Physiological bases for texture and color changes in fresh-cut ´Rocha´ pear and melon: implications on development of products and processes

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Volatile and quality changes in fresh-cut cantaloupe and honeydew melons stored in modified atmosphere packaging

Publication . Amaro, Ana L.; Beaulieu, John C.; Stein, Rebecca E.; Almeida, Domingos P. F.; Nunes, Carla

Modified atmosphere packaging (MAP) in fresh-cut melons has been reported to preserve the visual quality during storage, yet its effect upon aroma and firmness is cultivar-dependent. The main objective of this research was to compare the properties of fresh-cut from a fast senescing cantaloupe with a slow senescing honeydew melon, regarding changes in quality and volatiles, when stored in passive MAP. Freshcut cubes of cantaloupe and honeydew melons were packaged in polypropylene trays, over-wrapped with a microperforated film and stored for 14 days at 5 ºC. Three replicate packages of each cultivar were assayed at day 0, 4, 7, 11 and 14 for color, firmness, soluble solid content (SSC), respiration rate and volatile retention, and the experiment was repeated. Volatile compounds were extracted using a relatively recent technique, Stir Bar Sorptive Extraction (SBSE), and quantified via GC-MS. Color and SSC remained constant throughout storage. During the first 4 days of storage, the cantaloupe cubes softened at a higher rate (2.0 N day-1) than honeydew cubes (0.9 N day-1), but firmness remained relatively unchanged thereafter until the end of the storage period. Fresh-cut cantaloupe cubes exhibited a higher respiration rate (17.5-43.4 mL CO2 kg-1 h-1) than fresh-cut honeydew cubes (7.7–30.0 mL CO2 kg-1 h-1), throughout the entire storage period. Esters and aldehydes were the major volatile compounds present in the samples of both cultivars, but cantaloupe yielded higher concentrations of esters and aldehydes, and lower concentrations of alcohols than honeydew. Esters increased their levels during storage, whereas alcohols and aldehydes decreased.

2010Book part

Open access

Physiological bases for texture and color changes in fresh-cut ‘rocha’ pear: implications for the development of products and processes

Publication . Gomes, Maria Helena; Almeida, Domingos P. F.; Nunes, Carla

The physiological bases for the effectiveness of technologies used in fresh-cut fruit were examined in an attempt to foster the shift from a market-pull to a science-push innovation model. Respiration rate of fresh-cut ‘Rocha’ pear were measured at various oxygen concentrations. Apparent Km values for oxygen uptake were very close to the fermentation thresholds, indicating that it is physiologically impossible to reduce the respiration rate of fresh-cut pear by more than 50% without inducing fermentation. Based on this information, we hypothesize that optimizing oxygen concentration inside packages is of little or no value in fresh-cut pears. Additionally, additives used to reduce enzymic browning and softening may have pleiotropic effects on quality. It was found that pH significantly affected the rate and intensity of browning of fresh-cut pears. Browning was more intense in pears treated at pH 3.0 and less pronounced at pH 7.0, but the softening rate was lower at the latter pH value. Calcium salts also affected texture and color in a salt-specific manner. Larger color changes were observed with propionate and lactate. Although calcium ascorbate reduced color changes, fruit slices treated with this salt were softer than those treated with calcium propionate, lactate or chloride. Based on the physiological information gathered, we will develop and evaluate an integrated process to maximize the quality of fresh-cut ‘Rocha’ pear throughout the distribution chain.

2010Book part

Open access