Compositional and textural properties of milkfat-soybean oil enzymatic interesterification

Milkfat-soybean oil blends were enzymatically interesterified (EIE) by Aspergillus niger lipase immobilized on SiO(2)-PVA hybrid composite in a solvent free system. An experimental mixture design was used to study the effects of binary blends of milkfat-soybean oil (MF:SBO) at different proportions (0:100; 25:75; 33:67; 50:50; 67:33; 75:25; 100:0) on the compositional and textural properties of the EIE products, considering, as response variables, the interesterification yield (IY), consistency and hardness. Lipase-catalysed interesterification reactions increased the relative proportion of TAGs` C(46)-C(52) and decreased the TAGs` C(40)-C(42) and C(54) concentrations. The highest IY was attained (10.8%) for EIE blend of MF:SBO 67:33 resulting in a more spreadable material at refrigerator temperature in comparison with butter, milkfat or non-interesterified (NIE) blend. In this case, consistency and hardness values were at least 32% lower than values measured for butter. Thus, using A. niger lipase immobilized on SiO(2)-PVA improves the textural properties of milkfat and has potential for development of a product incorporating unsaturated and essential fatty acids from soybean oil. (C) 2010 Elsevier Ltd. All rights reserved.

Effect of huitlacoche (Ustilago maydis DC Corda) paste addition on functional, chemical and textural properties of tortilla chips

AbstractThis study analyzed the addition of huitlacoche paste (HP) in baked tortilla chips (TC), evaluating its effects on functional, physicochemical and structural changes during processing. Two blue corn grains were nixtamalized, stone milled, air dried and milled to obtain flour; commercial blue corn flour (TM1) and commercial TC (TM2) were used as controls. Additions of 0, 3, 6 and 9% of HP were formulated; masas were prepared at 55% moisture content (MC), precooked and baked in an industrial machine. TC crispiness was influenced by grain characteristics and percentage of HP. Huitlacoche paste addition caused an increase in total dietary fiber (from 5.27 to 14.54%), total soluble phenolics content (from 17.52 to 37.60 mg GAE/100 g) and antioxidant capacity (from 6.74 to 7.98 μmol TE/g) in TC. Results suggest that tortilla chips added with huitlacoche can be an alternative to prepare this traditional edible fungus and produce healthier snacks, not fried and enriched with bioactive compounds.

Effects of combined high-pressure and heat treatment on the textural properties of soya gels

sSPI, 7S, and 11S globulin at 12% (w/v) protein concentration, at neutral pH, did not form gels when heat-treated (90 degreesC, 15 min) or when high pressure-treated (300-700 MPa), except for the I IS, which formed a gel when heat-treated. The combination of heat and pressure (that is heating the solutions in a water bath and then pressure-treating at room temperature or the reverse sequence), led to differences: when heat-treatment was before high-pressure treatment, only the I IS fraction formed a self-standing gel; however, when the solutions were pressurised before heat treatment, all the proteins formed self-standing gels. The textural and water-holding properties were measured on the gels formed with the three different soy proteins. (C) 2002 Elsevier Science Ltd. All rights reserved.

Effect of high hydrostatic pressure processing on rheological and textural properties of probiotic low-fat yogurt fermented by different starter cultures

The effect of milk processing on rheological and textural properties of probiotic low-fat yogurt (fermented by two different starter cultures) was studied. Skim milk fortified with skim milk powder was subjected to three treatments: (1) thermal treatment at 85C for 30 min; (2) high hydrostatic pressure (HHP) at 676 MPa for 5 min; and (3) combined treatments of HHP (676 MPa for 5 min) and heat (85C for 30 min). The processed milk was fermented using two different starter cultures containing Streptococcus thermophilus, Lactobacillus delbrueckii ssp. bulgaricus, Lactobacillus acidophilus and Bifidobacterium longum at inoculation rates of 0.1 and 0.2%. Rheological parameters were determined and a texture profile analysis was carried out. Yogurts presented different rheological behaviors according to the treatment used, which could be attributed to structural phenomena. The combined HHP and heat treatment of milks resulted in yogurt gels with higher consistency index values than gels obtained from thermally treated milk. The type of starter culture and inoculation rate, providing different fermentation pathways, also affected the consistency index and textural properties significantly. The combined HHP and heat treatment of milks before fermentation, and an inoculation rate of 0.1% (for both cultures), led to desirable rheological and textural properties in yogurt, which presented a creamy and thick consistency that does not require the addition of stabilizers.

Post-combustion CO2 adsorption on activated carbons with different textural properties

Fixed bed CO2 adsorption tests were carried out in model flue-gas streams onto two commercial activated carbons, namely Filtrasorb 400 and Nuchar RGC30, at 303 K, 323 K and 353 K. Thermodynamic adsorption results highlighted that the presence of a narrower micropore size distribution with a prevailing contribution of very small pore diameters, observed for Filtrasorb 400, is a key factor in determining a higher CO2 capture capacity, mostly at low temperature. These experimental evidences were also corroborated by the higher value of the isosteric heat derived for Filtrasorb 400, testifying stronger interactions with CO2 molecules with respect to Nuchar RGC30. Dynamic adsorption results on the investigated sorbents highlighted the important role played by both a greater contribution of mesopores and the presence of wider micropores for Nuchar RGC30 in establishing faster capture kinetics with respect to Filtrasorb 400, in particular at 303 K. Furthermore, the modeling analysis of 15% CO2 breakthrough curves allowed identifying intraparticle diffusion as the rate-determining step of the process.

Assessment of high hydrostatic pressure and starter culture on the quality properties of low-acid fermented sausages

The addition of starter culture and high pressure processing after ripening improved the microbial quality of low-acid fermented sausages (fuet and chorizo). The use of Lactobacillus sakei CTC6626 and Staphylococcus xylosus CTC6013 as starter culture significantly reduced Enterobacteriaceae and Enterococcus levels in the finished sausages. Moreover, the addition of starter culture produced sausages of similar quality to traditional low-acid fermented sausages. Slightly lower pH values and higher cohesiveness were obtained for both fuet and chorizo with starter culture. Sensory analysis showed no differences between lots of chorizo whereas starter fuet was more acid and gummy. High pressure induced an additional reduction of Enterobacteriaceae in non-starter sausages. An increase of textural properties was observed after pressurization. No other differences were observed between non-treated and pressurized sausages.

Properties of silica from rice husk and rice husk ash and their utilization for zeolite y synthesis

This study compared properties of silica (SiO2) from rice husk (RH) and rice husk ash (RHA) extracted by acid- and heat-treatment. The SiO2 from RH was in amorphous phase with nearly 100% purity while that from RHA was in crystalline phase with 97.56% purity. Both extracted SiO2 were used in the synthesis of zeolite NaY but that from RH was better due to the efficiency in product recovery and simplicity of extraction. After the NaY was exchanged to NH4Y and calcined to convert to HY, the product did not carry over the textural properties of the parent NaY and NH4Y.

Effects of milk supplementation with skim milk powder, whey protein concentrate and sodium caseinate on acidification kinetics, rheological properties and structure of nonfat stirred yogurt

Milk supplementation with milk proteins in four different levels was used to investigate the effect on acidification and textural properties of yogurt. Commercial skim milk powder was diluted in distilled water, and the supplements were added to give different enriched-milk bases; these were heat treated at 90 degrees C for 5 min. These mixtures were incubated with the bacterial cultures for fermentation in a water bath, at 42 degrees C, until pH 4.50 was reached. Chemical changes during fermentation were followed by measuring the pH. Protein concentration measurements, microbial counts of Lactobacillus bulgaricus and Streptococcus thermophilus, and textural properties (G`, G ``, yield stress and firmness) were determined after 24 h of storage at 4 degrees C. Yogurt made with milk supplemented with sodium caseinate resulted in significant properties changes, which were decrease in fermentation time, and increase in yield stress, storage modulus, and firmness, with increases in supplement level. Microstructure also differed from that of yogurt produced with milk supplemented with skim milk powder or sodium caseinate. (C) 2009 Elsevier Ltd. All rights reserved.

Optimization of the rheological properties of probiotic yoghurts supplemented with milk proteins

This study aimed to optimize the rheological properties of probiotic yoghurts supplemented with skimmed milk powder (SMP) whey protein concentrate (WPC) and sodium caseinate (Na-Cn) by using an experimental design type simplex-centroid for mixture modeling It Included seven batches/trials three were supplemented with each type of the dairy protein used three corresponding to the binary mixtures and one to the ternary one in order to increase protein concentration in 1 g 100 g(-1) of final product A control experiment was prepared without supplementing the milk base Processed milk bases were fermented at 42 C until pH 4 5 by using a starter culture blend that consisted of Streptococcus thermophilus Lactobacillus delbrueckii subsp bulgaricus and Bifidobacterium (Humans subsp lactis The kinetics of acidification was followed during the fermentation period as well the physico-chemical analyses enumeration of viable bacteria and theological characteristics of the yoghurts Models were adjusted to the results (kinetic responses counts of viable bacteria and theological parameters) through three regression models (linear quadratic and cubic special) applied to mixtures The results showed that the addition of milk proteins affected slightly acidification profile and counts of S thermophilus and B animal`s subsp lactis but it was significant for L delbrueckii subsp bulgaricus Partially-replacing SMP (45 g/100 g) with WPC or Na-Cn simultaneously enhanced the theological properties of probiotic yoghurts taking into account the kinetics of acidification and enumeration of viable bacteria (C) 2010 Elsevier Ltd All rights reserved

Analysis of factors influencing the physical, chemical and sensorial properties of Serra da Estrela cheeses

The objective of this study was to evaluate the chemical, color, textural, and sensorial characteristics of Serra da Estrela cheese and also to identity the factors affecting these properties, namely thistle ecotype, place of production, dairy and maturation. The results demon- strated that the cheeses lost weight mostly during the first stage of maturation, which was negatively correlated with moisture content, being this also observed for fat and protein contents. During maturation the cheeses became darker and with a yellowish coloration. A strong corre- lation was found between ash and chlorides contents, being the last directly related to the added salt in the manufacturing process. The flesh firmness showed a strong positive correlation with the rind harness and the firmness of inner paste. Stickiness was strongly related with all the other textural properties being indicative of the creamy nature of the paste. Adhesiveness was posi- tively correlated with moisture content and negatively correlated with maturation time. The trained panelists liked the cheeses, giving high overall assessment scores, but these were not significantly correlated with the physicochemical properties. The salt differences between cheeses were not evident for the panelists, which was corroborated by the absence of correlation between the perception of saltiness and the analyzed chlorides con- tents. The Factorial Analysis of the chemical and physical properties evidenced that they could be explained by two factors, one associated to the texture and the color and the other associated with the chemical properties. Finally, there was a clear influence of the thistle ecotype, place of production and dairy factors in the analyzed properties.

Templated synthesis of carbon materials mediated by porous clay heterostructures

Mesoporous carbon materials were prepared through template method approach using porous clay heterostructures (PCHs) as matrix and furfuryl alcohol as carbon precursor. Three PCHs prepared using amines with 8, 10 and 12 carbon atoms were used. The effect of several impregnation-polymerization cycles of the carbon precursor, the carbonization temperature and the need of a previous surface alumination were evaluated. The presence of two porosity domains was identified in all the carbon materials. These two domains comprise pores resulting from the carbonization of the polymer film formed in the inner structure of the PCH (domain I) and larger pores created by the clay particles aggregation (domain II). The predominance of the porosity associated to domain I or II can be achieved by choosing a specific amine to prepare the PCH matrix. Carbonization at 700 C led to the highest development of pores of domain I. In general, the second impregnation-polymerization cycle of furfuryl alcohol resulted in a small decrease of both types of porosity domains. Furthermore the previous acidification of the surface to create acidic sites proved to be unnecessary. The results showed the potential of PCHs as matrices to tailor the textural properties of carbons prepared by template mediated synthesis.

Avaliação do desempenho de adsorventes obtidos a partir de resíduos da indústria de curtumes na adsorção de poluentes

Na procura por uma solução de valorização dos resíduos gerados pela indústria de curtumes, o presente trabalho tem como principais objectivos a preparação de adsorventes a partir de resíduos desta actividade e a avaliação do seu desempenho na adsorção de poluentes. Para atingir este objectivo, inicialmente procedeu-se à carbonização das aparas de couro wet-white à temperatura de 800 ºC. Seguidamente, os carbonizados foram activados por activação química, tendo sido o hidróxido de potássio o agente activante escolhido. As razões mássicas hidróxido de potássio:precursor usadas na impregnação, foram iguais a 0,5:1 e 1:1. Para a razão 0,5:1, as temperaturas de activação escolhidas foram 700 e 800 ºC. Para a razão de impregnação 1:1, as temperaturas de activação usadas foram 700, 800 e 900 ºC. Para uma avaliação preliminar da capacidade de adsorção dos carvões activados produzidos, efectuou-se a determinação do número de azul de metileno. Este teste provou serem as amostras activadas a 900 ºC as que apresentaram melhores resultados (número de azul de metileno: 24g/100g) e as amostras activadas a 700 ºC, as que apresentaram menor capacidade de adsorção (1g/100g, para a razão de 0,5:1 e 7g/100g, para a razão de 1:1). Verificou-se também que amostras preparadas com iguais condições de activação (temperatura de activação e razão de impregnação), mas produzidas a partir de carbonizado de diferentes granulometrias, apresentaram diferentes desempenhos na adsorção de azul de metileno. As propriedades texturais dos carvões activados produzidos foram obtidas pela determinação das isotérmicas de adsorção de azoto a 77 K. Para tal, selecionaram-se quatro amostras: dois carvões activados a 800 ºC, com uma razão de impregnação de 1:1 e dois carvões activados a 900 ºC, com a mesma razão de impregnação, obtidos a partir de carbonizados com diferentes granulometrias. As isotérmicas obtidas são características de materiais essencialmente microporosos, com mesoporos e macroporos. Verificou-se também que a granulometria do precursor carbonizado influencia as propriedades texturais dos carvões activados produzidos. Para as temperaturas de activação usadas, 800 e 900 ºC, os carvões activados preparados a partir de carbonizado de menor granulometria apresentam melhores propriedades texturais. O carvão activado que apresentou maior área superficial específica foi obtido a 900 ºC, a partir de carbonizado finamente moído (SBET = 1475 m2/g). Determinadas as propriedades texturais dos carvões activados produzidos, realizaram-se ensaios de adsorção do corante CORIACIDE DARK BROWN VR, usado na indústria de curtumes com um carvão activado produzido no âmbito deste trabalho e com um carvão activado comercial NORIT ROW 0,8. A amostra de carvão activado produzida a partir de resíduos de wet-white escolhida para estes ensaios foi o carvão activado a 800 ºC, à razão de 1:1, a partir de carbonizado finamente moído (ww_800_1:1_carb.moído). Verificou-se que as quantidades adsorvidas pela amostra ww_800_1:1_carb.moído variaram entre os valores 7,47 e 32,07 mgcorante/gcarvão activado. Quanto ao carvão activado comercial, as quantidades adsorvidas situaram-se entre 8,95 e 69,13 mgcorante/gcarvão activado. Assim, conclui-se que o carvão activado comercial apresentou melhor desempenho na adsorção do corante da indústria de curtumes. Os carvões activados obtidos revelaram-se materiais essencialmente microporosos, com capacidade de adsorção de poluentes, como por exemplo corantes, no entanto o seu desempenho seria mais eficaz na adsorção de pequenas moléculas devido ao elevado volume de microporos que apresentaram.

Produção de carvão activado a partir de resíduos da indústria de curtumes

As aparas de wet-blue e de wet-white constituem um resíduo sólido da indústria de curtumes com um elevado teor em carbono, tornando relevante a sua utilização na preparação de materiais de interesse tecnológico. Este trabalho teve como objectivo a preparação de carvões activados a partir de resíduos da indústria de curtumes. Os métodos de activação utilizados para a preparação dos carvões activados foram a activação física com dióxido de carbono e activação química com hidróxido de potássio. A carbonização dos resíduos foi estudada na gama de temperaturas de 500 ºC a 800 ºC, verificando-se que a sua carbonização se pode considerar completa para a temperatura de 800 ºC. Na activação física os precursores foram previamente carbonizados sob uma atmosfera inerte a 800 ºC e posteriormente activados a 940 ºC usando o CO2 como agente activante. Na etapa de activação variou-se o tempo de activação (20, 40 e 60 minutos) de modo a estudar a influência do grau de queima nas propriedades texturais dos carvões activados. O carvão activado obtido pelo método de activação física com maior área superficial específica foi o carvão preparado a partir do resíduo de wet-blue para um tempo de activação de 40 minutos e grau de queima de 23 % (SBET = 152 m2/g). Para a activação química, procedeu-se à impregnação dos precursores com KOH usando razões mássicas de impregnação KOH:precursor de 0,5:1, 1:1 e 3:1. A impregnação foi efectuada directamente nos resíduos de wet-blue e de wet-white e nos resíduos de wet-blue e de wet-white carbonizados. A activação foi efectuada a 940 ºC sob uma atmosfera inerte, com uma velocidade de aquecimento de 5 ºC/min, e um tempo de activação de 1 hora. No caso da série de carvões activados obtidos por impregnação do precursor, o carvão que exibe melhores propriedades texturais é o carvão activado preparado por impregnação na razão de 1:1 a partir do resíduo de wet-blue (SBET = 1696 m2/g). Na série de carvões activados preparados por impregnação do precursor carbonizado, o carvão com melhores propriedades texturais é o carvão proveniente da impregnação do carbonizado do resíduo de wet-blue na razão de 3:1 (SBET = 1507 m2/g). Os carvões activados obtidos por este método de activação são essencialmente microporosos e com elevada área superficial específica. Testes de adsorção preliminares mostram que estes carvões activados têm um bom desempenho para a remoção de cor de efluentes da indústria de curtumes. Concluiu-se que por activação química com KOH dos resíduos de wet-blue e wet-white se obtêm carvões activados com boas propriedades texturais, elevadas áreas superficiais específicas e elevado volume de microporos, quando comparadas com as dos carvões activados resultantes da activação física. Deste modo, chegou-se à conclusão que ambos os resíduos são bons precursores para a produção de carvão activado, mais propriamente recorrendo à activação química, reduzindo assim o volume de resíduos da indústria de curtumes destinados ao aterro.

Preparação de materiais de carbono para a adsorção de compostos orgânicos voláteis (COV).

A presente dissertação estudou a produção de carvão ativado a partir de resíduo de wet-blue, proveniente da indústria de curtumes, para a adsorção de compostos orgânicos voláteis, nomeadamente o acetato de etilo. Este estudo teve como principais objetivos: a otimização das condições de preparação de carvões ativados a partir deste tipo de resíduo; a avaliação do seu desempenho na adsorção do acetato de etilo e a correlação das propriedades texturais dos adsorventes com o seu desempenho na adsorção do COV. O método de ativação para a preparação dos carvões ativados foi a ativação química com hidróxido de potássio. Nesta etapa foi estudado o efeito da temperatura de ativação e da razão de impregnação KOH:precursor nas propriedades texturais. Nestes ensaios observou-se uma diminuição do rendimento de carbonizado com o aumento da temperatura de ativação e da razão KOH:precursor. Para a caracterização dos carvões ativados foram determinados os seus parâmetros texturais a partir das isotérmicas de adsorção/dessorção de N2 a 77 K. O carvão ativado com melhores propriedades texturais foi o ativado a 900ºC e com razão de impregnação de 3:1, m ca_900 3:1, com área superficial específica de 1902 m2/g, seguindo-se o carvão preparado a 800 ºC e com a mesma razão de impregnação, m ca_800 3:1, com área superficial específica de 1830 m2/g. Por fim, foi avaliado o desempenho do carvão ativado selecionado, m ca_800 3:1, na remoção de acetato de etilo de uma corrente gasosa. Foram efetuados ensaios de adsorção/ dessorção de acetato de etilo e o modelo de Langmuir foi ajustado aos resultados experimentais obtidos, tendo-se determinado uma capacidade de saturação de 500 mgCOV/ gadsorvente.

Ação promotora do berílio em catalisadores da síntese do estireno

The catalytic dehydrogenation of ethylbenzene in presence of steam is the main commercial route to produce styrene. The industrial catalysts are potassium- and chromia-doped hematite which show low surface areas leading to bad performance and short life. In order to develop catalysts with high areas, the effect of beryllium on the textural properties and on the catalytic performance of this iron oxide was studied. The influence of the amount of the dopant, the starting material and the calcination temperature were also studied. In sample preparations, iron and beryllium salts (nitrate or sulfate) were hydrolyzed with ammonia and then calcinated. The experiments followed a factorial design with two variables in two levels (Fe/Be= 3 and 7; calcination temperature= 500 and 700ºC). Solids without any dopant were also prepared. Samples were characterized by elemental analysis, infrared spectroscopy, surface area and porosity measurements, X-ray diffraction, DSC and TG. The catalysts were tested in a microreactor at 524ºC and 1 atm, by using a mole ratio of steam/ ethylbenzene=10. The selectivity was measured by monitoring styrene, benzene and toluene formation. It was found that the effect of beryllium on the characteristics of hematite and on its catalytic performance depends on the starting material and on the amount of dopant. Surface areas increased due to the dopant as well as the nature of the precursor; samples produced by beryllium sulfate showed higher areas. Beryllium-doped solids showed a higher catalytic activity when compared to pure hematite, but no significant influence of the anion of starting material was noted. It can be concluded that beryllium acts as both textural and structural promoter. Samples with Fe/Be= 3, heated at 500ºC, lead to the highest conversion and were the most selective. However, catalysts prepared from beryllium sulfate are the most promising to ethylbenzene dehydrogenation due to their high surface area which could lead to a longer life.