Mixture design applied for the study of the tartaric acid effect on starch/polyester films.

Tartaric acid (TA), a dicarboxylic acid, can act as a compatibiliser in starch/polyester blends. A mixture design was proposed to evaluate the effect of TA on the properties of starch/poly (butylene adipate co-terephthalate) (PBAT) blown films plasticised with glycerol. The interaction between the starch/PBAT and the TA has a positive effect on the tensile strength and puncture force. Additionally, greater proportions of TA increased Young's modulus. The starch+PBAT/TA and Gly/TA interactions contributed to a reduction in the water vapour permeability of the films. The inclusion of TA did not change the crystallinity of the samples. Formulations with intermediate proportions of TA (0.8 g/100 g) were shown to produce the best compatibilising effect. This was observed by DMA analysis as a consequence of the perfect equilibrium between the contributions of TA as a compatibiliser and in the acidolysis of starch, resulting in films with a tensile strength of 5.93 MPa, a possible alternative to non-biodegradable packaging.

Development of biodegradable flexible films of starch and poly(lactic acid) plasticized with adipate or citrate esters.

Biodegradable films were produced from blends contained a high amount of thermoplastic starch (TPS) and poly(lactic acid) (PLA) plasticized with different adipate or citrate esters. It was not possible to obtain pellets for the production of films using only glycerol as a plasticizer. The plasticization of the PLA with the esters and mixture stages added through extrusion was critical to achieve a blend capable of producing films by blow extrusion. Adipate esters were the most effective plasticizers because they interacted best with the PLA and yielded films with appropriate mechanical properties.

Effect of organic acids as additives on the performance of thermoplastic starch/polyester blown films.

The influence of citric acid (CA), malic acid (MA) and tartaric acid (TA) in starch/poly (butylene adipate co-terephthalate) blown films was evaluated by examining the barrier, structural and mechanical properties of the films. These properties were analysed in different relative humidities. Greater concentrations of TA and CA (1.5 wt%) produced films with improved tensile strength (6.8±0.3 and 6.7±0.3 MPa, respectively), reduced water vapour permeability and a more homogeneous structure. The compatibilising effect of MA was less efficient, as shown in the scanning electron microscopy (SEM) images. Changes in the relative humidity (RH) affected the elongation of the films, which reached values of 5.7±0.5 at 33% RH and increased to 312.4±89.5% at 53% RH. The FT-IR spectra showed no additional reactions caused by the incorporation of the additives, and the observed results are attributed to the esterification reactions and/or hydrolysis of the starch, producing films with interesting properties. This process represents an alternative to the use of non-biodegradable materials.

[Bread staling. Simultaneous effect of bacterial alpha-amylase and emulsifier on firmness and pasting properties of bread crumbs++]. / Envejecimiento del pan. Efecto combinado de alpha-amilasa bacteriana y emulsificante en la textura y en las características amilográficas de la miga.

The effect of bacterial alpha-amylase and an emulsifier on firmness and amylograph characteristics of bread crumb during storage was studied. The bread which contained these additives was less firm and stalled more slowly than the control. The enzyme and the emulsifier retarded firmness but the emulsifier inhibited the action of the alpha-amylase. The regulatory action of the emulsifier also was observed on amylograph characteristics of bread crumb (peak viscosity, cool viscosity and setback).