The main objectives of this study were to investigate the effect of different temperature of hot air drying on the qualities of dried peppermint, including essential oil content, colour parameters, and visual sensory quality and to develop mathematical models for the colour change kinetics. | Joumal of Science and Technology 54 (3) (2016) 314-322 DO! 1015625/0866-708X/54/3/6494 EFFECT OF HOT DRYING ON THE ESSENTIAL OIL CONTENT AND COLOUR CHARACTIRISTICS OF PEPPERMINT (Mentha piperita) Nguyen Thi Kim Chi, Duong Thi Thanh Thao, Hoang Quoc Tuan* Hanoi University ofScience and Technolog); School of Biotechnology and Food technology. Department of Quality management. No I Dai Co Viet Street, Hanoi, Vietnam Email: tuanbqibft&.: vn Receipted: 28* August 2015; Accepted for publication' 29 March 2016 The main objectives of this study were to investigate the effect of different temperature of hot air drying on the qualities of dried peppermint, including essential oil content, colour parameters, and visual sensory quality and to develop mathematical models for the colour change kinetics. The drying experiments were carried out at five air temperatures, 40, 50, 60, 70 and 80 ''C- The colour parameters for colour change of the matenals were quantified by the Hunter L (whiteness/darkness), a (redness/greenness) and h (yellowness/blueness) system. These values were also used for calculation of total change (AE) as well as chroma, hue angle and Browning index. A consumer preference test was conducted with 80 consumers to assess the colour quality of 05 dried peppermint samples. The results showed that the decrease in essential oils content al high drying temperature is higher than at low temperature. Least Squares regression was used to determine the relationship between the visual sensory scores of consumer taster and the Hunter Lab values It was observed that L, a, AE and hue angle values were fitted to the zero-order model, while b and chroma were filled to thefirst-ordermodel Keywords: peppermint, colour, drying kinetic colour model 1. INTRODUCTION Peppermint (Mentha piperita) is a popular herb that can be used in numerous forms (., oil. leaf, leaf extract, and leaf water). This herbal preparation is used in cosmetics, .
