ORIGINAL PAPER Effects of Enzymatic Liquefaction, Maltodextrin Concentration, and Spray-Dryer Air Inlet Temperature on Pumpkin Powder Characteristics Forough Shavakhi & Huey Chern Boo & Azizah Osman & Hasanah Mohd. Ghazali Received: 23 February 2011 /Accepted: 8 September 2011 # Springer Science+Business Media, LLC 2011 Abstract This study was conducted to investigate the effects of three variables namely cellulase (Celluclast, Novozymes, Denmark) concentration (0–1%, v/w (x 1 )), maltodextrin (MD) concentration (15–30%, w/w (x 2 )), and spray-dryer air inlet temperature (150–190 °C (x 3 )) on pumpkin powder charac- teristics using enzymatically macerated pumpkin with Pectinex® Ultra SP-L (2.5%, v/w). The powder character- istics considered as response variables in response surface methodology were process yield, moisture content, sticki- ness, water activity, and hygroscopicity. Results indicated that the response surface models were significantly (p ≤ 0.05) fitted for all response variables in the studied indepen- dent variables range. The concentration of Celluclast and MD should be considered as critical factors which may increase process yield of pumpkin powder. The effect of Celluclast concentration on pumpkin powder characteristics especially for process yield and stickiness was noticeable. The main effect of MD and quadratic term of Celluclast had the most significant effect on stickiness. Negative interaction value of MD with Celluclast indicated that stickiness decreased when mixture of MD and Celluclast was used and also Celluclast reduced the impact of air inlet temperature on stickiness. The overall optimum region resulted in a desirable powder characteristics was predicted to be obtained by combined level of air inlet temperature 180 °C, Celluclast 0.7% (v/w), and MD 23% (w/w). The theoretical and experimental validation ensuring the adequacy of the response surface models described the changes in physical properties of powder as a function of Celluclast, MD, and air inlet temperature. Keywords Celluclast® 1.5 L . Maltodextrin . Pectinex® Ultra SP-L . Pumpkin . Spray drying Introduction Extending shelf life with minimum packaging requirements and reducing shipping weights are the aims of drying food products while diversified fruit and vegetable powders can be used in many products such as instant soups, snacks, bakery, beverage, dairy, candy, ice cream, baby food, and pasta (Pua et al. 2007; Youssefi et al. 2009). Pumpkin powder is the main processed product of pumpkin which can be easily stored for a long time and conveniently used in processed food such as noodle, bread, and cake (Que et al. 2008). Spray drying is a highly appropriate process for heat-sensitive products such as foods and results in powders with good quality, low water activity, and easier transport and storage (Tonon et al. 2009). It has been widely used in many fruits and vegetables such as blackcurrant, apricot, raspberry (Bhandari et al. 1993), guava (Chopda and Barrett 2001), pineapple (Abadio et al. 2004), tomato (Goula et al. 2004), cactus pear (Rodriguez-Hernandez et al. 2005), mango (Cano- Chauca et al. 2005), acerola (Righetto and Netto 2005), watermelon (Quek et al. 2007), orange (Chegeni and Ghobadian 2005), gac (Tran et al. 2008), ginger (Schweiggert et al. 2008), and acai (Tonon et al. 2008, 2009). Enzymatic maceration has considerable importance in the fruits and vegetables processing for the production of nectars and pulps (Sreenath and Radola 1986; Bhat 2000). Macerating enzymes hydrolyse soluble pectin and cell wall components of fruits and vegetables leading to a decrease in F. Shavakhi : H. C. Boo : A. Osman : H. M. Ghazali (*) Faculty of Food Science and Technology, Universiti Putra Malaysia, UPM 43400, Serdang, Selangor, Malaysia e-mail: hasanah@putra.upm.edu.my Food Bioprocess Technol DOI 10.1007/s11947-011-0686-4