Films based on derivates of amaranth for use in foods

Author(s)

Delia Rita Tapia Blácido

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia de Alimentos
• Defense date: 2006-12-12

Examining board members

Florência Cecília Menegalli; Rosiane Lopes da Cunha; Vania Regina Nicoletti; Rosemary Aparecida de Carvalho; Carlos Raimundo Ferreira Grosso

• Advisor: Paulo José do Amaral Sobral; Florência Cecília Menegalli

Abstract

Amaranth can be considered as an interesting raw material for the elaboration of biodegradable films due to its starch, protein and lipid contents. Amaranth is a natural culture of the Andean countries, but in the last few decades has been cultivated in countries like the USA and Japan. Brazil also started experimenting with this culture in scrubland soil, with good results. Faced with the need to present alternatives for the commercial use of amaranth, the objective of the present study was to investigate the capacity of amaranth flour to form biodegradable films, attending another current need, that of reducing the use of synthetic plastics. With this objective in mind, the first stage was a physical-chemical and micro-structural characterisation of the whole flour, composed of starch, protein and lipid. The gelatinisation process was also studied by way of the rheology and calorimetry of amaranth starch and flour suspensions, since this is an important process in obtaining a film-forming solution. The effects of pH adjustment and the addition of a plastifying agent (glycerol or sorbitol) on the gelatinisation of filmogenic starch and flour solutions was also evaluated, as also on the rheological properties of these solutions. A complete 22 experimental design was developed to study the effect of process temperature (Tp) and plastifier concentration (Cg glycerol, Cs sorbitol) on the properties of the flour filmogenic solution. In parallel, these filmogenic solutions were dried and the films characterised for their mechanical and solubility properties. The results were statistically analysed using response surface methodology (RSM) to evaluate the effects of the variables (Tp, Cg and Cs) on the mechanical and solubility properties of the films. Using a multi-response analysis, the optimal conditions for the elaboration of amaranth flour films were determined. These conditions were: a process temperature of 75°C and plastifier concentrations of 20.0g glycerol /100g dm or 29.6g sorbitol/100g dm (dm=dry mass). The films made with glycerol under the optimised conditions were less resistant, less soluble, more hygroscopic and more permeable to water vapour than those made with sorbitol under the optimised conditions. Both films presented a yellowish colour and relative opacity. The effect of drying temperature and relative humidity on the mechanical and solubility properties and on the water vapour permeability and drying time of the films made with glycerol and sorbitol elaborated under the optimised conditions, was studied using a complete 22 experimental design. A statistical analysis of the results confirmed that the drying temperature and relative humidity presented a significant effect on the response variables studied. The drying kinetics and sorption isotherms were also determined. The drying kinetics showed behaviour typical of polymeric materials and the sorption isotherms showed evidence of an inversion of the equilibrium moisture behaviour at high temperature and relative humidity. In the last stage of the study, the contributions of the starch, protein and lipid and their interactions to the properties of films made from flours from the species Amaranthus cruentus and Amaranthus caudatus, were studied. Thus films were elaborated from the starch, defatted flour (starch-protein), protein-lipid and protein of the amaranth species. The films were characterised with respect to their mechanical, barrier, solubility, moisture, optical, and thermal properties using differential scanning calorimetry (DSC), and the microstructure by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The inter-molecular interactions present in the films were also studied by infrared absorption spectroscopy (IRAS) (AU)