Fruit pectins – A suitable tool for screening gelling properties using infrared spectroscopy

Found in higher plants, pectins are natural hydrocolloids whose extraction is controversial as it is condition-dependent. To optimize the methodology for extracting and isolating pectins and verifying the effect on their structural characterization, a factorial 23 assay was planned, using the following independent variables: pH, duration of heating and nature of alcohol in fruits with different kinds of morphologies. The fruits were grouped into those that produce good jams and jellies (group I), those that have a variable chemical composition and contain fiber (group II), and those that contain starch (group III). The results were compared using variance analysis and Duncan test. The degree of methoxylation (DM) of the pectin isolated from the mesocarp of citrus and guava fruits (whole) was associated linearly with all independent variables. However, the pectin yield was influenced only by pH and duration of heating. The interaction between the nature of alcohol and the duration of heating were shown to be significant, a longer heating time and ethanol being better for the two kinds of fruit. In group I, the pectins isolated showed best DM associated with high yield, whilst group II yield was below the limit for producing jams and jellies, despite high DM. Group I fruits displayed characteristics that favor gel formation, whilst group II and group III proved to be deficient in at least one of the dependent variables. This study has validated as analytical tool for isolating and characterizing the structure of pectins, mainly those naturally occurring in tropical fruits.