**3.1 Granule size**

The blends of starches with different granule size and amylose content contribute to new molecular interactions between the amylose/amylopectin contents presenting significant changes in the physicochemical properties (e.g. rheological, swelling power, gel, solubility, viscosity among others), which are attributed to the content of amylose, chain length and retrogradation [18–20].

The biofilms that are formed from starch are a very promising option to avoid the excessive use of plastic (polyethylene, vinyl chloride, polystyrene and urea formaldehyde) and low and/or no deterioration on the environment. Unfortunately, with the population and industrial increase, the use of plastics continues to increase year after year, which generates millions of tons of waste after use. Polyethylene degradation is highly influenced by the biotic and abiotic environment, thus limiting effective degradation. Currently, through various investigations, the development of plastics for packaging from biodegradable materials is being promoted, using starch as the main raw material [21, 22]. The wide variety of research on the use of starches from various botanical sources (e.g. potato, corn, wheat, tapioca, rice and others) and its low cost together with comparable characteristics for film formation have shown that it is an efficient packaging raw material and a possible substitute for polyethylene, however, there are still physicochemical properties that are still under experimentation, taking into account the permeability to water vapor, mechanical properties, glass transition and hydrophobicity. The film formation process from starch granules has been described by different authors, the quality of the film is greatly affected by the amylose/amylopectin/plasticizer (glycerol) ratio, the latter being the most widely used. The content of amylose/amylopectin, a variation in the intrinsic properties of the film can be observed due to the deviation in the content of phosphorus, molar mass of starch and the biochemistry of amyloplast and chloroplast [23]. Corn is a predominant source of starch (65%) produces a film with a higher percentage of elongation, better oxygen barrier properties and a high elastic modulus, in addition [24]. The formation of biofilms from blends of cassava/corn starch with cellulose was shown to have a hydrophobic effect by reducing the affinity of starch films with water and considerably reduced the rate of permeability to water vapor, thus improving their properties. In addition, the amylose content promotes the production of a more hydrophobic film, due to the strong interactions of intermolecular bonds with glycerol [25]. New techniques for incorporating particles onto others, as reported by Farrag, et al. [26], I present reported that they prepared starch microparticles with donut-shaped morphology from two different botanical origins (type A and C for corn and pea starch granules, respectively) by means of a simple hydroalcoholic heat treatment. The donut-shaped microparticles were loaded onto films of the same botanical origin, generating greater thermal stability of the films produced. In addition, adjusting the percentage of microparticles in the thermoplastic films allowed to supply the desired amount of oxygen and water vapor to the packaged food. This is very important to keep packaged foods fresh and healthy for as long as possible. Emulsions are systems that are characterized by presenting small

dispersed droplets of an immiscible liquid phase in another liquid phase, based on many applications in different industries (eg food, nutraceutical, cosmetic, hygiene, detergents, pharmaceutical and medical), however, to stabilize these emulsifying systems, synthetic surfactants (Tweens 20/60/80) or emulsifiers of animal origin (albumin/casein) are used [27]. However, they have disadvantages in their formulation because they generate foam retention due to the trapped oxygen and interactions with other suspended molecules and even the surfactant that is not compatible, an emulsion being key for the production of various food and pharmaceutical products, it is necessary to produce emulsions with solid particles of vegetable origin to stabilize the emulsions, which is called Pickering emulsions [28]. Compared to surfactant stabilized emulsions, Pickering emulsions tend to be more stable against Ostwald ripening and coalescence. Currently, starch and cellulose are used to create Pickering emulsions. Starch for its different physicochemical properties (generally recognized as safe, non-allergenic, abundant and cheap). Unfortunately, starches are still being modified to make Pickering-type emulsions, the most widely used is succinate with octenyl succinic anhydride (OSA) reagent for emulsion production. So far, the information on Pickering starch emulsions is very scattered. The links between the manufacture of Pickering emulsions and their applications are largely absent. The lack of such links seriously undermines our research efforts to better utilize emulsions for practical applications [29]. Native starch granules are not suitable for creating stable Pickering emulsions. The starch is modified to be suitable for making a Pickering emulsion. However, future trends suggest using starch blends of granule size ≤10 μm that can be compatible with starch concentration, oil and water volume, pH, ionic strength, storage conditions, processing and presence of other components for obtain a drop size (1–100 μm) [29]. Amaranth starch has shown to have sizes ≤2 μ, which is a potential candidate to produce emulsifying systems without modifying the molecular structure by chemical agents, however, physical modifications will have to be used (e.g. temperature, pH, pressure, radiation, homogenization at high revolutions among others) to obtain favorable and applicable results [30].

Grinding on native starch granules to reduce the particle size, proved to be favorable to elaborate a Pickering emulsion system [31]. The high pressure treated starch chips and ground starch particles are partially gelatinized. They can represent a mixture of rigid particle and flexible polymer model systems in emulsions. The deformability of the starch particles can be modified in situ in Pickering emulsion systems. Heating Pickering emulsions can gelatinize starch granules to different degrees. Heating can make the boundaries between adjacent particles indistinct. During heating, some amylose and amylopectin molecules leak out of the swelling granules, causing a stabilizing layer of starch granules, becoming a layer of swollen granules interpenetrated with leached starch (amylose) polymers. In this type of emulsion systems with partially gelatinized starch granules, rigid particles (granules) and flexible polymers (leached starch molecules) coexist [32, 33]. In general, the droplet size of Pickering emulsions can be adjusted using compatible starch blends, different sizes, use of physical methods, suitable starch concentrations, and processing methods.

## **3.2 Extrusion**

Extrusion is a continuous processing method, it involves high pressure and temperature in a short time. Its main function is to mix various components. The extrusion process allows the gelatinization of the starch, the denaturation of the proteins and even the molecular degradation due to the effects of high shear depending on the screw to be used, which in turn affects the physicochemical properties of the

*Advances and Trends in the Physicochemical Properties of Corn Starch Blends DOI: http://dx.doi.org/10.5772/intechopen.101041*

extrudates. Many studies have been conducted to explore the relationships between extrusion processing parameters and non-food starch characteristics in order to improve processing control [34]. However, little scientific evidence has attempted to understand the relationships between the physicochemical properties of extrudates and the molecular characteristics of starch after the extrusion process using starch blends, because using starches in the native state affects the bostwick flow (viscosity and/or consistency) on the extruder barrel causing a process obstruction, therefore, previous parameters for an excellent extrusion must be considered, such as the amount of starch moisture, the temperatures of each zone of the extruder, as well as the time and type shear stress, which is crucial to achieving product quality and developing novel products [35]. The use of corn starch/cassava blends provides different degrees of gelatinization and some existing air microcells in the extrudates, attributing this effect to the extension of the puff and the fine structures of the extrudates when they were exposed to different temperatures, residence times. in the extruder and the amount of moisture present in the starch sample [36].

### **3.3 Encapsulation**

The microencapsulation process by spray drying method allows the use of a large number of wall materials. It is essential to know the type of starch to use, it must present characteristics such as high solubility, low swelling power and viscosity, thus allowing effective encapsulation, since it can influence the properties of the emulsion, the retention of active principle, flavor and the end product shelf life. Currently there are no reports of works in which a mixture of two or more starches is implemented to be used as wall material due to the increase in viscosity, however, new trends such as using blends of porous starches, which are naturally derived from starch native by physical, chemical or biological methods. There are pores, holes and/or openings with diameters less than one micron in the structural lattices, through which molecules with smaller particle size can enter the polymeric structure and become encapsulated. The use of these possible starch blends will be an option and research topic to avoid conventional modifications on the structure of the starch, being an environmentally friendly option and without remnants of solutions with chemical reagents [37].
