Phenolic compounds from residual sources

1.2 Phenolic compounds

1.2.2 Phenolic compounds from residual sources

Processing of fresh natural materials and fabrication of target products lead to the production of many by-products, which are actually wastes of food industry. Even at home, skin of orange, banana, onion and potato, seeds of cherry, apricot and peach are thrown out. The fact that fresh natural materials are rich in phenolic compounds makes it obvious that residues of them will also contain phenolics. Many studies have been performed on the phenolic content of wastes of food industry.

Wine by-products are of great interest due to the fact that grapes and wine are good sources of phenolic compounds, which were shown in previous section. Yi et al. (2009) reported that grape pomace powder from the production of “Cabernet Sauvignon” and

“Royal Rouge” wines contained 250±2.6 and 480±2.8 mg gallic acid equivalents (GAE)/100 g fresh weight (FW) phenolics and 131±2.1 and 302±3.2 mg cyanidin 3-rutinoside equivalent/100 g FW anthocyanins with antioxidant capacity of 52.8±0.3 and 79.0±0.1 µM trolox equivalent/100 g FW, respectively. Alonso et al. (2002) showed that by-products of different wines contained polyphenols such as: gallic acid, furfural, p-OH-phenethyl alcohol, catechin, vanillic acid, syringic acid, epicatechin, caftaric acid, trans-coutaric acid, clorogenic acid, and trans-p-coumaric acid. Similar phenolic compounds were reported in the study by Lafka et al. (2007).

Garcia et al. (2009) showed that apple pomace from the cider industry contained 3.9-13.9 g GAE/kg dry matter (DM) with 4.3-12.5 g ascorbic acid equivalents/kg DM antioxidant capacity. Sixty phenolic compounds were positively identified by Sanchez-Rabaneda et al. (2004) in apple pomace; phloridzin, chlorogenic acid, quercetin and quercetin glycosides were emphasized among the identified components.

Bayberry pomace was found to have total phenolic content of 27.7-47.4 mg GAE/g DM with 78.5-100.6 mg trolox equivalents/g DM antioxidant capacity (Zhou et al., 2009).

Sojka & Krol (2009) reported that industrial seedless black currant pomace had total phenolic content of 1855.5-2285.6 mg (-)epicatechin equivalents/100 g pomace and antioxidant capacity of 93.3-126.5 µM trolox equivalents/g pomace.

During extraction process depending on the solvent some soluble compounds other than phenolics can also be extracted. Manto Negro red grape (Vitis vinifera) pomace was found to contain 3.27±0.10% (dry matter) of soluble sugar, 6.20±0.30% of soluble pectins and 74.5±2.43% of total dietary fibre (Llobera & Canellas, 2007). Grape pomace powder from the production of “Cabernet Sauvignon” and “Royal Rouge”

wines contained 5.32 and 6.03 g/100 g FW of soluble sugars and 56.9 and 55.4 g/100 g FW of total dietary fiber, respectively (Yi et al., 2009).

9 1.3 Encapsulation

Encapsulation is a technology used in food industry to coat small particles of ingredients or even whole material (nuts, confectionary products, etc.).

Microencapsulation is one of the technologies of encapsulation. Used by the food industry for more than 70 years, microencapsulation can be defined as a process of sealed packaging by coating material (wall material) of miniature substances (solid, liquid, or even gaseous materials) in microcapsules or by embedding them in a homogeneous or heterogeneous matrix from which coated material (core material) can be further released under specific environmental conditions and at the specific rate (Desai & Park, 2005). Reduction of the susceptibility to environmental factors such as, light, moisture or oxygen, controlled release of the core material to the outside environment, easier handling, masking of the taste of core material, and dilution of core material in coating material when it should be used in small amounts are the main reasons for the application of microencapsulation in food industry (Shahidi & Han, 1993).

1.3.1 Encapsulation technologies

Many different types of microcapsules are produced using wide range of coating materials and different microencapsulation processes such as: spray drying, spray chilling, spray cooling, air suspension coating, fluidized bed coating, coacervation, emulsion, nanoparticles, extrusion, freeze drying, centrifugal extrusion, and liposome entrapment (Augustin & Hemar, 2009; Desai & Park, 2005; Gibbs et al., 1999; Gouin, 2004, Shahidi & Han, 1993).

Spray drying is a well-established method used in different sectors of food industry. It is most commonly used in microencapsulation due to its low cost and its ability to

convert fluid material into solid or semi-solid material in a single step. The basic process of microencapsulation by spray drying involves dissolving of core ingredient in the dispersion of coating matrix. Contact with hot air causes rapid moisture loss in the droplets. In addition, temperature of the droplets remains relatively low, so high temperatures of air do not affect products’ quality negatively (Augustin & Hemar, 2009; Roustapour et al., 2009). However, operating under high temperatures can cause inactivation and damage of some heat-sensitive food components like vitamins and enzymes (Yoshii et al., 2008).

Freeze drying is another method used for the microencapsulation for almost all heat-sensitive materials. This method is also known as lyophilization or cryodesiccation.

The principle of operation is based on the direct sublimation from the solid state to the gas phase at low temperature and pressure. When compared to spray drying, freeze drying is more expensive and time consuming process. Microencapsulation by freeze drying is performed by dissolving core material in the coating material matrix which is then lyophilized. The resulting dry product is then grinded to a fine powder containing particles with uncertain forms. Freeze drying can be used in the encapsulation of water-soluble essences, aromas and drugs (Desai & Park, 2005). Freeze drying results in the formation of more porous particles when compared to spray drying (Augustin &

Hemar, 2009).

Emulsions are used to deliver lipophilic food components (carotenes, tocopherols, etc.).

However, water phase of the emulsion can be also involved in the delivery of water-soluble food components (Augustin & Hemar, 2009). Nano-emulsions are formed under treatment by high-energy input such as ultrasonication or by high-pressure homogenization and microfluidization. Nano-emulsions with particle size range of 50 to 200 nm are transparent while emulsions with particle size up to 500 nm have milky appearance (Tadros et al., 2004). It has been shown that particle size distribution of emulsion is important parameter for encapsulation efficiency and it also defines

stability, color and rheology of the emulsion (Jafari et al., 2007a). Low-energy emulsification and high-energy or high-pressure homogenization are two methods used in the production of nano-emulsions. Phase inversion temperature technique is an example of low-energy emulsification. Low-energy emulsification methods have several disadvantages, such as careful control of temperature, large amount of surfactant requirement and restricted application to large-scale industrial productions (Seekkuarachchi et al., 2006). On the other hand, high-energy emulsification methods, such as ultrasonication and microfluidization have several advantages and are more applicable because of ability to control particle size distribution and to prepare emulsions with different types of materials (Seekkuarachchi et al., 2006).

Generally, nano- term is added to a technology or process in which the material is at the 10^-9 meter scale in size. Nanotechnology is a developing interdisciplinary field in which knowledge from different sciences, including physics, chemistry and engineering, are brought to one area. It is also studied and applied in food science. Unique and novel physical, chemical and biological properties which are offered by nanoscale structures caused an increased interest of the application of nanotechnology in the encapsulation of food ingredients. Nanoencapsulation has been proposed as a different type of encapsulation. Nano-emulsions and nanocapsules are the products of this novel encapsulation technology. The advantages of nanoencapsulation are ease of handling, enhanced stability and bioavailability, change in flavor character, and moisture- and pH-triggered controlled release (Neethirajan & Jayas, 2011). Recently, only few studies on the nanoencapsulation are present in the literature. Semo et al. (2007) showed that casein micelle can be used in the nanoencapsulation of hydrophobic food ingredients such as vitamin D2 for potential enrichment of low- or non-fat food products. β-carotene encapsulated in biopolymer ultrafine fibers of edible zein prolamine by means of electrospinning presented a remarkably good protection against oxidation when exposed to UV-Visible irradiation (Fernandez et al., 2009). Sunflower oil in water nano-emulsions prepared by high pressure homogenization (5 passes at 300 MPa) had

mean particle size distribution in the range of 100-200 nm (Donsi et al., 2012). In the same study, antimicrobial activities of carvacrol, D-limonene and trans-cinnamaldehyde were found to be dependent on the formulation nanoemulsion-based delivery systems.

1.3.2 High-energy ultrasonication method

Ultrasound waves are sound waves beyond the audible frequency range. When ultrasound wave passes through liquid medium which contains dissolved gas it causes a phenomenon known as acoustic cavitation, which leads to the generation of physical forces including microjets, shear forces, shock waves and turbulence (Chandrapala et al., 2012). In addition, friction between the probe, medium and container’s walls leads to the heat generation. There are many applications of ultrasound in different areas of food industry. McClements (1995) described that ultrasound can be used in the detection of presence/absence, thickness, level and foreign body, in the measurement of flow rate and temperature, and in determination of microstructures. In a recent review by Chandrapala et al. (2012) other types of applications, such as emulsification, filtration, viscosity modification, diary systems and tenderization are described.

Ultrasonication is successfully applied in the production of micro- and nano-emulsions.

Sound waves with low frequencies (e.g. 20 kHz) are able to form strong shear forces, but waves with higher frequencies generate weaker shear forces. Therefore, emulsions are produced only by ultrasound waves with high intensity and low frequency (16-100 kHz) (Chandrapala et al., 2012). There are many parameters which affect the emulsification process including position of the ultrasonic probe in the relation to the liquid-liquid interface, viscosity of the continuous phase, ultrasonic power and processing time (Behrend & Schubert, 2000; Cucheval & Chow, 2008; Jafari et al., 2006; Jafari et al., 2007a).

After sonication of whey protein dispersions at 20 kHz and 750 W, it was observed that particle size distribution curve shifted to the left for more diluted dispersions. It was also reported that longer time of ultrasound treatment resulted in the formation of smaller particles when compared to short time processing (Gordon & Pilosof, 2010).

In another study by Leong et al. (2009) it was shown that ultrasonication (400 W, 20 min) of triglyceride oils in water resulted in the production of transparent nano-emulsion with mean particle size less than 40 nm.

Among the key parameters of emulsification using ultrasound, special attention should be paid to the optimization of applied power. Kentish et al., (2008) performed a study in which they showed that droplet particle size decreased with increasing power then particle size reached its minimum at an intermediate power application and after that increased at higher power levels. The same phenomenon was also observed and described as “over-processing” in the studies performed by Desrumaux & Marcand (2002) and Jafari et al. (2006).

1.3.3 Encapsulating materials

There are many different types of encapsulating/entrapping materials used in encapsulation of food ingredients. They can be used separately or in the mixture of two or more different materials. Coating material used for the encapsulation should meet the required criteria, such as compatibility with the food product, mechanical strength, appropriate thermal or dissolution release, and appropriate particle size (Gharsallaoui et al., 2007). Wall materials can be composed of sugars, gums, proteins, natural and modified polysaccharides, lipids and synthetic polymers (Gharsallaoui et al., 2007;

Gibbs et al., 1999). Generally, encapsulating materials used in food industry are

considered as biomolecules. There are different sources of biomolecules, such as plants, animals, and microorganisms. Overview of coating materials with their origins is given in the Table 1.4. The most commonly used materials such as maltodextrins and gum arabic belong to the polysaccharides category (Wandrey et al., 2010).

Table 1.4 Microencapsulating materials overview and their sources (Wandrey et al., 2010)

15 1.3.3.1 Maltodextrin

Maltodextrin is a functional derivative of starch. It is formed by hydrolysis of starch (usually corn or potato starch in US and wheat starch in Europe) by acid, enzyme, or acid/enzyme combinations (Wandrey et al., 2010). Dextrose equivalent (DE) of maltodextrin is less than 20. DE term is defined as a measure of reducing power of a starch derivative compared with D-glucose on a dry-weight basis and is higher for greater extent of starch hydrolysis (Wang & Wang, 2000). Starch and some starch derivatives with their DE are shown in the Fig.1.1.

Fig. 1.1 Classification of starch hydrolysates based on the dextrose equivalent (DE) value (Wandrey et al., 2010).

Maltodextrins are cold-water soluble, easily digestible, creamy white powders which are tasteless or moderately sweet. Klinkesorn et al. (2004) studied stability and rheology of oil-in-water emulsions which contained maltodextrins with different DE.

They found that, minimum amount of maltodextrin required to promote rapid creaming decreased as the DE of maltodextrin decreased. They also reported that, at high concentrations maltodextrins with lower DE cause higher relative viscosity. Wang &

Wang (2000) reported DE values of 8.2, 5.9 and 14.2 for commercial corn, potato and rice maltodextrins, respectively. They emphasized that, high concentrations of high molecular weight saccharides (low DE) in maltodextrins contributed to higher viscosity and freezing temperature, less water sorption and greater tendency to retrogradation.

Maltodextrin with 10 DE had higher phenolic retention when compared to 20 DE in the study performed on encapsulation of açai pulp by spray drying (Tonon et al., 2009).

Cactus pear (Opuntia streptacantha) was encapsulated by spray drying using two types of commercial maltodextrin with DE of 10 and 20, and better binder properties were reported for maltodextrin 10 DE when compared to maltodextrin 20 DE which resulted in greater capacity of retention of vitamin C after encapsulation (Rodriguez-Hernandez et al., 2005). Microencapsulated powders of cloudberry (Rubus chamaemorus) phenolics prepared with maltodextrin 5-8 DE were remarkably better in the encapsulation yield and efficiency when compared to powders which contained maltodextrin 18.5 DE (Laine et al., 2008).

1.3.3.2 Gum arabic

Gum arabic (GA) is naturally occurring, edible and gummy exudate collected from the stems and branches of Acacia senegal and, to a lesser extent, from Acacia seyal that is rich in non-viscous soluble fiber (Ali et al., 2009; Yadav et al., 2007). Gum arabic is composed of arabinogalactan oligosaccharides, polysaccharides, and glycoproteins and

its chemical composition is dependent and may vary due to the factors such as source, climate, season, age of trees, rainfall, time of exudation, etc. (Wandrey et al., 2010). It is colorless, odorless and tasteless and does not add any odor, taste or color to the product it is added. Gum arabic is both cold- and hot-water soluble and it is a good emulsifying agent. Gum arabic is used as a stabilizing, emulsifying and thickening agent in the food industry (in beverages, candy, confections, etc.) and it is also used in pharmaceutical, textile, cosmetics, pottery and lithography industries (Verbeken et al., 2003).

Shiga et al. (2001) reported that blending of gum arabic and cyclodextrin in the feed liquid in the encapsulation of flavors by spray drying resulted in an increase of flavor retention. Microcapsules of cinnamon oleoresin obtained by spray drying and prepared with gum arabic:maltodextrin:modified starch (4:1:1) were spherical and had smooth surface, whereas microcapsules prepared from gum arabic had some dents and capsules prepared from maltodextrin and modified starch were broken and not complete (Vaidya et al., 2006). Better emulsion stability and better stability against environmental factors such as NaCl concentration and thermal treatments has been reported for the soybean-stabilized oil-in-water emulsion in the presence of gum arabic (Wang et al., 2011).

Gum arabic was successfully used in the production by spray drying of açai powder and particles produced with it exhibited the lowest mean diameter when compared to maltodextrin and tapioca starch (Tonon et al., 2009). It was also used as a carrier agent in the encapsulation by microfluidization and spray drying of red rasberry (Rubus idaeus) puree (Syamaladevi et al., 2012). Maltodextrin and gum arabic were used separately as carrier agents in the production of lemon juice powders (Martinelli et al., 2007).

1.3.4 Encapsulation of food ingredients containing polyphenols

Many studies on the encapsulation of phenolic compounds from natural sources have been performed over the last decade. Generally, core materials in these studies were homogenized natural sources or extracts from them.

Tonon et al. (2009) prepared açai powder from açai (Euterpe oleraceae Mart.) pulp by spray drying. In this study maltodextrin (10 DE and 20 DE), gum arabic and tapioca starch were used as carrier agents and powders produced with maltodextrin and gum arabic exhibited high retention of polyphenols and antioxidant capacity during storage at 40 °C for 15 days at two different relative humidities (32.8% and 84.3%).

Bioactive compounds from cactus pear (Opuntia ficus-indica) pulp were microencapsulated by spray drying using maltodextrin 10 DE and inulin as coating materials by Saenz et al. (2009). In this study, encapsulation yield of betacyanin and indicaxanthin reached values above 98% and 92%, respectively, whereas, phenolic compound encapsulation yield values ranged from 23% to 81%. Produced powder was suggested to be used as a red colorant and as a functional food due to its high antioxidant content.

Sanchez et al. (2011) dissolved maltodextrin (10 DE) in wine to 20% concentration (total weight basis) and freeze dried prepared mixture to obtain “wine powder”. Total phenolic content of “wine powder” made from red wine Cabernet Sauvignon remained essentially constant during the storage period.

Gum arabic and maltodextrin (25 DE) were added directly in different combinations to the concentrated immature acerola juice to give a total of 50% soluble solids and then this mixture was spray dried (Righetto & Netto, 2005). Critical water activity range, in

which physical transformations were observed in the encapsulated samples, was 0.33-0.43, depending on the storage temperature.

In the encapsulation of Elderberry (Sambucus nigra L.) juice by spray drying five different wall materials were tested: maltodextrin (4-7 DE), gum acacia, isolated soya protein, soya protein powder, and soya milk powder (Murugesan & Orsat, 2011). All wall materials were added at the total juice solids to coating material ratio of 5:1, 5:2, 5:3, 5:4 and 1:1 (weight basis). The highest total phenolic content was found to be 48.1 mg GAE/g for powder produced with gum acacia at 1:1 ratio. In general, powders with gum acacia had higher phenolic content when compared to powders with maltodextrin and all other soya products. In addition, gum acacia followed by maltodextrin showed the best results in phenolic content retention during storage at different conditions and different packaging materials.

Cooking stability in pasta of microencapsulated garcina cowa fruit extract produced by spray drying with whey protein isolate as a carrier agent was studied by Pillai et al.

(2012). It was reported that pasta prepared with powder with 1.5:1 core-to-coating ratio which was spray dried at 90 °C outlet temperature exhibited the highest antioxidant activity when compared to powder with 1:1 core-to-coating ratio and to powders produced at 105 °C outlet temperature. There is no explanation regarded to the change of total antioxidant capacity due to the cooking process.

1.4 Aim of this study

In the last decade many studies have been performed on the possible sources of natural antioxidants, since there is a demand in different industries towards the replacement of synthetic antioxidants by natural ones. However, the factors such as loss of quality during storage and processing, unpleasant taste, and in some cases, off-color decrease

the effectiveness of the utilization of natural antioxidants in food products.

Encapsulation of these functional food ingredients can improve their quality attributes and mask unwanted features. In addition, food ingredients which are encapsulated in particles or dispersed in emulsions with particle size less than 200 nm can be released under control depending on the pH or temperature of the environment and bioavailability of the coating material.

There is a lack of study on the encapsulation of phenolic materials from the residual sources. In addition, there are limited researches on nano-emulsion containing food ingredients other than oils. The primary aim of this study was to develop a method to obtain nano-emulsion containing dry polyphenolic powder extracted from sour cherry pomace. It was also aimed to investigate the effect of degritting of the extract of sour cherry pomace on the encapsulation efficiency and particle size distribution of the emulsions. It was important to obtain capsules of both unpurified and degritted

Belgede EFFECT OF NANOENCAPSULATION OF PURIFIED POLYPHENOLIC POWDER ON ENCAPSULATION EFFICIENCY, STORAGE AND BAKING STABILITY (sayfa 24-0)