1a. Objectives (from AD-416):
Objective 1: Determine the correlative relationships between chemical composition and descriptive sensory scores to establish the levels of polyphenols (flavonoids, tannins, lignins, anthocyanins) relative to key flavor and taste compounds in model fruit juices that result in low to high ratings for astringency, bitterness, and other undesirable flavor attributes. Objective 2: Determine the effects of processing technologies on relative amounts of polyphenolic and key flavor compounds and resulting impact on the sensory profiles for juices, concentrates, and puree/fruit smoothie type products. Objective 3: Using the results of Objectives 1 and 2, develop means (e.g. complexation, masking, concentration, blending, buffering agents, encapsulating agents) to amplify positive flavor attributes and decrease astringency and bitter flavors in juices/beverages prepared from phytonutrient-rich fruits without adversely affecting phytonutrient content, solubility, stability, or phytonutrient bioavailability.
1b. Approach (from AD-416):
In Objective 1, baseline benchmarks will be established for high to low levels of sensory attributes in regards to total and selected monomeric and polymeric polyphenol content in single-strength blueberry and pomegranate juices prepared from commercial concentrates that have been diluted to Code of Federal Regulations (CFR) minimum and/or commercial °Brix standards. Flavor intensities will be related to the concentrations of polyphenol compounds, sugars, acids, and key flavor compounds. In Objective 2, changes in °Brix, acidity, color, total phenolic and key polyphenolic compound contents, antioxidant capacity, and sensory profiles of model, single-strength blueberry and pomegranate juices will be assessed at the juice processing stages (control points). Processing conditions will be altered at stages to improve the flavor profiles of juices, purées, and functional beverages without adversely affecting phytonutrient content, solubility, stability, or bioavailability. In Objective 3, further optimization of flavor and phytonutrient content/bioavailability will be achieved by incorporating into the processing scheme, novel physical and chemical means, and via varietal selection and blending.
3. Progress Report:
California-grown pomegranate cultivars were selected from the Agricultural Research Service (ARS) germplasm repository to represent high versus low quality characteristics. Aroma volatiles were analyzed in freshly pressed juices from several cultivars. Based upon color, ellagic acid content, and bitterness/astringency, several cultivars are not suitable for juice; however, they served to deliver sensory and analytical databases to calibrate future experiments. Several locally grown blueberry varieties and California pomegranate cultivars were analyzed by gas chromatograph-mass spectrometry to determine their volatile profiles. We have identified substantially different volatile profiles between southern highbush and rabbiteye blueberry types. Differences positively correlated with desirable sensory attributes may guide variety selection for juice production. Not-from-concentrate pomegranate juice was prepared by hydraulic pressing, ultra-filtration, and pasteurization. Processing stages were used to compare compositional and quality differences. Juice stability during storage was also evaluated. Volatile compounds have been identified in these juices. Juices from whole pressed fruit, ultra-filtration, and in-house pasteurization had very similar volatile profiles, with 32 compounds recovered; however, commercial concentrates and our own in-house ARS concentrate had only nine compounds. Loss of several flavor/aroma compounds occurred in commercial concentrates compared against freshly produced, not-from concentrate juices. Differences in the recovery and quality of blueberry juice with different processing regimes were studied in selected varieties of rabbiteye and southern highbush blueberries. Fruit was pressed immediately after harvest/freezing, and by making a mash with heat and heat plus commercial pectinase enzymes. Commercial pectinases used in heated mashes ameliorated gelling and increased percentage juice recovery. Several local rabbiteye and southern highbush blueberry varieties were harvested twice during the season and stored frozen to evaluate quality and chemical differences in hand-pressed juice. Blueberry juice, pomace, and skins were analyzed for polyphenolics, anthocyanins, anthocyanidins, oxygen radical absorbance capacity, and total phenolics. A detailed gas chromatography-olfactometry-mass spectrometry appraisal is under way to differentiate blueberry types for volatiles and human described aroma attributes.
Amaro, A.L., Beaulieu, J.C., Grimm, C.C., Stein, R.E., Almeida, D.P. 2011. Effect of oxygen on aroma volatiles and quality of fresh-cut cantaloupe and honeydew melons. Food Chemistry. 130(1):49-57.