Color and flavor stability of strained carrots as affected by genotype and processing

Abstract

Strained carrot quality is impacted by color degradation and flavor changes. Maceration, followed by heating in open holding tanks may cause chemical changes that lead to brown color formation. Processing carrots in low oxygen environments may result in better color and flavor retention after processing and during storage. The objective of this study was to evaluate mechanisms for loss of strained carrot quality and to determine chemical attributes responsible for improved carrot color and flavor. Chemical and sensory attributes were evaluated for ten genotypes. Additional thermal processing treatments included a control (21%02) nitrogen (N2) sparge, blanch/freeze/nitrogen sparge (BFN2), oxygen (02) sparge and glucose oxidase-catalase (GOC). Samples were stored for various times and temperatures and monitored periodically for chemical and sensory attributes. Changes in color, soluble phenolics, carotenoids, molecular weight, sugars and pH were measured during storage. Sensory attributes were monitored in samples spiked with various concentrations of 6-methoxymellein (6-NM) to determine how this stress induced metabolite affects carrot quality. Phenolic polymerization due to autoxidation was associated with color loss in strained carrots. Declines in pH, soluble phenolics and total carotenoids all correlated with decreased chroma values. Significant losses in color, phenolics and carotenoids were found in the control and O2 sparged samples compared to N2 sparged and BFN2 samples. Molecular weight of phenolic compounds was lower in nitrogen sparged samples than oxygen sparged samples. Sucrose values were slightly higher in BFN2 and N2 sparged samples while changes in glucose and fructose were not significant. Oxygen control strategies improved overall color of strained carrots. Genotypic evaluation indicated that pre-harvest stress induced formation of phytoalexins was detrimental to sensory quality. Addition of the phytoalexin 6-@ to commercial strained carrots resulted in a just noticeable difference at 48.4-71.0 ppm, a 93.7 ppm recognition threshold and a terminal threshold at >180 ppm for bitterness. Food processors should be concerned with growing and postharvest handling conditions that promote 6-@ formation and oxidative deteriorative reactions that result in reduced strained carrot quality.