Extraction temperature alters phytochemical concentrations and uality of mayhaw juice

Document Type

Conference Proceeding

Publication Date

12-12-2003

Abstract

Research has demonstrated that antioxidants contained in fruit can provide protection against certain human degenerative conditions that are associated with oxygen free radical damage. An increasing public awareness of the benefits of antioxidants necessitates the determination of optimum processing practices for extracting juice with minimal loss in quality. Fruit of 'Royal Star' and 'Texas Star' mayhaws were collected from plots at the Calhoun Research Station in Calhoun, Louisiana, in May and frozen at-60 °C. Fruit were thawed overnight at 2 °C and incubated for one hour at 2, 20, 40, 60, 80, and 100 °C prior to hand-pressing to extract the juice. Titratable acidity, soluble solids (%), and pH were determined on freshly pressed juice. Juice was assayed for total phenolics, anthocyanins, and antioxidants. Antioxidant activity was determined using the Ferric Reducing/ Antioxidant Power (FRAP) assay. Increasing temperature from 2 to 100 °C had no significant effect on juice pH of 'Texas Star' but reduced the pH of 'Royal Star'. Titratable acidity was variable in response to increasing temperature, with the two cultivars responding differently: 'Royal Star' peaked at 60 °C and 'Texas Star' at 100 °C. Total phenolics and FRAP increased from 2 °C to 60 °C, peaking at 60 °C, but then declined at 80 °C before spiking upward again at 100 °C (possibly due to breakdown of structural components). Anthocyanin content responded quadratically, peaking at 60 °C. 'Royal Star' juice contained significantly higher levels of anthocyanins and phenolics, and had a higher antioxidant capacity than 'Texas Star' juice. FRAP antioxidant activity was more closely correlated with total phenolics (r2=0.98) than anthocyanin content (r2=0.79).

Publication Source (Journal or Book title)

Acta Horticulturae

First Page

823

Last Page

828

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