Coatings applications, starches

Edible film and coating is defined as a thin, continuous layer of edible material used as a coating or as a film placed between food components to provide a barrier to mass transfer (Balasubramaniam et al., 1997 Guilbert et al., 1997). These films/coatings have the potential to replace conventional packaging in some applications. Starches such as potato starch, cellulose... 

Starches often contain a substantial amount of salt (sodium chloride or sodium sulfate) as a residue from the modification process. Small quantities of salt in a hot starch dispersion will attack low-grade stainless steel and can cause severe corrosion of tanks, pipelines and coating application equipment. The salt content should not exceed 0.2% or 2000 ppm chloride. 

An alternative method to apply starch to paper, especially to paperboard grades, is to use a water box at the calender. Water boxes are used for wet-finishing of paper-board prior to coating application. Use of starch in the water box will increase surface strength and lessen fiber reswelling after coating application. Dilute dispersions of oxidized starch are used, frequently in conjunction with a lubricant to prevent calender roll picking. 

Nidhin,M., Sreeram,K. J.,andNair,B. U. Green synthesis of rock salt CoO nanoparticles for coating applications by complexation and surface passivation with starch. Chemical Engineering Journal, 185-186(0), 352-357 (2012a). 

The opacity is a critical property if the starch-based films are used for food coatings applications. Transparent films are characterized by low values of the area below the absorption curve. The obtained values showed that films with addition of organic acid modified starch microparticles CMSt were more transparent than films with no chemically modified starch [74]. Besides, the opacity of films decreased due to addition of CMSt, this tendency being more noticeable in sample modified with tartaric acid. Film opacity decreased in order TAMSt/Stcellulose filler composite samples is represented [75]. 

Candy starch jellies include sugar and (modilied) starch boiled to a certain viscosity and poured into a starch mold to form semi-solid jelly. Water-soluble synthetic colorants are generally added at concentrations of approximately 6% before the mixture is placed in gel-forming blocks. The shape and thickness of the final semi-transparent gel and subsequent coating with sugar sand may cause the color to become shaded. Natoal colorants are rarely used for such applications due to their low stability to temperature and pH. 

Application of nematodes in infected insect cadavers have also been described by some workers (Shapiro-Ilan et al. 2001, 2003), which enables the slow release of nematode and therefore considered effective for small-scale application. Coating the cadavers with starch and clay mixture helps in preventing rupture during storage and shipping (Shapiro-Ilan et al. 2001). 

The dominant specialty starch used in size press applications is the hydroxyalkyl derivative commonly made wjth ethylene oxide to yield a hydroxyethyl starch. Low substituted hydroxypropy1 starch has similar properties. These starches were introduced to the industry in 1950 and they have grown in importance each year. Recent expansions in production by major producers has indicated their continuing dominance of the specialty starch surface sizing and coating field. 

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