Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: Postharvest Sensory, Processing and Packaging of Catfish

Location: Food Processing and Sensory Quality Research

2013 Annual Report


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:
Improvements have been made using ultra performance liquid chromatography for the rapid determination of anthocyanidins from blueberries. Raw blueberries, press cakes, and clarified and non-clarified juice samples were hydrolyzed and analyzed for anthocyanidins. The press cake had the greatest amounts of anthocyanidins, while the ultrafiltered juice prepared in the pilot plant contained the least. In another study, conjugated anthocyanins from blueberries are being evaluated by liquid chromatography-mass spectrometry-mass spectrometry (LC-MS-MS) in order to understand changes that occur during juice processing. There were five common anthocyanidins conjugated to glucose, galactose, and arabinose in blueberries. In addition, there were a large number of compounds in the juice not previously reported. Detecting and identifying the conversions of monomeric to polymeric polyphenolic products, will be used in understanding the bioavailability and other properties of these compounds, and how this changed during processing.

In fresh squeezed blueberry juice studies, a trained sensory panel evaluated the correlations between blueberry juice components and concentrations with descriptive flavor attributes. As expected, glucose, fructose, and total sugars correlated with sweet taste. Sour taste correlated with total acids, but not with individual acids; however, none of the polyphenols correlated with astringent mouthfeel. In another study, the gas chromotograpy-olfactometry (GC-O) was used to assess the volatiles of two different blueberry types, southern highbuch and rabbiteye. A positive correlation of cis-3-hexen-1-ol and the blueberry sensory score was observed. The volatile profiles of five Louisiana-grown rabbiteye cultivars were assayed at four maturities. Fifty-three volatile compounds were recovered, of which ten compounds were recovered for the first time in blueberry. There were significant differences within cultivars and maturities.

The volatile profile in freshly-prepared pomegranate juices were investigated using a microextraction procedure. There were marked differences between “endogenous” volatiles extracted in the not-from-concentrate pilot plant juices, versus the suite of compounds recovered in various processed commercial juices. In another study, the Methyl Cellulose Precipitable Tannin Assay method was modified to be used on processed pomegranate juice to measure astringency. This test, along with °soluble solids, pH, and an ‘electronic tongue’ instrument, was evaluated for the utility to evaluate commercial pomegranate juices. The Methyl Cellulose Precipitable Tannin Assay method moderately correlated with astringent mouthfeel. None of the seven electronic tongue sensors correlated with any of the sensory taste attributes.


4.Accomplishments
1. Improved method of determining anthocyanidins in blueberries and pomegranates. Researchers at the Agricultural Research Service, New Orleans, Louisiana developed an ultra performance liquid chromatography method for the rapid determination of anthocyanidins from blueberries and pomegranates. Using acid hydrolysis under nitrogen on the sugar-conjugated anthocyanins, the method was perfected to rapidly resolve all the anthocyanidins found in these crops. They attained resolution and efficiency superior to current methods. This method will facilitate rapid, reliable and quantitative analysis, of anthocyanidins which can readily be tracked through processing and metabolic.

2. Correlations of sugars, acids and polyphenolics with descriptive flavor attributes in blueberry juices. Working with fresh squeezed blueberry juices, researchers at the Southern Regional Research Center (SRRC), New Orleans, Louisiana, investigated the association between concentrations of sugars, acids and polyphenolics with descriptive flavor attributes. Sucrose was negatively correlated with sweet taste, indicating the breakdown of sucrose into fructose and glucose during juice processing and quinic acid and total acids were negatively correlated with sweet taste. Bitter taste was negatively correlated with delphinidin, cyanidin, petunidin and peonidin, which indicates that these anthocyanidins did not seriously contribute to bitter taste in fresh blueberry juice. Astringent mouthfeel correlated with malic acid and total acids. These associations are useful for researchers to gauge the likely effects processing and storage have regarding acceptable and unacceptable aroma and flavor attributes in juices.

3. Creation of a volatile database from locally grown rabbiteye blueberries. Researchers at the Agricultural Research Service, New Orleans, Louisiana, investigated the aroma, astringency and flavor of rabbiteye blueberries, commonly grown in the Southeast. Volatile profiles were obtained from five Louisiana-grown rabbiteye cultivars at four maturities. Ten compounds were recovered for the first time in blueberry. Terpenoids and linalools were the most significant volatile classes, followed closely by esters, aldehydes then alcohols. This data is being used to evaluate changes in rabbiteye blueberry aroma, astringency, and flavor during berry processing.

4. Evaluation of conjugated anthocyanin in blueberries. Conjugated anthocyanins from blueberries were evaluated by liquid chromatography-mass spectrometry-mass spectrometry by researchers at the Agricultural Research Service, New Orleans, Louisiana. There is no database that contains the several hundred glycosylated and aceyleted anthocyanins (polymers) that are thought to be present. The five common anthocyanidins of blueberry are conjugated to glucose, galactose and arabinose, and in addition, there are a large number of unidentified compounds in the juices. The project is providing a database that can be used to monitor changes that occur during juice processing and in value-added byproducts derived from the spent press cake. In addition, detecting and identifying monomeric to polymeric polyphenolic changes that occur during processing and storage will aid in determining the in vivo fate and bioavailability of these compounds.


Review Publications
Bett Garber, K.L., Lea, J.M. 2013. Development of flavor lexicon for fresh pressed and processed blueberry juice. Journal of Sensory Studies. 28:161-170.

Amaro, A., Fundo, J., Oliveira, A., Beaulieu, J.C., Fernandez-Truxillo, J., Almeida, D. 2013. 1-Methylcyclopropene effects on temporal changes of aroma volatiles and phytochemicals of fresh-cut cantaloupe. Journal of Food Science and Technology. 93(4):828-837.

Perkins-Veazle, P., Beaulieu, J.C., Siddiq, M. 2012. Watermelon, cantaloupe, and honeydew. Subtropical and Tropical Agriculture. 549-568.

Last Modified: 10/21/2014
Footer Content Back to Top of Page