Tomato attributes and their correlation to peelability and product yield

Although tomato paste research has received significant attention, relatively little effort has been addressed to optimization of value-added whole peel and diced tomato processing. Our laboratory has conducted research evaluating tomato attributes which may be indices of peelability and product yield. Eleven tomato varieties were harvested at USDA stage 4 (pink), USDA stage 6 (red) and red plus either 1, 2 or 3 weeks time. Maturity was established by tagging either flowers or pink fruit. Fruit was evaluated for physical attributes, texture, paste quality, peelability and product yield. Physical attributes measured included color, density, height, weight, width, shoulder height, stem scar diameter, locule number and gel state, seed number and weight, pericarp wall thickness and red layer thickness. Paste quality was determined using a microwave hot break procedure and evaluation of raw and cooked color, Bostwick, pH, degreesBrix, titratable acidity and serum viscosity. Tomatoes were exposed to steam, vacuum and mechanical peel eliminators and then percent peelability and product yield were calculated. Firmness of raw and peeled diced tomatoes was measured using a Kramer shear cell. Discriminant analysis was used to determine which subsets of physical attributes correlated to desirable levels of peelability and product yield. A model equation was developed using four physical attributes, e.g. width, stem scar diameter, pericarp, thickness and red layer thickness. Use of the model allowed for prediction of "paste" vs. "whole peel/dice" group allocation with 90% accuracy in pilot scale studies. The model is currently being tested at the commercial scale with California processors.