Masters Theses

Ying Zheng

Date of Award

5-1991

Degree Type

Thesis

Degree Name

Master of Science

Major

Food Science and Technology

Major Professor

Sharon L. Melton

Committee Members

Marjorie P. Penfield, John R. Mount

Abstract

Fresh Tennessee-grown Cardinal strawberries, with and without calcium treatment (CAL) were stored In a permeable film (PFL) to water or a barrierfilm (BFL) for 0 to 8 days at 25°C or 0 to 20 days at 2°C. The percentage carbon dioxide and oxygen and ethylene (ppm) In the package headspace of the berries, percentage packages with off-flavor (OFF) and noticeable mold growth (MOLD), percentage weight unacceptable berries (UNACEPT), percentage weight loss (LOSS), percentage liquid drip (LIQ) and acidity (AC) and calcium content (Ca) on the berries were determined. The flavor of berries, with and without CAL, stored 0 to 8 days at 2° was evaluated by a sensory panel and their flavor volatiles were qualitated and quantitated by gas chromatography-mass spectrometry.

CAL of berries stored at 25°C reduced the rate of respiration as shown by decreased levels of carbon dioxide and ethylene In the package headspace of the berries at 4-days storage. CAL also reduced the MOLD In berries stored at the same temperature. However, CAL of berries stored at 2°C reversed these results. In addition, CAL which Involved treatment of the strawberries In a 0.5% calcium lactate solution for 4 min at 5 psi pressure Injured the berries. Strawberries with CAL had a greater LOSS and LIQ than berries without CAL, and the differences In LOSS and LIQ between berries with and without CAL were greater at 25°C than at 2°C storage. CAL has no effect on the AC of the berries but Increased the Ca content significantly. The flavor of the CAL berries was liked less than the flavor of the berries without CAL by the sensory panel, Twenty volatiles were identified and quantitated in the strawberries, and CAL resulted in decreased levels of several volatiles: ethyl butyrate, hexanal, 1-hexanol, hexyl acetate, linalool, 2-heptanol and 1-octanol.

Film did not have any great effect on the quality of the strawberries during storage, but storage of strawberries in the BFL resulted in a lower LOSS but a higher LIO than storage in the PFL, Storage in the BFL also resulted in higher carbon dioxide, but the level was not high enough to reduce the MOLD.

Generally, higher temperatures and longer storage times caused greater LOSS, LIQ, MOLD and OFF, The rate of increase in the levels of these variables was greater at 25°C than at 2°C. Levels of carbon dioxide and ethylene generally were maximum by 4 days storage at either temperature, with levels of these gases being higher at 25°C. AC decreased linearly across storage time at 2°C but increased quadratically at 25°C. Storage at 2°C for 8 days resulted in detectable levels of methyl isobutyrate, methyl butyrate, isobutyl acetate, ethyl methylbutyrate and ethyl hexanoate which were not detectable at 0 day, Storage, however, reduced the concentration of total volatiles.

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