Measurement of solids in tomato paste and the composition and properties of the soluble solids fraction

This thesis is an evaluation of two analytical procedures in the determination of total, soluble solids and insoluble solids in tomato paste. The microwave oven method was compared to the vacuum oven method. The vacuum oven method measures each solids fraction in the paste directly while the microwave method measures the total solids directly but employs an equation to calculate soluble and insoluble solids. The microwave method was faster and less labour intensive but gave small but significantly higher values for total (%) and insoluble solids (%) and lower values for soluble solids. These small differences although significant may not be important at the production level and therefore the microwave method is recommended for use by the industry. Additionally the soluble solids fraction showed to contain large amounts of lycopene-rich particles held in suspension. These particles were destabilized with pectinase treatment causing their precipitation. The presence of nitrogen in the soluble fraction and the loss of stability following pectinase treatment suggests that the particle is a pectin-polypeptide-lycopene complex.