Consolidado diario de campo

Carrier materials for spray drying should be selected on the basis of their physicochemical properties like crystallinity, solubility, sensory characteristics, emulsifying properties and molecular weight as it pertains to the application in question (Sollohub & Cal, 2010). The economic feasibility of their use should also be considered, since many remain prohibitively expensive. It has been established that the highest losses of volatile compounds during spray drying occur before the

82 formation of the dry crust in the early stages of drying (Patel et al., 2009). The addition of carrier materials to the feed can modify the drying attributes of the microcapsule by enhancing dry crust formation and increasing the hydrophilicity of the coating (Woo & Bhandari, 2013; Costa et al., 2015). A wide variety of natural and synthetic polymers can be used as carrier materials. Good solubility in water is an important requirement for most spray drying applications since aqueous solutions are typically used as feed material (Ré, 1998). Low viscosity and good emulsifying and film- forming properties are also desirable (Costa et al., 2015). Natural gums like carrageenan, gum arabic and alginates have been successfully used as carrier materials, along with proteins of varied origin and other complex carbohydrates like waxes and maltodextrin. The selection of carrier material often involves a trial-and-error approach in which different options are evaluated based on their microencapsulation efficiency in terms of process yield, core material retention, storage stability and particle size and morphology, amongst others (Gharsallaoui et al., 2007).

Carbohydrates like maltodextrin, inulin and lactose have been widely used as encapsulating agents due to their generally low viscosity at high concentrations and good solubility in water, but they often lack the good interfacial properties associated with gums and proteins (Sollohub & Cal, 2010). Maltodextrin is a polymer of D-glucose obtained from acid or enzymatic hydrolysis of corn starch, and is available in different dextrose equivalents (DE), which correspond with the degree of hydrolysis of the starch. The DE is therefore also inversely related to the average molecular weight (Costa et al., 2015). Maltodextrin is commonly used in spray drying due to its neutral smell and taste, high solubility in cold water, low cost, low hygroscopicity, and low viscosity at high concentrations (Ré, 1998). It has also been shown to exhibit an antioxidant effect and good volatile retention. It lacks good emulsifying properties, but this can be addressed by the addition of a second carrier which does provide that function, like gum arabic (Costa et al., 2015). Gum arabic, a polysaccharide containing mainly D-glucoronic acid, D-galactose, L-rhamnose and L-arabinose, is one of the most commonly used carriers due to its excellent solubility, low viscosity, high oxidative stability and good emulsifying properties, which is attributed to a small protein fraction (2%) found among its constituents. This makes it an excellent choice for the encapsulation of lipids (De Barros Fernandes et al., 2012). High costs and limited supplies often prohibit the more widespread use of gum arabic, however, and alternatives have been proposed, e.g. mesquite gum (Jimenez-Aguilar et al., 2011).

Inulin, produced on a commercial level mainly from extracts of chicory (Cichorium intybus) roots, Dahlia (Dahlia pinuata) and Jerusalem artichoke (Helianthus tuberosus), is a polysaccharide and non-digestible dietary fibre composed of β(2→1) linked D-fructosyl residues (n = 2–60) which has been applied as carrier agent in a number of spray drying operations, besides its other uses in the food and pharmaceutical industries as fat replacer, protein stabiliser, texture modifier and diagnostic aid (Mensink et al., 2015a; Mensink et al., 2015b). Inulin is only partially hydrolysed in the

83 gastrointestinal tract and does not result in the production of monosaccharides, and therefore does not result in elevated blood glucose concentrations (Kolida et al., 2002; Mensink et al., 2015b). This would be an important consideration in the selection of a carrier material for an antidiabetic nutraceutical, since the beneficial hypoglycaemic effects of the bioactive compounds would be diminished if a carrier with a high glycaemic index were part of the formulation. Inulin has the additional advantage of acting as a prebiotic by stimulating the growth of beneficial gastrointestinal bifidobacteria (Kolida et al., 2002). The increased consumption of dietary fiber has been linked to a lower risk for cardiovascular diseases, lower body mass index and improved gastrointestinal health (Slavin, 2013). The latter is particularly associated with prebiotic dietary fibers, i.e. those which stimulate the growth and/or activity of specific gut microflora to the benefit of the host. Inulin has been shown to stimulate the growth of the beneficial genus Bifidobacterium in a number of studies (Costabile et al., 2010; Ramnani et al., 2010). A number of large-scale cohort studies have demonstrated a strong inverse relationship between the regular consumption of dietary fiber and the development of T2D (Meyer et al., 2000; Hopping et al., 2010; Nazare et al., 2011; Slavin, 2013). Gargari et al. (2013) studied the effects of high-performance inulin supplementation on glycaemic control indices and antioxidant status in women (n = 49) with T2D. The control group (n = 25), who received 10 g per day of maltodextrin for 2 months, had significantly higher (P < 0.05) fasting plasma glucose (8.74%), glycosylated haemoglobin (10.43%) and malondialdehyde (37.21%) levels than the treatment group (n = 24), who received 10 g of inulin per day for the same period. The inulin group also had significantly higher (P < 0.05) superoxide dismutase activity (4.36%) and total antioxidant capacity (18.82%) than the control group. Yang et al. (2012) reported that the combined intake of catechin-rich green tea and inulin may have an anti-obesity effect in obese and overweight adults. Experimental subjects who received a green tea infusion with added inulin for 6 weeks had significantly reduced body weight and fat mass compared with the control group, who received only the green tea infusion.

Proteins exhibit many functional characteristics which allow their successful application as spray-drying carriers. Two of the most long-established carrier proteins are gelatin, derived from animal collagen, and milk or whey proteins. The latter has been used extensively in the dairy industry for the production of microencapsulated milk fat (e.g. instant coffee creamers) by spray drying and is often associated with very favourable product yields (Young et al., 1993; Gunasekaran et al., 2007). In addition, the use of pea protein concentrates as carrier for spray-dried ascorbic acid and alpha-tocopherol has been investigated with promising results (Pierucci et al., 2006, Pierucci et al., 2007). The use of proteins should take into account the processing conditions, as heat treatment could lead to denaturation of the protein structure and subsequent loss of its desired functional properties. Other limitations associated with the use of some proteins include the potential of allergenicity, precipitation in products with pH near the iso-electric point of the carrier, and the

84 matter of religious or cultural prohibitions against the consumption of some animal-derived products (Sollohub & Cal, 2010).