Stability of copigmented anthocyanins and ascorbic acid in muscadine grape juice processed by high hydrostatic pressure

Intermolecular copigmentation is one of the mechanisms of stabilization of anthocyanins in nature and is also responsible for the characteristic color and stability of aged red wines. In the present study, the effect of polyphenol oxidase (PPO) activity on phytochemical stability of an ascorbic acid-fortified muscadine grape juice following high hydrostatic pressure (HHP) processing (400 and 550 MPa for 15 min) and after 21 d of storage at 25 degrees C was investigated. Addition of rosemary and thyme polyphenolic extracts (copigmentation) was evaluated as a means to stabilize anthocyanins and ascorbic acid during pressurization and subsequent storage. Polyphenolic extracts were partially purified in order to reduce their content of PPO substrates, and improve their stabilization properties within juice matrix. Overall PPO activity increased (3- and 2.5-fold) following HHP at 400 and 550 MPa, respectively, although it was significantly lower in copigmented treatments. Higher anthocyanin losses occurred at 400 (approximately 70%) than at 550 MPa (approximately 46%), which were correlated to antioxidant losses (r = 0.89). Similarly, greater ascorbic acid losses were observed at 400 (84%) than at 550 MPa (18%). Copigmentation increased anthocyanin retention in reference to pressurized controls (3- and 3.2-fold for rosemary and thyme treatments, respectively) and decreased ascorbic degradation (20 to 32%). In stored samples, higher anthocyanin content (>2-fold) and antioxidant capacity (>1.5-fold) was observed for copigmented treatments when compared to control juices. Addition of partially purified copigments increased muscadine grape juice color, antioxidant activity and also reduced phytochemical losses during HHP processing and storage.

Contribution of periderm material and blanching time to the quality of pasteurized peach puree

Fresh peaches were blanched for either a long (20 min) or short (2 min) time, with and without periderm material. Samples were then macerated into purees and pasteurized in boiling water for 30 min. Samples were subsequently stored at 40 degrees C for 4 weeks to determine physicochemical and sensory changes affecting overall quality and nutritional content. Purees containing periderm had higher antioxidant activity (AOX) and individual phenolic acid content after processing and storage, with good correlation to AOX observed with chlorogenic acid (r = 0.82). Long blanch times resulted in increased levels of extraction and retention of both total soluble phenolics and ascorbic acid. Quantitative descriptive analysis demonstrated increased aromatic perception of skin in samples containing periderm material, but the remaining sensory attributes were indistinguishable between treatments. Macerating peaches without periderm removal was demonstrated to increase levels of bioactive phytochemicals and increase the processing yield by 7. 6%, without significantly impacting product quality, color, or sensory attributes.

Changes in phytochemical and antioxidant activity of selected pepper cultivars (Capsicum species) as influenced by maturity

The effect of fruit maturation on changes in carotenoids, flavonoids, total soluble reducing equivalents, phenolic acids, ascorbic acid, and antioxidant activity (AOX) in different pepper types (Capsicum annuum, Capsicum frutescens, and Capsicum chinese) was determined. Generally, the concentration of these chemical constituents increased as the peppers reached maturity. Peppers contained high levels of L-ascorbic acid and carotenoids at maturity, contributing 124-338% of the RDA for vitamin C and 0.33-336 RE/100 g of provitamin A activity, respectively. Levels of phenolic acids, capxanthin, and zeaxanthin generally increased during maturation, whereas the level of lutein declined. Flavonoid concentrations varied greatly among the pepper types analyzed and were negatively correlated to AOX under the conditions of the beta-carotene-linoleic assay. Model systems were used to aid in understanding the relationship between flavonoids and AOX. Significant increases in AOX were observed in pepper juice models in response to increasing dilution factors and the presence of EDTA, indicating a pro-oxidant effect due to metal ions in the system. In vitro models demonstrated that increasing levels of flavonoids in combination with constant levels of caffeic and ascorbic acid gave a resultant AOX that was either additive of the two compounds or competitive in their ability to scavenge peroxyl radicals. The model systems were in good agreement with the chemical composition of the pepper cultivars and reflected the interactions affecting AOX. More research is needed to understand the complex interactions that occur among various antioxidants present in pepper extracts.

Antioxidant changes and sensory properties of carrot puree processed with and without periderm tissue

Carrot purees were thermally processed with and without the periderm tissue after a long and short blanch time, with and without vacuum deaeration treatments. Samples were stored at an elevated temperature (40 degrees C for 4 weeks) to determine physicochemical changes affecting antioxidant activity (AOX), as measured by the coupled oxidation of beta-carotene and linoleic acid assay, and overall quality characteristics. Differences in AOX between treatments before thermal processing and during storage were associated with increased levels of phenolic acids and the subsequent development of numerous compounds thought to be oxidation products of phenolic acids. Samples processed with periderm tissue contained higher levels of phenolic acids, total carotenoids, and sugars than samples processed without periderm tissue. Strained carrot color was adversely affected by a long blanch time compared to a short blanch in treatments with and without periderm tissue, indicating improved color with reduced preprocessing heating. Sensory analyses by a quantitative descriptive analysis panel indicated increased musty/moldy and terpene flavors in samples processed with periderm tissue that were seemingly related to elevated levels of phenolic acids and volatile terpenoids. Terpenoid levels were reduced with deaeration steps prior to thermal processing. Processing carrots without removal of periderm tissue has proven to be a viable option when short blanch times and deaeration steps are employed.