液,聚乙烯醇活性薄膜中矢车菊素和纳米二氧化钛的扩散系数和释放比,在油性食品模拟液中最高,扩散系数分别达到5×10~(-11),1.29×10~(-13) cm~2/s,释放比分别达到0.966和0.357,然后依次为亲酯性食品模拟液和酸性食品模拟液,在含水食品模拟液中的扩散系数和释放比最低,扩散系数分别为1.34×10~(-11),0.85×10~(-13) cm~2/s,释放比分别降至0.25和0.121。聚乙烯醇活性薄膜中矢车菊素和纳米二氧化钛向4种食品模拟液中的释放规律能够用Fickian+一级动力学模型进行表征,且拟合精度R~2均达到0.98以上。通过Fickian+一级动力学模型拟合的4种食品模拟液中矢车菊素和纳米二氧化钛的释放曲线整体变化趋势相似,均呈先快速上升后逐渐平缓的趋势。     

聚乳酸抗菌包装中麝香草酚在食品模拟物中迁移规律

研究麝香草酚/聚乳酸包装材料中的抗菌剂麝香草酚在食品模拟物中的迁移行为。在4、10、20、30 ℃条件 下分别将麝香草酚/聚乳酸包装材料浸入蒸馏水溶液、体积分数4%乙酸溶液、正己烷溶液、体积分数10%乙醇溶液 中,通过紫外分光光度法测定食品模拟液中麝香草酚迁移量,分析温度和食品模拟物对麝香草酚迁移量的影响,在 实验数据基础上,采用Piringer方程建立麝香草酚迁移模型,分析验证迁移模型的合理性。结果表明：麝香草酚迁 移量随着迁移温度升高和迁移时间延长而逐渐上升直至平衡,且在4 种食品模拟物中麝香草酚的迁移量大小顺序为： 正己烷＞10%乙醇＞4%乙酸＞蒸馏水;根据幂律方程发现麝香草酚的迁移机制符合Fick扩散定律,且迁移方程扩散系 数随迁移温度升高而增大,分配系数与之相反;Piringer方程能够较好地描述麝香草酚迁移行为。在迁移实验的基础 上构建数学模型,进一步完善基于聚乳酸食品包装材料的迁移理论,以期更好地预测食品包装中麝香草酚的迁移。     

Controlled release of α-tocopherol,quercetin, and their cyclodextrin inclusion complexes from linear low-density polyethylene (LLDPE) films into a coconut oil model food system

Polymer additive migration into a food product is dependent upon numerous factors including the original concentration of the additive in the polymer, its solubility in the food, its diffusion coefficient in the polymer, its partition coefficient between the polymer and food, temperature, and time. The limited solubility of quercetin in linear low-density polyethylene (LLDPE) did not allow release from the film due to phase segregation of the quercetin in the bulk polymer. Increasing the molecular weight of α-tocopherol by β-cyclodextrin inclusion complexation can greatly reduce its diffusion coefficient in LLDPE. Ziegler–Natta and metallocene LLDPE contain different crystalline structure morphologies and diffusion path networking arrangements that allow for differences in additive release rates. Effective controlled-release packaging should combine β-cyclodextrin complexation of additives and polymer morphology control to target delivery of an optimal antioxidant concentration to achieve prolonged activity, resulting in extended shelf life foods.     

Determination of the mass transport properties of chemical additives in polypropylene material/simulated food system

The mass transport process (migration) of five additives from three different types of polypropylene (PP) films into selected food simulants was studied. The migration tests were carried out at different time-temperature conditions, and the concentration of additives in polymer matrix and food simulants were analysed by high-performance liquid chromatography (HPLC). With all data, the mass transport properties for migration kinetics (partition and diffusion coefficients) were determined. Results showed that the partition coefficient was affected significantly by the temperature and simulants’ properties, whereas little affected by the types of PP film and molecular weight of substance. The polarity, structure and shape of substances can also have an influence in their partition between the polymer matrix and food simulants. Additionally, comparison results between the experimental diffusion coefficients and the calculated values by Piringer model suggested that the current migration model with the default modelling parameters for PP does not describe realistically the diffusion coefficients of additives. The calculated diffusion coefficients were greater than the experimental values, as a consequence, the migration of chemical additives will be overestimated. For more realistic migration calculations, more accurate modelling parameters in Piringer model should be established and the effect of food on migration should be high interest in future work.     

分散染料在锦纶6薄膜中的扩散行为研究

选用大量分散染料对其在锦纶６薄膜中的分布及其扩散系数进行了测定分析，发现分散染料在锦纶薄膜中的扩散属于二元扩散模型。     

纳米金属/金属氧化物-聚烯烃食品包装膜中纳米成分迁移的扩散系数估算

为探讨Fick第二定律是否符合聚烯烃食品包装膜中纳米成分向食品模拟物的迁移规律,根据已有实验数据,基于Crank模型进行拟合,估算纳米金属/金属氧化物-聚烯烃食品包装膜中纳米成分的扩散系数,并分析温度、聚烯烃、纳米成分和食品模拟物对扩散系数的影响。结果表明：纳米成分向食品模拟物的迁移符合Fick第二定律。温度升高促进纳米成分的迁移,且温度与纳米成分扩散系数的关系符合Arrhenius公式。不同聚烯烃结构对扩散系数的影响不同;聚丙烯3 种结构中,纳米铜和纳米氧化锌在均聚共聚聚丙烯中的扩散系数最大。不同纳米成分质量分数对其扩散系数的影响不同。纳米成分与食品模拟物、聚烯烃之间的溶解度差异也会影响其向食品模拟物迁移。     

Characterizing the migration of antioxidants from polypropylene into fatty food simulants

The migration (diffusion and equilibrium) processes of antioxidants (AOs) from polypropylene (PP) films of different thicknesses into n-heptane and 95% ethanol as fatty food simulants were analysed at 20, 37 and 60°C. Heptane fully extracted the AOs from the polymer while a partition equilibrium described the migration to ethanol. The kinetics of migration were also studied via the diffusion coefficients. As expected, diffusion was found to be faster when the polymer was in contact with heptane, due to polymer swelling by the solvent. The kinetics of the process in ethanol was described by different theoretical expressions which are discussed. Equations disregarding partition equilibrium failed to describe the process and the diffusion coefficient values obtained through them were much smaller than the actual ones and dependent on film thickness. The results also showed the significance of food simulant selection in the analysis of food-packaging interactions and migration variability with thickness.     

Dependence of the effective diffusion coefficient of moisture with thickness and temperature in convective drying of sliced materials. A study on slices of banana, cassava and pumpkin

Several studies have indicated that effective diffusion coefficients of slices apparently vary with the thickness of the samples. Even though the effective diffusion coefficients have been observed to be dependent on the square of the slice thickness, a theoretical explanation to this behavior is not available to date. A theoretical model is formulated herein, in order to correlate effective diffusion coefficient of moisture in the slices with the slice thickness. Experiments are carried out for drying of slices of different thicknesses of banana, cassava and pumpkin in order to evaluate the effective diffusion coefficients. The model is found to describe the variation of the effective diffusion coefficient with slice thickness very satisfactorily. A possibility of the estimation of the axial and radial diffusion coefficients of moisture in the slices is also outlined.     

Experimental and theoretical study of LDPE versus different concentrations of Irganox 1076 and different thickness

This work presents a theoretical and experimental study on the specific migration process, describing the mass transfer of a model migrant Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (I-1076), an antioxidant commonly used in the polyolefins processing. Film samples (LDPE), with initial concentration of Irganox between 1000 and 6000 (mg/kg), and thickness of 50-190 ??m, were placed in contact with fatty (EtOH 95%) and aqueous (EtOH 10%) food simulants at 40 °C for 20 days, in order to obtain the concentration evolution in the food simulant which was measured by HPLC. On the other hand, a phenomenological model based on a resistances-in-series approach was developed considering the diffusion through the polymer film, natural convection in the food simulant and the thermodynamic equilibrium between the polymer and the liquid simulant phase. For the thickest films, the diffusion coefficient of I-1076 through the polymer phase was estimated varying between 1.95·10^− 13 (m² s^− 1) and 2.0·10^− 13 (m² s^− 1) at 40 ºC. On the contrary, the thinnest one shows a significant decrease of the diffusion coefficient value, which was evaluated in 1.0·10^− 14 (m² s^− 1). This modification can be explained by means of a crystal distribution and size in the thinnest polymer film prepared by CAST extrusion. The mathematical model developed is a tool for prediction and analysis which can be used to facilitate the characterization of polymers, and it could predict the response as packaging for food in a specific application.     

Determination of Sorbic Acid Diffusivity in Edible Wheat Gluten and Lipid Based Films

Edible films using wheat gluten as the structural matrix with or without different lipid components and pure lipid films were tested for sorbic acid retention properties. A diffusion mechanism following Fick's first law was identified. An experimental procedure was developed for determining the diffusivity coefficient of sorbic acid in edible films immersed in an aqueous medium. The effect of film composition and temperature was investigated. The diffusion coefficient of sorbic acid in a gluten based film was 7.6 × 10^?12 m²/sec. The addition of a lipid component such as acetylated monoglyceride led to a 50% reduction in diffusivity. In a pure lipid film such as beeswax the diffusion coefficient of sorbic acid was 2.7 × 10 ^?16m ²/sec. The effect of temperature could be described by an Arrhenius type model, with activation energy ranging from 30.0 to 39.8 kJ/mole.     

Use of a Mathematical Model to Describe the Barrier Properties of Edible Films

ABSTRACT: A study on the influence of the solubilization and diffusion process on the barrier properties of 4 different edible films is presented. The water and oxygen barrier properties of zein, alginate, casein, and chitosan films were measured at 25°C. A mathematical model was fitted to the experimental data to obtain quantitative information on both solubilization and diffusion process. Results suggest that alginate film, which shows the highest water and oxygen permeability coefficient, has both higher affinity with water and a higher macromolecular mobility than the other 3 films. The lowest water and oxygen permeability coefficient was detected for chitosan and zein films. The casein film has shown an intermediate behavior.     

A mathematical model of the effect of pH and food matrix composition on fluid transport into foods: An application in gastric digestion and cheese brining

The question of bioaccessibility of nutrients within a food matrix has become of increasing interest in the fields of nutrition and food science as bioaccessibility is the precursor to bioavailability. By analyzing the propagation of the wetting front of acidic water in raw carrot core and Edam cheese as model systems, we show that the diffusion of the acidic water is dependent on the pH of the gastric fluid and the food matrix. In addition, we demonstrate that the diffusion of NaCl during cheese brining is also dependent upon the concentration of the NaCl. This demonstrates that Fickian diffusion, along with a concentration dependent diffusion coefficient, is a valid model for describing concentration profiles in multiple food systems.Utilizing the diffusion rates found at various pH levels (1.50, 2.00, 3.50, 4.30, 5.25 and 7.00), we developed a model to describe the measured non-linear rate of soluble solid loss during digestion at various constant pH levels. Additionally, we have developed a model to predict the likely rate of soluble solid loss during digestion in the stomach where pH decreases with time. This model can be used to help understand and optimize the relationship between food structure/composition and food degradation in the human stomach, which may help in the development of novel foods with desired functionality.     

New methods to assess water diffusion in amorphous matrices during storage and drying

Water diffusion coefficient is an important parameter for food processing and stability, strongly influenced by the composition and the physical state of the matrix (amorphous glassy or rubbery/crystalline). In this study, two different methods to assess water diffusion in amorphous matrices were compared. First, an automatic sorption device was used to measure the water sorption kinetics of powders of maltodextrin DE21 and DE47 with defined shapes when equilibrating at different air relative humidity (0–60% at 25 °C). Calculation of water diffusion coefficients was done according to Crank’s and Weibull’s models, and it was not possible when powders undergo glass transition. In the second part of the study a thin film dryer was used to assess the drying kinetics of aqueous solutions of maltodextrin (DE 6-12-29-40). The Yamamoto’s model allowed calculating water diffusion as a function of water content and temperature, above and below glass transition temperature.     

Kinetics of release from kafirin films

Two separate studies were performed. The first studied release of two different preservatives (lactic acid and calcium propionate) from a biopolymer film to a model food with a water activity of a_w=0.95. The second investigated the release of four sugars (fructose, maltose, raffinose and stachyose) with different molecular weights from a biopolymer film to a model food with water activities ranging from 0.85 to 0.95. In both studies, the biopolymer films containing the release components were made from kafirin and placed on the model food, consisting of a gel made of gelatine, sucrose and water with well defined water activity. The amount of preservatives and sugars released from the film to the gel were monitored over time using HPLC at different depths in the model food.The release of preservatives was rapid in both cases, and a gradient of released substances had already formed after 2 h in the model food. The gradients levelled out with time. Calcium propionate had a somewhat faster release than lactic acid.The water activity of the model food had a large impact on the release of sugars. A slow release was observed in the model food with a_w=0.85, while a much more rapid release occurred in the model food with a_w=0.95. There was a limited diffusion depth in the model food with a_w=0.85, probably owing to a limited trial time, while the sugars in the model food with a_w=0.95 diffused deeper into the model food until the film was depleted of available sugars.     

From macroscopic to molecular scale investigations of mass transfer of small molecules through edible packaging applied at interfaces of multiphase food products

This paper presents a multi-scale approach to investigate mass transfer properties of edible films that integrates some published data and new original results. The transport of small molecules, such as water, between the different parts of multiphase food products leads to quality deterioration and thus requires the use of barrier edible films or coatings. Therefore, it is necessary to characterise the properties of both food and edible barriers, like the diffusivities of their respective migrants. Surface properties characterisation of edible films, composed of an iota-carrageenan matrix in association with a high melting point fat was investigated by goniometry and allows the determination of wetting and water absorption, with emphasis on the constituents functionality. Diffusion of a model probe using the FRAP (Fluorescence Recovery After Photobleaching) method is characterised by a critical water content threshold, inducing an increase of the molecular mobility, and better explains the role of glycerol, used as the plasticizer. This study brings information on the diffusion of a small molecule in the film. Further NMR (Nuclear Magnetic Resonance) spectroscopy investigation contributes to a better understanding and identification of the interactions between the polymer and the diffusant. Finally, FTIR-ATR (Fourier Transform InfraRed–Attenuated Total Reflectance) analysis enables to obtain the diffusion coefficient of the liquid water in the film. Such a multi-scale investigation highlights the permeation mechanism within edible barriers.Industrial relevanceSynthetic food packaging is usually used to prevent mass transfers of some molecules, such as moisture, gases, flavor compounds or solutes, between a food and its surrounding medium. In the case of multiphase food products, the development of edible films and coatings, applied between the different phases of this food, has a great potential to increase its shelf life. This article examines the different scale levels of investigation in order to determine the diffusivity of small molecules through these edible packaging.     

Measurement of transport phenomena of volatile compounds: A review

Measurement of the transport phenomena of volatile compounds is a central preoccupation in food flavour and is the subject of the present paper. After a theoretical reminder concerning transport phenomena, the methods used for the measurement of diffusion and mass transfer of volatile compounds are described with their principles, main advantages and drawbacks. These methods are illustrated by some results obtained for flavoured model food products.

Several methods characterized by the type of diffusion coefficient measured, the method basis, the scale at which diffusion is measured and the means used to detect the diffusing molecule, are available to determine diffusion coefficients.

To study the impact of the different factors influencing aroma release, kinetic parameters extracted from release curves obtained by sampling and analysis of the gas phase can be measured and compared. The coherence between experimental conditions and mathematical models used to estimate the parameters is of major importance.     

Measurement of effective diffusivities of ionic and non-ionic solutes through beef and pork muscles using a diffusion cell

A diffusion cell in conjunction with a new mathematical model was used to measure the apparent diffusion coefficients of sodium chloride, potassium nitrate and glucose through beef semitendinosus and pork longissimus dorsi muscles. The apparent diffusion coefficient was obtained within less than 180 min with a coefficient of variation less than 10% in most cases. The influence of temperature can be adequately explained by the Arrhenius-type law with activation energy between 19 and 26 kJ/mol depending on the diffusant. However, these values were not significantly different. Finally, we showed that the apparent diffusion coefficient of sodium chloride is not affected by the direction of the muscle fibre to the axes of diffusion while glucose diffusion parallel to the muscle fibre can be three times greater than diffusion at a right angle to the muscle fibre.