STUDY OF ENZYME INACTIVATION USING STEAM IN YACON (SMALLANTHUS SONCHIFOLIUS) ROOTS L. FANTE, C.F. SCHER, C.P.Z. NOREÑA 1 and A.O. RIOS Instituto de Ciência e Tecnologia de Alimentos, Universidade Federal do Rio Grande do Sul, Caixa Postal 15090 – CEP 91501-970 Porto Alegre, Brazil 1 Corresponding author. TEL: 55-51-3308-6673; FAX: 55-51-33087048; EMAIL: czapatan@ufrgs.br Accepted for Publication August 17, 2011 doi:10.1111/j.1745-4549.2011.00609.x ABSTRACT The inactivation of the enzymes polyphenoloxidase (PPO) and peroxidase (POD) and color loss with steam blanching, was studied. The yacon roots were washed and peeled, cut into 1.75  0.35-mm slices, and placed in wire baskets inside an autoclave generating steam at a temperature of 100C for 1, 2, 4, 6, 8 and 10 min. The best condition was with a time of 4 min, where it was possible to reduce the activity of POD and PPO by 84.62 and 83.76%, respectively, with losses of inulin, glucose and fructose of 30.69, 39.40 and 15.82%, respectively. Total color differ- ence and browning index values changed when compared with original color of yacon roots. These changes were higher during the first 2 min and, after this time, these parameters did not change significantly. Principal component analysis of steam blanching times in yacon too revealed no significant differences starting from 4 min of blanching. PRACTICAL APPLICATIONS Blanching is a unit operation that is used in order to achieve inactivation of enzymes that produce the browning. This procedure is used as a pretreatment before pasteur- ization, sterilization, refrigeration and freezing. Either steam or hot water can be used to blanch food. However, prolonged hot water blanching results in considerable loss of soluble sugars because of leaching. Blanching can also be used to deactivate enzymes that cause depolymerizing of polysaccharides such an inulin. This fructan has prebiotic properties and is a dietary fiber. The aim of the present work was to study the deactivation of enzymes that produce changes of color using steam in yacon roots. INTRODUCTION Yacon (Smallanthus sonchifolius) belongs to the Asteraceae family and is a native Andean plant cultivated for its tubers, which are commonly used as a food in South America. Tradi- tionally, yacon tubers and dried leaves are recommended for people suffering from diabetes or from other digestive or renal disorders (Valentová and Ulrichová 2003). The main sugar accumulate in yacon roots is sugar in the form of oligosaccharides and fructooligosaccharides (FOS), so named of fructans with a low degree of polymerization, that consist of short chains of fructose units linked by b (2→1)-glucosidic bonds (Ohyama et al. 1990; Hermann et al. 1999). They carry a single d-glucosyl unit at the nonreducing end of the a (1→2) chain as in sucrose and are thus of the inulin type (Goto et al. 1995; Hermann et al. 1999). Other carbohydrates stored by yacon are fructose, glucose and sucrose (Graefe et al. 2004). The b (2→1) bonds prevent the FOS from being digested in the colon because humans do not have enzymes to hydrolyze them (Niness 1999). Another health benefit ascribed to FOS is their bifidogenic nature, leading to the enhancement of the growth of beneficial microflora (bifidobacteria) in the colon (Niness 1999). Because the yacon roots contain little starch, they are potentially beneficial for the diet of diabetics (Neves and Silva 2007). Inulin is present in more than 30,000 vegetable products (Robinson 1995), such as cereals (wheat, barley), vegetables (onion, leek, garlic, asparagus) and fruits (banana), confirm- ing its position as a natural ingredient in the human diet Journal of Food Processing and Preservation ISSN 1745-4549 1 Journal of Food Processing and Preservation •• (2012) ••–•• © 2012 Wiley Periodicals, Inc.