Chlorophyll and green color stabilization on vegetable homogenates

• Author(s): Couto, Cristina Efimovna do
• Date: 2016
• Persistent ID: http://hdl.handle.net/10400.5/12924
• Origin: Repositório da UTL
• Subject(s): brocolli; color; lettuce; parsley; spinach
• Document Type: Master thesis
• Language: English
• Advisor(s): Almeida, Domingos Paulo Ferreira; Alegria, Maria João
• Contributor(s): Repositório da Universidade de Lisboa

Description

Mestrado em Engenharia Alimentar - Instituto Superior de Agronomia - UL

Several factors influence chlorophyll stability in foods and beverages. This study aims to determine the influence of raw material, heat treatment, pH and food additives on chlorophyll content and color stability of vegetable homogenates. Fully expanded spinach, parsley, broccoli, and lettuce leaves were harvested and immediately processed. Leaf (10%) homogenates were bottled, heat-treated at 90 ºC for 60s, cooled and stored at 20 ºC. Chlorophylls a and b were measured before and after pasteurization, and during shelf-life. Color was assessed with a colorimeter. Broccoli and parsley, spinach and lettuce had an initial hue angles of 132.8°, 129.0° and 109.8°, respectively. Chlorophyll content was higher in broccoli (171.4 μg mL-1) and lower in lettuce (44.4 μg mL-1). Hue and chlorophyll content decreased in all homogenates during pasteurization. At pH 8.5 the addition of sodium bicarbonate and zinc chloride had a positive effect on retention of chlorophyll and hue of spinach, parsley and broccoli homogenates, with hue increases of 8% in samples treated with sodium bicarbonate and 9% in those with zinc chloride. At pH 4.5 hue decreased 18% in all samples, with accompanying color shift to olive green. During shelf-life, hue and chlorophyll content was better maintained at higher pH in all samples, with higher values registered for broccoli samples, irrespective of additive. Pre-harvest zinc application in lettuce had a positive effect on color of pasteurized samples, with no significant effect in chlorophyll content. However, there was visual evidence of color retention for these samples. Total chlorophylls decreased 19% in all lettuce samples due to heat treatment. While hue, chlorophyll content and visual color were better maintained in samples with pre-harvest treatments during shelflife, the addition of zinc did not affect these parameters. A significant relationship between sample hue and total chlorophyll content was found, for all vegetable samples in study