Date of Award

1991

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant, Environmental Management and Soil Sciences

First Advisor

David H. Picha

Abstract

Total and individual phenolic acids in firm-ripe fruit of ten different peach (Prunus persica Batsch.) genotypes were analyzed by spectrophotometry and high performance liquid schrmoatography (HPLC) and related to internal browning potential. A comparison of phenolic acid separation was made between five different column types. A Lichrosorb RP-18 column provided the best separation of the major phenolic acids in peach fruit mesocarp tissue. Quinic was the predominant phenolic acid, followed in concentration by gentisic, catechin, chlorogenic, and syringic acids. Quantities differed between genotypes. The genotypes with the highest internal browning potential contained the highest concentration of chlorogenic acid, gentisic acid, and total phenolics. Controlled atmosphere ((1% O$\sb2$, 4% O$\sb2$, 7% O$\sb2$, or 20% O$\sb2$) + 5% CO$\sb2$) (CA) storage was tested to determine its effect on several physical and chemical attributes of firm-ripe harvested fruit. The 1% O$\sb2$ + 5% CO$\sb2$ and 4% O$\sb2$ + 5% CO$\sb2$ stored fruit had lower concentrations of reducing sugars but higher sucrose than fruit stored in air. Fruit pH increased and titratable acidity decreased over the 40 day storage period. The 1% O$\sb2$ + 5% CO$\sb2$ and 4% O$\sb2$ + 5% CO$\sb2$ stored fruits were higher in citric and malic acid content than air stored fruit. Citric acid and malic acid decreased during storage. Little or no change in individual phenolic acids occurred during storage or between 1% O$\sb2$ + 5% CO$\sb2$ and air storage. Internal color darkened and became redder with storage. CA stored fruit were significantly firmer than air stored fruit. Sensory evaluation indicated CA (1% O$\sb2$ + 5% CO$\sb2$) stored fruit were more acidic, sweeter, and had better overall flavor than air stored fruit. Peach fruits held at room temperature for 2 days following storage at 0$\sp\circ$C in air for 40 days developed external and internal browning and fruit quality deteriorated. Comparable fruit stored at 0$\sp\circ$C under 1% O$\sb2$ + 5% CO$\sb2$ had very little internal breakdown and retained good quality after 2 days at 22$\sp\circ$C. The 20% O$\sb2$ + 5% CO$\sb2$ and air treatments had the highest percentage of fruit decay during storage at 0$\sp\circ$C.

Pages

106

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