Mathematical Modeling of Withering Characteristics of Tea Leaves

Abstract

The withering characteristics of tea leaves were examined for different temperatures. Tea leaves were withered at a temperature range of 20-45 C with a constant air velocity of 1.1 m/s. The experimental results illustrated the absence of constant-rate drying period and withering took place only in the falling-rate period. During the falling-rate period, at constant drying air flow rate, the drying rate increased and drying time decreased with the increase in drying air temperature. Drying models of Henderson and Pabis and Page were evaluated based on mean bias error (E MB ), root mean square error (E RMS ), correlation coefficient (R 2 ), and the chi square (v 2 ). The Henderson and Pabis model was found to be a better model for describing the withering characteristics of tea leaves for each of the temperatures of 20, 25, 30, and 35 C. The values obtained from Page model were found to be more reasonable for temperatures of 40 and 45 C than the other model. Both the models closely fitted the withering data within a certain range of temperature. The Henderson and Pabis model gave better prediction and satisfactorily described the withering characteristics of tea leaves at temperatures lower than 40 C whereas the Page model fitted well at temperatures greater than 40 C.

Effect of blanching on thin layer drying kinetics of aonla (Emblica officinalis) shreds

“…The constant rate drying period was not observed owing to very high initial water content and drying took place in the falling rate period. This result was in agreement with previous studies on drying of foods (Akpinar et al 2004;Ghodake et al 2006;Singh et al 2006;Kaya et al 2007;Sobukola et al 2007). It showed that diffusion was the most likely physical mechanism governing moisture movement in aonla shreds.…”

A Review of Withering in the Processing of Black Tea

“…Withering is one of the processed requiring the most space . The freshly harvested leaves are conditioned physically and chemically for the next operation (maceration or rolling) (Ghodake et al, 2006). During this period, the shoots partially loose moisture with moisture levels dropping from approximately 70-80% to 60-70% (wet basis), and the turgid shoots become flaccid.…”

CONTRIBUCION AL ESTUDIO DE LA INTENSIFICACION DEL PROCESO DE SECADO DE TOMILLO (Thymus Vulgaris L.): APLICACIÓN DE ULTRASONIDOS DE POTENCIA Y SECADO INTERMITENTE

“…Entre las diferentes investigaciones se puede destacar: Ozcan et al, (2005); Roberts et al, (2008); Ghodake et al, (2006); Karathanos (1999); Xanthopoulos et al, (2007); Wang et al, (2007) …”

“…Rocha (2012) utilizó diferentes modelos empíricos para estudiar la cinética del secado de tomillo a temperaturas de 30, 40, 50, 60 y 70 ºC a una velocidad de 1 m/s. Para el cálculo de la difusividad efectiva uso un modelo de lámina infinita en una hoja obteniendo valores entre 3.69 x 10 -12 y 1.19 x 10 -10 m Existen otras investigaciones sobre la modelación matemática y sobre el estudio de las cinéticas de secado para diversas hortalizas y plantas medicinales, como la albahaca (Ozcan et al 2005), plantas aromáticas , hojas de acelga (Alibas 2006), hojas de té (Ghodake et al 2006), Rehmannia (Rhim et al, 2007), hojas de romero , cebolla (Lee & Kim 2008) y Berberis (Aghbashlo et al 2009). …”

“…These models can be categorized as theoretical, semi-theoretical and empirical (McMinn, 2006;Ozdemir and Devres, 1999). A great deal of research has been carried out into the mathematical modeling and experimental drying processes of different agro-based products, such as kiwifruits (Maskan, 2001), red pepper (Akpinar et al, 2003), aromatic plants , tea leaves (Ghodake et al, 2006), rosemary leaves , onion (Lee and Kim, 2008), and spinach leaves (Doymaz, 2009). …”