Extraction, rheological and textural analyses and grading of pectin from stem pith of banana

Abstract

Introduction. Purpose of the work to identify suitable conditions for the extraction of pectin from stem pith of banana and to investigate how it affects rheological and textural properties of fruit jams. Materials and methods. Stem pith of local banana cultivar. Pectin extracted using hot water acidified with sulfuric acid. Yield was studied and expressed as percentage of dried raw material used. Degree of methylation was studied using titration method, monomeric composition was studied using high performance anion exchange chromatography with pulsed amperometric detector. Effect of banana pectin upon flow behavior and texture profile of the pineapple jam prepared with it was studied using rheometer. The pectin was graded using modified line spread method. Results and discussion. 27.91% of yield was obtained. All independent variables were found to affect the yield to varying degrees. Temperature and pH were found to be the most important conditions affecting yield, while time of heating and SLR (time of heating and solid to liquid ratio) were also found to be affecting the yield, but to a lesser extent. The highest of the yield was at a SLR of 50, pH of 1.5, temperature of 82°C and a time of heating of 52.5 minutes. Degree of methoxylation was found to be 62% with a composition similar to that of pectin from other sources reported by other workers. Banana pectin was found to be affecting the rheological and textural properties of pineapple jam. Yield stress of pineapple prepared using banana pectin was found to be 113 Pa, compared with 96 Pa for control. At the same time highest shear modulus for the test was 94 Pa, against a value of 60 Pa for the control. While banana pectin was found to be affecting the strength of pineapple jam, more of it was required to achieve it compared with citrus pectin. More force was required to make the jam flow, indicating a higher yield stress compared with citrus pectin. Textural properties of the jam were affected by the addition of banana pectin. Hardness was reduced from 6.18 for the control to 2.3 for the test while cohesiveness was reduced from 5.3 for control to 1.96 for test. At the time springiness was increased from 6.24 to 7.52. Grade banana pectin was found to be 90.9. Conclusions. Stem pith of banana is a potential alternate raw material for the extraction of pectin and the pectin so extracted is suitable to use as a gelling agent in food materials.