Application of compression test in analysis of mechanical and color changes in grapefruit juice powder as related to glass transition and water activity

Physicochemical and structural properties of grapefruit juice powder were studied as affected by water activity. Powdered juice was obtained by freeze-drying and equilibrated at different water vapor pressure atmospheres in order to give samples with water activity in the range of 0-084 The mechanical properties of the powder were measured by confined compression tests and the compressed samples, which presented uniform surface and thickness, were subjected to color analysis The maximum force attained during the compression tests and the color coordinates could be quantified with good reproducibility. The results were related to water activity and to glass transition temperature The occurrence of mechanical changes in the powder was shown to precede significant color changes with increasing water activity. Considering the susceptibility to stickiness, the stability limit was observed at T-T(g) approximate to 2 degrees C, with a high degree of mechanical changes being detected at T-Tg 16 degrees C, whereas for significant color changes this critical temperature difference was around 32 degrees CAuthors thank the Ministerio de Educacion y Ciencia and the Fondo Europeo de Desarrollo Regional (FEDER) for the financial support throughout the projects AGL2002-01793 and AGL 200505994. Vania R. N. Tells acknowledges the support of the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES) as an external grant (Proc. BEX 4452/06-2).Telis, VRN.; Martínez Navarrete, N. (2010). Application of compression test in analysis of mechanical and color changes in grapefruit juice powder as related to glass transition and water activity. Food Science and Technology. 43(5):744-751. https://doi.org/10.1016/j.lwt.2009.12.007S74475143

Optimization of spray-drying conditions for lulo (Solanum quitoense L.) pulp

The spray drying of lulo was optimized by using the central composite design of the response surface methodology, to study the effect of inlet air temperature (120-180 degrees C), arabic gum concentration (0-10% w/w), and maltodextrin DE16.5-19.5 concentration (0-10% w/w) on some product and process aspects. Arabic gum and maltodextrin, more than inlet air temperature, improved the product yield, reduced the hygroscopicity and the water content of the obtained powder, and contributed to the retention of its nutritive and functional properties through an increase in ascorbic acid, vitamin C, total phenol and total flavonoid content and antioxidant capacity. Significant (p < 0.05) response surface models were obtained in every case, with the linear terms of solute concentration being the factors that affected the response variables most significantly. The overall optimum spray drying conditions for obtaining lulo powder were 125 degrees C inlet air temperature, 3% (w/w) arabic gum, and 13.4% (w/w) maltodextrin DE16.5-19.5. (C) 2014 Elsevier B.V. All rights reserved.The authors thank the Universidad Politecnica de Valencia for the financial support given throughout the Project ADSIDEO-COOPERACION 2010 "Adaptacion de procesos de secado para favorecer la comercializacion de super frutas de origen colombiano".Igual Ramo, M.; Ramires, S.; Mosquera, LH.; Martínez Navarrete, N. (2014). Optimization of spray-drying conditions for lulo (Solanum quitoense L.) pulp. Powder Technology. 256:233-238. doi:10.1016/j.powtec.2014.02.003S23323825

Overcoming the caking phenomenon in olive mill wastes

The use of olive mill wastes (orujillo) within coal fired power stations in the UK has led to unexpected difficulties with material caking within the fuel handling plant. This study replicated orujillo caking on a laboratory scale using a planetary ball mill and explored the impact of mill parameters (speed, volume, and duration) on the caking phenomenon. The impact of orujillo composition was examined for 4 sections of fresh and dried orujillo (whole, pulp 0-850 µm, pulp 850-3350 µm, and cluster 3350 µm+) for set milling conditions. Caking was induced by heat generation within the mill and was most prevalent in the pulp section of orujillo. Caking was brought on by a glass transition step, which was measured to be around 97-98 °C for a moisture content of 6-7% in a differential scanning calorimeter (DSC). Caking was the result of the bulk moisture content (14-18%) being higher than the standard moisture content of orujillo (< 12%), and can be mitigated through drying. Thus the key to overcoming orujillo caking in fuel handling plants is through moisture content control. Additionally, as the caking issue is most prevalent in the pulp section, all fines below the required combustion particle size (typically < 1 mm) should be removed prior to comminution and sent directly to the burner. This would also reduce the comminution load by nearly 50%, increase the energy potential of the fuel, and remove the most problematic section of orujillo from the fuel handling plant

Som galna vildhästar eller sniglar med bromsarna på – Skolchefers syn på den kritiska mediekompetens möjligheter och hinder i grundskolans värld

Titel: Som galna vildhästar eller sniglar med bromsarna på – Skolchefers syn på den kritiska mediekompetens möjligheter och hinder i grundskolans värld Författare: Susanna Boonyai Handledare: Annika Bergström Kurs: Medie- och kommunikationsvetenskap, examensarbete Institutionen för journalistik, medier och kommunikation (JMG) Göteborgs universitet Termin: Höstterminen 2009 Syfte: Det övergripande syftet med studien är att utreda möjligheter och hinder för kritisk mediekompetens i grundskolans värld. Metod: Studiens val av metod är den kvalitativa forskarmetoden i form av intervjuer med skolchefer, inom ansvarsområdet förskola och grundskola. Material: Åtta stycken intervjuer med skolchefer fördelade på de ansvarsområden som skolcheferna är verksamma inom. Uppdelningen fördelades jämt mellan resurssvaga, medelresurssvaga, medelresursstarka och resursstarka områden. Huvudsakliga resultat: Skolcheferna har generellt tämligen goda kunskaper om vad kritisk mediekompetens kan anses handla om, framförallt med betoning på att medier skall göras till-gängliga för alla i skolans värld och som är centralt inom diskursen för kritisk mediekompetens. Den djupare kunskapsdimensionen kring kritisk mediekompetens som handlar om att lära sig kritiskt granska all typ av medier finns där men hur väl ett fördjupat resonemang är utvecklat varierar dock inom denna grupp skolchefer vilket tyder på ett behov av ökade kunskaper inom området. Det sker försök till en implementering av kritisk mediekompetens inom de områden som skolcheferna är verksamma på många olika plan. Genom bland annat PIM, ett överstatligt webbaserat utbildningsprogram för kritisk mediekompetens, skall alla pedagoger och rektorer ha uppnått nivå 3 i sin utbildning inom tre år. Pedagoger befinner sig dock på många olika kunskapsnivåer i detta program. Därför pekar mina resultat på att en implementering av kritisk mediekompetens i dagsläget inte är likvärdig eftersom inte alla pedagoger har möjlighet att möta elevernas olika kunskapsnivåer likvärdigt i de områden som skolcheferna är verksamma inom. Skolchefers syn på styrdokumenten är komplexa och ett behov av ett tydliggörande verkar inte vara den väg som skolchefer tycker man skall gå. Samtidigt anser samt-liga skolchefer att det finns stora problem med att styrdokumenten är skrivna på nittiotalet med tanke på den snabba mediala utvecklingen. Därför har skolcheferna höga förväntningar på de nya styrdokument, som är under utveckling. Här hoppas de framförallt på att en tydligare implementering med betoning på ett användarperspektiv skall skrivas in i dokumenten. Parallellt ser också skolchefer hellre att kritisk mediekompetens integreras och utvecklas inom alla ämnen utan ett förtydligande i styrdokumenten. Ett synsätt som på sätt och vis också är förankrat hos förespråkare som vill utveckla kritisk mediekompetens i skolans värld

Stickiness measurement techniques for food powders: a review

The importance of sticky behaviour of amorphous food powders has been recognized over many decades in the food industry due to its influence on process and handling abilities and quality of the powders. This paper emphasizes the role of stickiness in the food powder industry as well as reviews the stickiness characterization techniques developed to date. This paper also attempts to correlate the stickiness behaviour of food powders to the instrumental analysis such as glass transition temperature. (C) 2004 Elsevier B.V All rights reserved

Instrumentation and testing of a thermal mechanical compression test for glass-rubber transition analysis of food powders

A thermally controlled sample cell was developed and attached to a texture analyser for the glass-rubber transition analysis of food powders. The glass-rubber transition temperature was determined from mechanical changes measured during a thermal compression test. A standard procedure for the thermal mechanical compression test (TMCT) has been established. The results obtained from the TMCT technique were validated against standard DSC and TMA methods using skim milk powder as a model food powders. This technique was found valid for the analysis of food powder's glass-rubber transition. Compression forces of 19.62-49.05 N, heating rates of 20-50 degrees C/min and sample quantities of 0.5-1.0 g are recommended for food powder testing. (c) 2006 Elsevier Ltd. All rights reserved

Measurement of glass-rubber transition temperature of skim milk powder by static mechanical test

Stickiness behavior of skim milk powder was investigated based on the mechanical property of the material during the glass-rubber transition. A thermally controlled device was developed for the static mechanical test. This device was attached to a texture analyzer, and skim milk powder, which was used as a model sample, was tested for its glass-rubber transition temperature (Tg-r) using static compression technique (creep test). Changes in compression probe distance as a function of temperature were recorded. Tg-r was determined, in the region where changes in the probe distance were observed, by using linear regression technique. The effect of sample quantity, compression force, and heating rate on the determination of Tg-r was investigated. All these parameters significantly influenced the Tg-r determination (p < 0.05). The Tg-r of skim milk powder measured by this novel technique was found closely correlated to its glass transition temperature (T-g) measured by DSC