Effects of antioxidants and humidity on the oxidative stability of microencapsulated fish oil

The effects of various antioxidants and RH on the oxidative stability of microencapsulated fish oil powder were investigated using PV and thiobarbituric acid tests. The micorencapsulation process provided high encapsulation efficiency (≥88% of extractable fish oil). Without antioxidants, the encapsulated fat was 10 times more stable against oxidation than the surface fat, as determined by PV. α-Tocopherol, which is a lipophilic antioxidant, showed a greater antioxidative effect in both surface and encapsulated fats than ascorbyl palmitate, which is an amphiphilic antioxidant. According to TBARS values, the longest lag period was observed at 0% RH. Addition of >200 ppm α-tocopherol in a 10–30% RH range prolonged the oxidative stability of the microencapsulated fish oil powder.     

Drying characteristics and modeling of yam slices under different relative humidity conditions

The drying characteristics of yam slices under different constant relative humidity (RH) and step-down RH levels were studied. A mass transfer model was developed based on Bi-Di correlations containing a drying coefficient and a lag factor to describe the drying process. It was validated using experimental data. Results showed that the drying air with constant RH levels of 20, 30, and 40%, temperature of 60°C, and air velocity of 1.5 m/s had an insignificant effect on drying time. This phenomenon was likely attributed to the fact that higher RH led to a rapid increase in sample’s temperature. The higher sample temperature could provide an additional driving force to water diffusion and thereby promote the moisture movement, which could minimize the negative effect of lower the drying rate in the initial drying stage. Applying air with 40% RH for 15 min in the initial stage achieved the desired color and reduced the drying time by 25% compared to the drying time under continuous dehumidification from an initial RH of 40%. Using the developed Bi-Di correlation, the estimated Biot number, effective moisture diffusivity, and mass transfer coefficient ranged from 0.1024 to 0.1182, 1.1133 × 10^?10 to 8.8144 × 10^?9 m²/s, and 1.8992 × 10^?9 to 1.7364 × 10^?7 m/s, respectively. A rather high correlation coefficient of determination (R² between 0.9871 and 0.9971) was determined between the experimental and predicted moisture contents. The present findings contribute to a better understanding of the effect of relative humidity on drying characteristics. The developed Bi-Di correlation provided a new method to determine the effective diffusivity of moisture in drying.     

The importance of critical relative humidity—temperature relationship on design of rotary dryers for fertilizers

Fertilizer salts are sensitive to the humidity of the surrounding air; above certain relative humidities, they will absorb water. The humidity above which they absorb water is defined as critical relative humidity (CRH). The CRH decreases with increasing temperature.Fertilizer drying usually takes place at relatively high temperatures to facilitate heat exchange. The optimum drying effect is obtained only when the CRH of the product is sufficiently greater than the actual relative humidity (RH) of the air. A method that takes into account both the heat exchange and the CRH of the material has been developed for designing rotary dryers for fertilizers. A computer program is available that supports this design procedure.     

Effect of outlet drying temperature and milk fat content on the physicochemical characteristics of spray-dried camel milk powder

Abstract

A composite face-centered experimental design was used to investigate the influence of spray drying conditions on the physicochemical characteristics of camel and cow milk powders. Response surface methodology (RSM) was deployed to appraise the effects of these processing parameters (the outlet drying temperature and the milk fat content) on water activity (a_w), glass transition temperature (T_g), bulk density, and free fat quantity. According to RSM analysis, it was noticed that the a_w and the T_g were primarily influenced by the outlet drying temperature instead of by milk fat content. Our results highlighted the negative effects of milk fat content and of the outlet drying temperature on the bulk density as well as on the free fat quantity of camel milk powder. Likewise, our findings underlined the negative effect of the outlet drying temperature on the bulk density of cow milk powder. However, the increase of fat content has led to the overexposure of fat at the free surface of the cow milk powder. Our results suggested a marked similarity of the overall thermodynamic behavior of both milks, during drying. Nevertheless, some differences were highlighted regarding the structuring of the particles of camel milk powder.     

相对湿度对单组分室温硫化有机硅密封胶硫化性能的影响

考查了相对湿度对不同硫化体系、不同填料体系的单组分室温硫化(RTV-1)有机硅密封胶硫化性能的影响。结果表明:相对湿度对三种硫化体系的5种有机硅密封胶的硫化性能均有明显的影响。随着相对湿度的增加,脱酸型和脱醇型(填料为Si O2)有机硅密封胶的表干时间缩短、消粘时间延长、硫化深度增加;脱酮肟型(填料为Si O2和CaCO3)产品的表干时间缩短、消粘时间基本不变、硫化深度增加;脱醇型(填料为CaCO3)产品的表干时间延长、消粘时间延长、硫化深度增加。SJS668(脱酸型)和SJS9200(脱酮肟型,填料为Si O2)在相对湿度为20%~95%的条件下均可以施工,但相对湿度低时需延长养护时间;SJS5500(脱醇型,填料为Si O2)适宜施工的相对湿度为35%~65%;SJS6300(脱醇型,填料为CaCO3)和SJS3300(脱酮肟型,填料为CaCO3)适宜施工的相对湿度为35%~80%。     

Effect of Humidity on NPK Fertilizer Drying

ABSTRACT

The drying process within rotary coolers during the manufacture of granular NPK fertilizer plays an important role in the production of fertilizer granules possessing both a low moisture content and low caking propensity. A theory for fertilizer drying has been developed which takes into account the low critical relative humidity of complex fertilizer found at high temperature. The theory proposes that the gradient between the partial vapour pressure of moisture in the air and the vapour pressure moisture adjacent to the surface of the fertilizer granule, is the rate controlling stage in the drying of hot granular fertilizer rather than the internal diffusion of moisture within the particle.     

Effect of Humidity on NPK Fertilizer Drying

The drying process within rotary coolers during the manufacture of granular NPK fertilizer plays an important role in the production of fertilizer granules possessing both a low moisture content and low caking propensity. A theory for fertilizer drying has been developed which takes into account the low critical relative humidity of complex fertilizer found at high temperature. The theory proposes that the gradient between the partial vapour pressure of moisture in the air and the vapour pressure moisture adjacent to the surface of the fertilizer granule, is the rate controlling stage in the drying of hot granular fertilizer rather than the internal diffusion of moisture within the particle.     

环境湿度对AlH_3稳定性的影响

为评价环境湿度对AlH3稳定性的影响,采用干燥器平衡法及动态吸湿性分析法研究了AlH3的吸湿水解过程,获得AlH3的等温吸湿曲线以及不同温度下的临界相对湿度(CRH)。采用扫描电镜(SEM)、X射线粉末衍射仪(XRD)及有机元素分析仪对不同环境湿度下的AlH3及其水解产物进行表征。结果表明,在环境湿度小于临界相对湿度的条件下,AlH3的稳定性较好;当环境湿度大于临界相对湿度时,AlH3会发生明显的水解反应,并在晶体表面逐渐生成Al(OH)3,同时AlH3的临界相对湿度与环境温度呈反比。     

Oxidative stability of fat substitutes and vegetable oils by the oxidative stability index method

Oxidative Stability Index (OSI) of carbohydrate fatty acid polyesters, fat substitutes and vegetable oils were measured with the Omnion Oxidative Stability Instrument according to the new AOCS Standard Method Cd 12 B-92 (The Official Methods and Recommended Practices of the American Oil Chemists' Society, edited by D. Firestone, AOCS, Champaign, 1991). The stability of crude and refined, bleached and deodorized (RBD) vegetable oils (soybean, hydrogenated soybean and peanut) were determined at 110°C. In addition, OSI times for sucrose polyesters of soybean oil, butterfat, oleate:stearate and methyl glucoside polyester of soybean oil were determined in the absence and in the presence of 0.02 wt% antioxidants, [Tenox TBHQ (tertiary butylhydroquinone, Tenox GT-2 (from Eastman Chemical Products (Kingsport, TN); and vitamin E (from BASF, Wyandotte, MI)], and the results were compared with those of vegetable oils. Crude oils were most stable (20.4–25.9 h), followed by RBD oils (9.3–10.4 h) for soybean and peanut oils, respectively, and fat substitutes (3.8–6.8 h). Overall, Tenox TBHQ was the best antioxidant for improving the oxidative stability of both vegetable oils and fat substitutes. The sucrose polyester made with oleic and stearic acid was more stable than fat substitutes containing more polyunsaturated fatty acids, such as those from soybean oil, or from short-chain fatty acids, such as from butterfat. Antioxidants enhanced the stability of RBD oils (222% increase) and synthetic fat substitutes (421–424% increase) more than that of crude oils (33% increase). The shapes of the induction curves, not the actual OSI times for fat substitutes and vegetable oils, were similar and sharply defined.     

Effects of oil-droplet diameter on the stability of squalene oil in spray-dried powder

ABSTRACT

Effects of the oil-droplet diameter and emulsification with polymerized sodium caseinate (PNC) on the stability of squalene oil (SQ) retention in spray-dried powder were investigated. The SQ droplet diameter significantly affected the stability of the oil in spray-dried powders. The degradation behavior of SQ powders at 105°C was correlated using the Avrami equation. This oxidation mechanism may occur because of the propagative transfer of radical oxidation between oil-droplet particles. SQ emulsified with 5?wt% PNC and small oil droplets had better oxidative stability when compared with 3?wt% sodium caseinate.     

The effect of relative humidity gradient on water vapor permeance of lipid and lipid-hydrocolloid bilayer films

The water vapor (WV) permeance of lipid and lipid-hydrocolloid films exposed to relative humidity (RH) gradients of 100–0%, 100–50%, 100–65% and 100–80% RH were determined. The lipids used were beeswax (BW) or a blend of BW and acetylated monoglycerides (AG). Hydrocolloids used were methylcellulose, carboxymethylcellulose or ethylcellulose (EC). All films, except those containing EC, exhibited increased water vapor permeance as the RH gradient was reduced by raising the low-end RH. This increase in permeance was apparently caused by hydration and swelling across the entire film thickness, thus facilitating water movement through the film. Because of its hydrophobicity, EC likely lessened this swelling. Knowledge of the WV properties of edible films at relatively small gradients in the upper half of the RH spectrum, such as those used in this study, is useful because these conditions are far more common to foods than are the 100–0% gradients that are often used when evaluating films. Even though the WV permeance of BW and BW/AG films increased greatly at the 100–80% RH gradient, as compared to gradients ranging from 100–65% to 100–0%, they still possess WV barrier properties sufficient to be useful for foods.     

Effect of the microstructure on the stability of red onion microcapsules

The effect of microstructure on the stability of red onion encapsulated by two processes: (a) spray drying and (b) spray freezing into liquid cryogenic, was evaluated in this work. Water sorption isotherms and glass transition temperature of microcapsules conditioned at various water activities were determined and coupled to evaluate conditions of storage stability. The stability of red onion microcapsules was influenced not only by water activity increase but also by microstructural differences between the two types of microcapsules. Critical water content was a useful tool to establish adequate storage conditions for red onion microcapsules.     

Determination of oxidation stability of soybean oil with the oxidative stability instrument: Operation parameter effects

Operation parameters of the oil stability index instrument were evaluated to determine their effect on the oxidative stability of commercial soybean oil. A factorial design was developed to evaluate the following three parameters, each at two levels, sample weight (2.5 or 5.0 g), conductivity tube temperature (20 or 30°C), and air flow rate (12 or 20 L/h), for a total of eight observations. Significance testing indicated that sample size and air flow rate affected oil oxidative stability independently (P<0.001), but not in combination. The conductivity tube temperature did not affect the oxidation stability index. Presented at the 1993 American Oil Chemists’ Society Meeting in Anaheim, California.     

Wang-Landau Monte Carlo simulation of capillary forces at low relative humidity in atomic force microscopy

A lattice gas model is used with Wang-Landau Monte Carlo sampling to predict the capillary force between a model of an atomic force microscopy (AFM) probe and a smooth surface as a function of separation, relative humidity (RH), and tip hydrophilicity. Completely wetting AFM tips exhibit a maximum in the capillary force as the RH increases, while the magnitude of the capillary force in the presence of partially wetting and partially drying tips is relatively independent of the RH. Capillary forces can also be significant in low RH environments and should not be discounted in AFM studies involving hydrophilic surfaces.     

Effect of processing on the composition and oxidative stability of coconut oil

The effect of various processing procedures on the composition and oxidative stability of coconut oil has been studied. The crude oil is relatively stable but major reductions in oxidative stability occur during the bleaching of oil degummed with phosphoric acid; during alkali refining; during the deodorization of oil degummed with citric acid and bleached; and during the deodorization of oil processed with a combined phosphoric acid degumming and bleaching operation. The reasons for the loss of oxidative stability during processing are discussed with reference to changes in the composition of the oil. Residual traces of citric acid or phosphoric acid play an important role in stabilizing processed oils. The tocopherol content is also important, although no additional stabilization of the oil occurs on adding levels of tocopherol above those present naturally in the crude oil. A combined phosphoric acid degumming and bleaching process leads to smaller losses of tocopherols than sequential treatments.     

Assessment of thin-film oxidation with ultraviolet irradiation for predicting the oxidative stability of edible oils

The oxidative stability of edible oils and samples of rapeseed oil with added antioxidants, metal ions, phospholipids and oxidized oil was assessed by a method involving oxidation of a thin film of oil with ultraviolet (UV) irradiation at 100°C. Induction times determined by this method were compared with those determined with the Rancimat at 100°C. The two methods agreed well in describing the effects of additives on the stability of the edible oil. Induction times were considerably shorter for the thin-film UV method, and the method may have potential as an accelerated test method for assessing the effect of additives on the oxidative stability of relatively stable oils and fats. The correlation between the Rancimat and the thin-film UV induction times also was assessed at 80°C for rapeseed oil containing additives, but there was no advantage in using the lower temperature alone because the induction times were 2–7 times longer than at 100°C. However, use of two elevated temperatures is likely to improve predictions of stability at lower temperatures, especially for samples containing copper, which have an exceptionally high-temperature coefficient. The thin-film UV method showed a poorer agreement with the Rancimat for comparing the oxidative stability of some fats and oils. For instance, corn oil was more stable than soybean oil in the Rancimat test but the order of stability was reversed in the thin-film UV test. Cocoa butter was much more stable in the Rancimat test than when assessed by the thin-film UV test.     

Rheological prediction of the physical stability of concentrated dispersions containing particulates

A dynamic rheological technique is presented that can be used for the prediction of physical stability of concentrated dispersions containing particulates, as well as product development and quality control. Typical physical evaluation frequently requires weeks or months before an assessment can be made. By using dynamic rheology, the prediction of physical stability can often be accomplished in less than three (3) hours. The dynamic or oscillatory rheology technique is performed in two parts. First, a strain sweep test (frequency constant, strain variable) defines the linear viscoelastic range (LVR). Second, frequency scans (from 0.01 to 5.0 Hz) are performed at various temperatures, from 5 to 49°C (40–120°F). It is critical that the frequency scans are performed in the LVR. Dynamic rheology measurements yield data on the elastic (G′) and viscous (G″) moduli. Plotting the elastic to viscous moduli ratio as a function of frequency and temperature generates a 3-D surface which is a “fingerprint” of the dispersion’s colloidal stability. The G′/G″ ratios correlate well with observed physical stability properties. A volume index or a simple mean/variance calculation can be used to assign a value to the graphical 3-D representations. Presented April, 1990, at the AOCS National Meeting, Baltimore, MD.     

Determination of oxidative stability of lipids in solid samples

A gas-phase flow injection analysis (FIA) method for the direct determination of the oxidative stability of solid fat/oil samples is described. Samples are confined with a low level of oxygen in a reactor of adjustable temperature. The oxygen consumption by the sample is automatically monitored after a preset period. The temperature-dependent data exhibit Arrhenius behavior. Normally, it is difficult to directly determine the stability at ambient temperatures because of inordinately long time requirements. The close correspondence to Arrhenius behavior makes it possible to use the results obtained at higher temperature to calculate the stability of samples at lower temperature conditions, such as at ambient storage temperature. The effects of sample size, sample particle size, sample fat content and the reproducibility of the method over time were studied using synthetic and bone meal samples. The oxygen consumption was found to be linearly dependent on the amount of sample taken, inversely dependent on the particle diameter, and independent of the exact lipid content, given some minimum lipid content. The results exhibited high day-to-day reproducibility. The gasphase FIA system developed in this work is easy to operate. Compared with the currently used method, the sample throughput rate is much faster (2–3h for complete multitemperature characterization of a sample) and the sample requirement is much lower (∼1 g). Furthermore, it eliminates the need to extract and recover the fat from the sample for further processing as is required by the other methods commonly used to measure oxidative stability.     

Spray and freeze drying of human milk on the retention of immunoglobulins (IgA,IgG, IgM)

Several freeze-drying and spray-drying methods were investigated in relation to the retention of immunoglobulins (Ig) A, IgG, and IgM. Spray drying produced human milk powders with 2% humidity and a good retention of IgG (>88%) and IgM (～70%). However, only 38% of IgA remained after spray drying. For freeze drying, only the highest heating plate temperature used in this study (40°C) brought IgA content down to 55% in powder with 1.75% residual humidity, whereas milk samples undergoing lower temperatures had higher preservation rates (75% for IgA and 80% for IgG and IgM) and higher residual moisture contents. From these results, it can be concluded that IgA is the most sensitive Ig lost during drying processing of human milk. The best method to generate human milk powders without a significant loss of Ig was thus freeze drying at 30°C heating plate temperature, which accelerated the process compared to lower processing temperatures, but still had good overall Ig retention.     

Effect of randomization on the oxidative stability of corn oil

Randomized corn oil TAG oxidized much faster than natural oil, but after purification with alumina, they oxidized at the same rate. We showed that this effect could not be attributed to a difference, in total tocopherols in the randomized and natural oils. Polar material recovered from the alumina treatment was fractionated by TLC, and a pro-oxidant effect was found in the fractions containing MAG and DAG. However, MAG and DAG, although mild pro-oxidant could not account for the pro-oxidant effect generated by randomization. No other compounds could be detected in the MAG fraction by MS. The pro-oxidant effect of randomized oil disappeared when EDTA or citric acid was added in sufficient amounts. The pro-oxidant effect of randomized corn oil was increased by the incorporation of additional copper or iron at a concentration that did not catalyze oxidation of the purified oil. Treatment of corn oil with ascorbic acid, ascorbyl-6-palmitate, ethyl acetoacetate, ethyl diacetoacetate, and acetylacetone did not reproduce the effect of the unknown pro-oxidant. Although the identity of the pro-oxidant is still unknown, we have confirmed that it is produced during randomization; it does not have pro-oxidant activity alone, but it facilitates the catalytic activity of the transition metal ions.