Propiedades físicas y mecánicas de películas comestibles elaboradas a base de almidón de banano

Abstract

The objective of the present research word was to determine physical and mechanical properties of edible films, elaborated with native starch from banana (Musa sapientum L.), Cavendish variety cultivar. Starch isolation was carried out by the so - called wet method (Badui, 2006) at pilot scale. For filmogenic solution formulations, different concentrations of starch, glucose and water were used. Treatments studied were: T1 (0,5 % starch – 0,25 % glucose), T2 (0,5 % starch – 0,5 % glucose), T3 (1 % starch – 0,25 % glucose) and T4 ( 1 % starch – 0,5 % glucose). To obtain the films, the casting method was used. The physical - chemical characteristics pointed out by the (Association of Analytical Communities - AOAC, 2003) were determined to the native starch of banana; selected essays were: ashes, water content, protein, crude fat, total carbohydrates (by 100 % difference as nitrogen - free extract), amylose content by the Hoover and Ratnayake (2002), and amylopectin by difference from amylose content; morphological properties were determined through Scanning Electron Microscopy (SEM), gelatinization temperature was determined through Differential Scanning Calorimetry (DSC) and viscosity was valuated through a viscometer (Rapid Visco Analyzer - RVA). Physical and mechanical properties evaluated in edible films were: thickness using a micrometer (Mitutoyo, Japan), opacity by means of spectrophotometry (VIS spectrophotometer, Jenway, United Kingdom), solubility by using an orbital shaker (mrc, Germany) and tensile strength with a texturometer (Shimadzu, Japan). Starch percentage in Cavendish banana cultivar was 88,75 % its amylose content was 15,30 %; starch granule dominant shape was ovoid with 25 to 30 μm of diameter. The peak gelatinization temperature was 73,80 °C at an enthalpy value of 14,02 J/g. The viscoamygrams showed that the maximum viscosity in banana native starch was 3836 cP at 86,8 °C and the cold dough viscosity up to 50 ° C decreased to 2087,5 cP. The four treatments analyzed showed significant differences (p ≤ 0,05) among their properties. As the concentration of banana starch in films formulation increased, its thickness increased by 0,019; 0,020; 0,024 to 0,025 as well, while film opacity was inversely proportional: higher starch percentage value resulted in opacity values of 2,14 mm-1; 2,28 mm-1; 1,73 mm-1; at 1,76 mm-1. From T1 to T4, water solubility increased considerably in each treatments (21,5 %, 26,5 %, 35,6 % and 41,01 %), as well as the tensile strength (8, 20 MPa, 10,23 MPa, 10,51 MPa and 11,47 MPa). According obtained results, the best treatment was T4 for it presented proper values regarding thickness, opacity and tensile strength; nevertheless, as regards to its solubility, it did not present proper values. It should be considered that starch concentration and the plasticizer type to be used are relevant factors in edible films composition of for these modify both, physical and mechanical film properties.