Avaliação do efeito das variáveis de processo na produção de malte de cevada e na produção de bebidas tipo chá

Abstract

Resumo: O processo de maltagem consiste na hidratacao, germinacao e secagem do produto final. O objetivo e produzir malte com altos teores de acucares e baixos teores de ƒÀ-glucana. Os dois primeiros capitulos dessa tese tiveram o objetivo de mapear o processo de hidratacao da cevada atraves de isotermas de absorcao de agua, modelagem, avaliacao das enzimas do processo de maltagem e do produto final (malte). O terceiro capitulo avaliou o uso da cevada torrada para producao de bebidas tipo cha. Capitulo 1 A cinetica de hidratacao de seis cultivares de cevada foi descrita atraves dos modelos de Peleg, Weibull e Cinetico de 1‹ ordem, tambem observou-se a incorporacao de agua, densidade, volume e a perda de solidos durante o processo. Estimou-se a energia de ativacao (Ea), entalpia (ƒ¢H*), entropia (ƒ¢S*) e energia de Gibbs (ƒ¢G*). A temperatura apresentou efeito significante (p . 0,05) na hidratacao. As isotermas de hidratacao revelaram duas fases, a primeira fase com alta velocidade de hidratacao, e a segunda fase em que o teor de umidade aumenta lentamente ate atingir a umidade de equilibrio. As constantes de Peleg K1 e K2 diminuiram com o aumento da temperatura. Os coeficientes difusao efetivos variaram de 5,14 a 10,8 X 10-12 m2/s. O modelo de Peleg e o cinetico de 1‹ ordem foram os que melhores descreveram as caracteristicas de absorcao de agua nas temperaturas investigadas. Os cultivares BRS CAUE, BRS BRAU e BRS 195 apresentaram menores valores de Ea o que corresponde a maior taxa de absorcao de agua. Os valores de ƒ¢H* e ƒ¢S* apresentaram valores negativos e houve aumento do ƒ¢G* com o aumento da temperatura confirmando o efeito da temperatura na hidratacao. Utilizando o software COMSOL foi avaliado um modelo para descrever a transferencia de calor e de massa durante o processo observou-se que para se obter graos com 40% de umidade media, foram necessarias 12, 13, 23 e 32 horas para 25, 20, 15 e 10‹C, respectivamente. Capitulo 2 Durante o processo de maltagem os niveis de ƒÀ-glucana diminuiram com o aumento da temperatura e tempo de hidratacao, os teores de ƒ¿ e ƒÀ-amilase aumentaram e foram da ordem de 5,37 a 1,50 e 1,44 a 3,52 respectivamente, e a velocidade media de degradacao foi de 0,012 e 0,006 Units/h respectivamente. Nas analises de indice de absorcao de agua, e proteinas houve diferenca significativa entre as amostras. O indice de solubilidade aumentou de acordo com o tempo e a temperatura de hidratacao. As amostras com hidratacao a 10‹C por 24 horas e 20‹C por 12 horas apresentaram maiores valores de acucares totais que as demais amostras. Na analise de componentes principais observou-se que as amostras 20‹C 12h e 10‹C 24 h sao as mais correlacionadas com os atributos de acucares, ƒÀ-glucana, ƒÀ-amilase e ƒ¿-amilase. Podendo-se concluir que a temperatura de 20‹C por 12 horas e 10‹C durante 24 horas sao os melhores tratamentos para produzir o malte. Capitulo 3 Apos o processo de torra os graos foram moidos e peneirados, o po que reteve na peneira de 425 mm foi o utilizado nas analises. Apos o processo de torra o teor de proteina aumentou de 10,56 para 12,88 g/100g em media, o teor de acucares diminuiu e os compostos fenolicos tiveram aumento nos seus valores de 105,33 para 253,07 ƒÊg de acido ferulico/mL da amostra sem torra para a torrada a 240‹C respectivamente e a atividade antioxidante diminui com o aumento da temperatura de torra de 11,60 para 5,30 ug de DPPH/mL. Na producao de bebidas tipo cha quanto maior a temperatura de torra maior e a liberacao de solidos soluveis na agua. Palavras-chave: isoterma de hidratacao, temperatura e tempo, difusao, modelagem, malte, enzimas, torra, reidratacao.

Abstract: The malting process is the hydration, drying and germination of the final product. The objective is to produce malt with high sugar content and low ƒÀ-glucan content. The first two chapters of this thesis aimed to map and model the hydration of barley by water absorption isotherms, as well as to evaluate the enzymes regarding to the malting process and to the final product (malt). The third chapter analyzed the use of roasted barley for the production of beverages like tea. Chapter 1 The hydration kinetics of six cultivars of barley was described through the models of Peleg, Weibull and first order kinetics also observed incorporation of water, density, volume and loss of solids during the process. The activation energy (Ea), enthalpy (ƒ¢H*), entropy (ƒ¢S*) and Gibbs energy (ƒ¢G*) were estimated. Temperature had a significant effect (p . 0.05) in the hydration of all cultivars. The hydration isotherms reveled were divided into two phases: the first one is characterized by a high water absorption rate, while during the second one the moisture content increases slowly until it reaches the equilibrium moisture content. The Peleg constants K1 and K2 decreased with the temperature rise. The effective diffusion coefficients ranged from 5.14 to 10.8~10-12 m2/s. The models of Peleg and first order kinetics better described the water absorption characteristics at the temperatures investigated compared to Weibull. The cultivars BRS CAUE, BRS BRAU and BRS 195 showed lower Ea which corresponds to a higher water absorption rate. The ƒ¢H* and ƒ¢S* presented negative values and ƒ¢G* increased with the temperature rise, confirming the positive effect of temperature on hydration. Using COMSOL software was evaluated a model to describe heat and mass transfer during the process it was noted that to obtain grains having average humidity of 40%, 12 were necessary, 13, 23 or 32 hours at 25, 20, 15, 10‹C, respectively. Chapter 2 During the malting process the levels of ƒÀ-glucan reduced with the increase of temperature and hydration time. The levels of ƒÀ and ƒ¿-amylase ranged from approximately 5.37 to 1.50 and 1.44 to 3.52, respectively, and the average degradation rate was 0.012 and 0.006 units/h, respectively. Significant differences between samples were observed for the water absorption rate and the protein content. The solubility rate increased with hydration time and temperature. The samples submitted to the processes conducted under 10‹C for 24 hours and 20‹C for 12 hours had higher total sugars content than the other samples. The principal component analysis allowed to conclude that the samples hydrated under the conditions of 20‹C for 12h and 10‹C for 24 h are the most correlated with the contents of sugars, ƒÀ-glucan, ƒÀ-and ƒ¿-amylase. Therefore, these treatments are the best choices to produce malt. Chapter 3 After roasting, the grains were ground and sieved. The dust retained in the 425 mm sieve was used in the analyzes. When barley was roasted at 240‹C, the average protein content increased from 10.56 to 12.88 g/100g, the sugar content decreased and the phenolics increased from 105.33 to 253.07 mg of ferulic acid/mL. Due to the roasting temperature rise, the antioxidant activity decreased from 11.60 to 5.30 ug DPPH/mL. During the production of beverages like tea, the higher the roasting temperature the greater the release of soluble solids in water. Keywords: hydration isotherm, temperature, time, diffusion, modeling, malt, enzymes, roasting, rehydration.