Flowability characterization of nanopowders

The applications of nanopowders are increasing significantly over the last years. In most of these applications, the flow behavior of the nanopowders seems to be a complicated, multiparametric but critical issue for the proper design of the processes. We have investigated, classified and compared several different metal oxide nanoparticles with respect to their flow properties. The flow properties of titania, silica and alumina hydrophilic nanopowders as well as their corresponding hydrophobic counterparts were determined by means of an annular shear cell powder flow tester (PFT). All the tested powders showed difficulties in flow while the titania nanopowders showed the highest difficulty among them. The results acquired regarding the compressibility, the flow functions and the effective angle of internal friction revealed that in all the cases the hydrophobic nanopowder seemed to be more cohesive than its hydrophilic counterpart. Moreover, the nanoparticles, no matter their polarity, showed negligible hygroscopicity while in the case of the alumina nanopowders the flow properties can be significantly influenced by ca. 1% (w/w) of moisture content

FREEZEWAVE – Investigation of dielectric properties of food matrices for modelling of microwave assisted freezing

FREEZEWAVE project proposes a highly innovative technique which showed that a small amount of emitted microwave energy combined to a slow freezing rate is able to refine ice crystal size in frozen meat (Xanthakis et al., 2014). FREEZEWAVE project aims at expanding & optimizing the concept to several foods and also at designing industrial equipment. Herein, the structure and the directions of the project as well as the initial results of this study and the preliminary results of the previous study will be illustrated. More specifically, the results regarding the dielectric properties investigation for meat, fish, emulsions and vegetables will be presented. The acquired data will be used for the modelling and numerical simulations of the underlying heat transfer phenomena during the microwave assisted freezing of the aforementioned food matrices

COLDμWAVE ‐ Investigation of microwave blanching of vegetables

COLDμWAVE aims to the development of an innovative environmentally sustainable process for blanching and freezing vegetables with improved textural and nutritional quality. The study which will be carried out will involve the use of microwave electromagnetic irradiation (MW) for blanching and freezing of vegetables. COLDμWAVE will develop tailored equipment for MW blanching of vegetables that has very high energy efficiency and no water consumption. Furthermore, this project will develop innovative pathways in freezing to improve the quality of frozen vegetables by exploring, in a new context, previous results acquired by Xanthakis et al., 2014. The developed process will lead to improved quality characteristics compared to the conventional freezing. Herein, The developed microwave blanching methodology will be presented. Moreover, heat transfer phenomena and energy demands of our microwave blanching approach will be evaluated based on measurements and computer modelling

Influence of water activity on flow properties of constituent powders in spice mixes

A common industrial problem with powders is their failure to discharge reliably from bins, silos and hoppers as well as their insufficient or unpredictable flow in feeders, dosing and packing machines. These problems occur due to the powder’s flow behaviour and often cause adverse interruptions in the production processes. Moreover, different flow properties of constituent powders in mixes may cause variations in mixture homogeneity which in turn may lead to pack weight, performance, sensory properties and quality differentiations of the products. The present study is focused on the influence of water activity on the flow properties of several spice powders. The determination of the flow properties were carried out with the use of a Powder Flow Tester from Brookfield Engineering Laboratories Inc. which complies with the test procedure ASTM D6128 using the annular and Jenike shear tests techniques. Flowabilities of the powders were characterized with respect to their flow function which was constructed by plotting the unconfined yield strength versus the major principal consolidation stress. Interesting results regarding the influence of water content on flow behavior of both the constituent spice powders and their mixtures were acquired from this study. By increasing the water content the cohesiveness of some spices increased significantly while on some other spices it did not seem to have any impact. The corresponding mixtures of spices didn’t follow a linear correlation with the ratio content and the flow properties of the constituent powders

Lime Juice Enhances Calcium Bioaccessibility from Yogurt Snacks Formulated with Whey Minerals and Proteins

Yogurt-based snacks originally with a calcium content between 0.10 and 0.17 mmol/g dry matter were enriched with a whey mineral concentrate and whey protein isolate or hydrolysate. Whey mineral concentrate was added to increase the total amount of calcium by 0.030 mmol/g dry matter. Calcium bioaccessibility was determined following an in vitro protocol including oral, gastric, and intestinal digestion, with special focus on the effect of lime juice quantifying calcium concentration and activity. Calcium bioaccessibility, defined as soluble calcium divided by total calcium after intestinal digestion amounted to between 17 and 25% for snacks without lime juice. For snacks with lime juice, the bioaccessibility increased to between 24 and 40%, an effect attributed to the presence of citric acid. Citric acid increased the calcium solubility both from whey mineral concentrate and yogurt, and the citrate anion kept supersaturated calcium soluble in the chyme. The binding of calcium in the chyme from snacks with or without lime juice was compared electrochemically, showing that citrate increased the amount of bound calcium but with lower affinity. The results indicated that whey minerals, a waste from cheese production, may be utilized in snacks enhancing calcium bioaccessibility when combined with lime juice

Microwave Assisted Blanching and Novel Freezing Methods of Fruits

Fruits and vegetables are mainly seasonal and they are characterized as perishable food matrices due to their short shelf life as several deterioration mechanisms are being involved. Prior to the common preservation methods like freezing or canning, fruits and vegetables are being blanched in order to inhibit subsequent deteriorative enzymatic mechanisms. Both conventional blanching pretreatments and conventional freezing methods hide drawbacks behind their beneficial impacts on the extension of the self-life of those matrices. Conventional blanching methods may require longer processing times, leaching of minerals and nutrients due to the contact with the warm water which in turn leads to effluent production with large BOD. As fruits and vegetables have very sensitive microstructure, an important issue of freezing technologies is the size of the formed ice crystals which is also critical for the final quality of the frozen food as it can cause irreversible damage to the cellular structure and subsequently to degrade the texture and the colour of the product. Herein, the developed microwave blanching methodology and the results regarding enzyme inactivation will be presented. Moreover, heat transfer phenomena, mass balance, temperature distribution, and enzyme inactivation (such as Pectin Methyl Esterase and Ascorbic Acid Oxidase) of our microwave blanching approach will be evaluated based on measurements and computer modelling. The present work is part of the COLDμWAVE project which aims to the development of an innovative environmentally sustainable process for blanching and freezing of fruits and vegetables with improved textural and nutritional quality

FREEZEWAVE – Innovative and low energy microwave assisted freezing process for high quality foods

FREEZEWAVE project proposes a highly innovative technique which showed that a small amount of emitted microwave energy combined to a slow freezing rate is able to refine ice crystal size in frozen meat. FREEZEWAVE project aims at expanding & optimizing the concept to several foods and also at designing industrial equipment. Herein, the structure and the directions of the project as well as the initial results of this study and the preliminary results of the previous study will be illustrated. More specifically, the application of microwaves during cooling the samples caused oscillated decrease of temperature and had a significant impact on the crystallization process as the degree of supercooling was decreased circa 92% under the tested conditions. The meat microstructure evaluation showed a 62% decrease in the average ice crystal size when samples were frozen under a microwave field as compared to the conventional freezing process

Evaluation of dry blanching and microwave assisted freezing of fruits

Prior to the common preservation methods like freezing or canning, fruits and vegetables are being blanched in order to inactivate deteriorative enzymes. Both conventional blanching pre-treatments and conventional freezing methods hide drawbacks behind their beneficial impacts on the preservation of those matrices. Conventional blanching methods may require longer processing times, leaching of minerals and nutrients due to the contact with the warm water which in turn leads to effluent production with large BOD. An important issue of freezing technologies is the size of the formed ice crystals which is also critical for the final quality of the frozen food as it can cause irreversible damage to the cellular structure and subsequently to degrade the texture and the colour of the product. Herein, the developed microwave blanching methodology and the results regarding enzyme inactivation will be presented. In this study mango (Mangifera indica L.) was selected as a fruit matrix and three different scenarios were implemented for both High Temperature Short Time and Low temperature Long Time blanching pre-treatments. Moreover, heat transfer phenomena, mass balance, temperature distribution, and enzyme inactivation (such as Pectin Methyl Esterase and Ascorbic Acid Oxidase) of our microwave blanching approach were evaluated based on measurements and computer modelling. The present work is part of the COLDμWAVE project which aims to the development of an innovative environmentally sustainable process for blanching and freezing of fruits and vegetables with improved textural and nutritional quality. The novel concept of Microwave Assisted Freezing as well as the initial results will be presented