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  • Author or Editor: Betty Hess x
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Elevated CO2 atmospheres reduce decay and extend postharvest life based on appearance of strawberries but flavor quality may be lost faster than appearance quality. California-grown `Aromas', `Diamante,' and `Selva' strawberries were stored at 5 °C in air or 20 kPa CO2 + air for 15 days and evaluated for quality attributes, chemical changes, and flavor. In a “Preference Test”, `Selva” and `Diamante' were more preferred than `Aromas'. This may be related to their higher titratable acidity (TA), total soluble solids (TSS), the concentration of total aroma compounds, a different methyl/ethyl esters ratio, and the presence of C6 aldehydes. The postharvest life in air was 7, 9, and 9 days for `Aromas', `Diamante' and `Selva', respectively and these periods were extended by 30%, 20%, and 45% in the CO2-enriched atmosphere. There were no significant differences in TA or TSS between fruits kept in air or in air + CO2 and panelists could not detect differences in sourness and sweetness after 9 days of storage. In contrast, there was a trend for CO2-stored fruits of the three cultivars to be categorized as more aromatic, and for `Aromas' and `Selva' fruits to be described as more “strawberry like” in flavor compared to the corresponding air-stored fruits. The total aroma concentration decreased to a lesser extent in `Aromas' and `Selva' strawberries kept in air + CO2 than in those stored in air. The CO2-enriched atmosphere stimulated fermentative metabolism only in `Aromas' and `Selva'; the higher concentration of ethanol in these two cultivars favored the synthesis of ethyl esters. The total content of aroma compounds and the methyl/ethyl esters ratio may be two of the multiple factors determining the overall fruit flavor.

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`Shinko' and `Shinsui' Asian pears were kept in air, 2 kPa O2, 2 kPa O2 + 2.5 kPa CO2, and 2 kPa O2 + 5 kPa CO2 (balance N2 in each treatment) at 0 °C or 5 °C for up to 24 weeks. The three CA treatments reduced respiration (O2 consumption) and ethylene production rates relative to air control pears; these rates were higher at 5 °C than at 0 °C and higher for `Shinsui' than for `Shinko' pears. While `Shinsui' pears had a climacteric pattern of respiration and ethylene production rates, `Shinko' pears produced very small quantities of ethylene and exhibited a non-climacteric respiratory pattern. `Shinko' pears had a much longer postharvest life than `Shinsui' pears (24 weeks vs. 12 weeks at 0 °C). CA treatments had a greater effect on delaying deterioration of `Shinsui' than `Shinko' pears, which were more sensitive to CO2 injury and associated accumulation of fermentative metabolites (acetaldehyde, ethanol, ethyl acetate). `Shinko' pears did not benefit from CA storage and were best kept in air at 0 °C. An atmosphere of 2 kPa O2 with or without up to 5 kPa CO2 delayed flesh breakdown of `Shinsui' pears during storage 0 °C.

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The variation in chilling sensitivity of mature-green specialty bananas (Musa paradisiaca var. sapientum) and plantains (Musa paradisiaca var. paradisiaca) was examined using four cultivars of bananas and one plantain cultivar stored under various time and temperature combinations. Cold storage for 1 day at 5.0, 7.2, or 10.0 °C (41, 45, or 50 °F) resulted in acceptable fruit quality for up to 8 days at 20.0 °C (68 °F) for `Petite' and `Red Macabu' bananas and `Dominico Harton' plantains. `Grand Nain' and `Yangambi' bananas were considered unmarketable due to moderate to severe graying after 8 days at 20.0 °C when fruit were previously stored for 1 day at 5.0 or 7.2 °C. Storage for 3 days at 10.0 °C was acceptable for all cultivars tested, however 5 days at 10.0 °C resulted in moderate to severe browning and graying of the `Grand Nain' fruit. The traditional Cavendish-type, `Grand Nain', as well as `Petite' and `Yangambi', required temperatures greater than 10.0 °C for a 7-day storage duration while `Red Macabu' bananas could be safely stored for 7 days at 10.0 °C. Plantains could be stored at 7.2 °C for 7 days without visible chilling injury symptoms. The storage of specialty bananas and plantains at or above their minimum safe temperatures resulted in improved uniformity of ripening and overall quality of the fruit due to a decrease in chilling injury symptoms.

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Abstract

Preharvest treatment with 400 ppm aminoethoxyvinylglycine (AVG) delayed the ripening of ‘Bartlett’ pears kept at 20°C. The effect was not uniform, with the delay in ripening ranging from a few to 112 days. Prolonged storage at 20° was accompanied by a relatively steady, low level of respiration, gradual degreening, and partial suppression of the eventual climacteric. The combined effect of AVG treatment and prolonged ‘nonripening’ storage at 20° led to a marked attentuation of the production of 4 readily measurable volatiles including methyl-, ethyl-, and hexylacetate as identified by cochromatography and combined gas chromatography–mass spectrometry. Surprisingly, prolonged storage resulted in a much increased production of 2 other volatile fractions when AVG inhibition was reversed by C2H4 treatment. The emanation of all measured volatiles was closely coincident with the climacteric peak. These observations confirm prior reports of disuniform effects of preharvest AVG treatment and reveal that metabolic transitions during prolonged, nonripening storage may have adverse effects on fruit quality.

Open Access

`Hass' avocado (Persea americana Mill.) fruit were kept in air, 0.25% O2 (balance N2), 20 % O2 + 80% CO2, or 0.25% O2 + 80% CO2 (balance N2) at 20C for up to 3 days to study the regulation of fermentative metabolism. The 0.25% 02 and 0.25% 02 + 80% CO2 treatments caused accumulations of acetaldehyde and ethanol and increased NADH concentration, but decreased NAD level. The 20% O2 + 80% CO2 treatment slightly increased acetaldehyde and ethanol concentrations without significant effects on NADH and NAD levels. Lactate accumulated in avocadoes kept in 0.25 % 02. The 80% CO, (added to 0.25% O2) did not increase lactate concentration and negated the 0.25% O2-induced lactate accumulation. Activities of PDC and LDH were slightly enhanced and a new isozyme of ADH was induced by 0.25% O2, 20% O2 + 80% CO2, or 0.25 % O2 + 80% CO2; these treatments partly reduced the overall activity of the PDH complex. Fermentative metabolism can be regulated by changes in levels of PDC, ADH, LDH, and PDH enzymes and/or by metabolic control of the functions of these enzymes through changes in pH, ATP, pyruvate, acetaldehyde, NADH, or NAD. Chemical names used: alcohol dehydrogenase (ADH), adenosine triphosphate (ATP), lactate dehydrogenase (LDH), nicotinamide adenine dinucleotide (NAD), reduced NAD (NADH), pyruvate decarboxylase (PDC), pyruvate dehydrogenase (PDH).

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