PDF《Food Hydrocolloids》

Andrade,1992). These substances are distributed in different parts of the Opuntia plants, e.g. cladodes and fruits (peel and pulp) (Sáenz, Sepúlveda, &

Matsuhiro, 2004). Nutritional and functional properties of the mucilage from Opuntia cladodes and fruits have already been re- ported (Feugang, Konarski, Zou, Stintzing, &

Zou, 2006;

Piga, 2004;

Sáenz et al., 2004;

Stintzing, Schieber, &

Carle, 2001). In addition, several studies on the composition and the properties of hydro- colloids from cladodes, seeds, and skin of cactus pear fruits have been carried out (Del-Valle, Hernández-Munoz, Guarda, &

Galotto, 2005;

Forni, Penci, &

Polesello, 1994;

Habibi, Mahrouz, &

Vignon, 2003;

Majdoub, Roudesli, &

Deratani, 2001;

Sáenz et al., 2004;

* Corresponding author. Tel.: ?506

2511 7230;

fax: ?506

2511 4710. E-mail address: [email protected] (P. Esquivel).

1 Present address: Departamento de Bioquímica, Escuela de Medicina, Uni- versidad de Costa Rica,

2060 San Pedro, Costa Rica. Contents lists available at ScienceDirect Food Hydrocolloids journal homepage: www.elsevier.com/locate/foodhyd 0268-005X/$ e see front matter ?

2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodhyd.2013.07.010 Food Hydrocolloids

35 (2014) 557e564 Stintzing &

Carle, 2005). Recently, the composition of hydrocolloids from the pulp of cactus pear fruit has been investigated (Matsuhiro, Lillo, Sáenz, Urzúa, &

Zárate, 2006). Moreover, the composition of cell wall polysaccharides from pitaya pulp was studied to enhance juice extraction through an enzymatic degradation of the mucilage in the industrial fruit processing (Ramírez-Truque, Esquivel, &

Carle, 2011;

Schweiggert, Villalobos-Gutierrez, Esquivel, &

Carle, 2009). The pitaya pericarp comprises around 50% of the fruit fresh weight (Esquivel, Stintzing, &

Carle, 2007a) being discarded during fruit processing. To the best of our knowledge, there is only scarce information about the composition of the constituents of pitaya pericarp. While the optimization of pectin extraction from the peels of pitaya fruits was previously studied (Tang, Wong, &

Woo, 2011), the aim of this work was to fully characterize the neutral sugar pro?le of different cell wall components after sequential fraction- ation of the AIR of purple pitaya pericarp. Together with the results of rheological studies, the data obtained should allow identifying promising industrial applications for this by-product of pitaya fruit processing. 2. Materials and methods 2.1. Plant material Fresh purple pitaya fruits (Hylocereus sp.) originated from Ticuantepe, Nicaragua. Fruits were harvested at fully mature ripening stage on July 2009. Fruit pericarp obtained by manual peeling was stored at ?80 C, and then freeze-dried. Subsequently, samples were vacuum-packed in aluminumepolyethylene bags and stored at ?20 C until AIR extraction. 2.2. Proximate composition of pitaya pericarp For the analyses of pericarp composition, the following of?cial AOAC methods were used: Nr. 920.15 for total solids, Nr. 920.152 for protein contents, Nr. 940.26 for ash, and Nr. 985.29 for dietary ?ber (Horwitz, 2005). Lipid contents were determined using the Soxhlet method as described by Carpenter, Ngeh-Ngwainbi, and Lee (1993). Total carbohydrate contents were estimated as the arithmetical difference of total components. The proximate composition of purple pitaya skins was based on the determinations of three different fruit lots. 2.3. Alcohol insoluble residues (AIR) The freeze-dried pericarp was ground to a ?ne powder with a Hobart FP41 food processor (Hobart, Offenburg, Germany). Samples (25 g) were boiled in aqueous ethanol (250 mL, 80% v/v) for