Cindi Brownmiller

Influence of extrusion processing on procyanidin composition and total anthocyanin contents of blueberry pomace.

Blueberry juice processing by-products are a rich source of procyanidins, which comprise a group of compounds shown to possess numerous health benefits, including protection against coronary heart disease, type II diabetes, and obesity. Most of the procyanidins present in blueberry pomace, however, are large molecular weight compounds that are poorly absorbed and show weak bioactivity compared to the smaller molecular weight monomers and dimers. The objective of our study was to identify optimal extrusion variables to enhance the contents of monomers and dimers at the expense of large molecular weight procyanidin oligomers and polymers. Extrusion variables temperature (160 and 180 degrees C) and screw speed (150 and 200 rpm) were tested using mixtures of blueberry pomace with decorticated white sorghum flour at a ratio of 30 : 70 and 45% moisture content. Extrudates were analyzed for procyanidin composition and total anthocyanin content. Extrusion of blueberry pomace increased the monomer, dimer, and trimer contents considerably at both temperature and screw speeds. The highest monomer content, obtained at 180 degrees C and 150 rpm screw speed, was 84% higher than the nonextruded control. Significantly higher levels of dimer and trimer contents were also obtained under these conditions. Increases in monomer, dimer, and trimer contents apparently were the result of reduced polymer contents, which was approximately 40% lower for samples extruded at 180 degrees C temperature and 150 rpm screw speed. Extrusion processing reduced total anthocyanin contents by 33% to 42% indicating that additional treatments are needed to retain the pigments. These results demonstrate that extrusion processing can be used to increase procyanidin monomer and dimers in blueberry pomace.

Jam Processing and Storage Effects on Blueberry Polyphenolics and Antioxidant Capacity

Fresh blueberries were processed into sugar and sugar-free jams and stored for 6 months at 4 and 25 degrees C. The jams were analyzed immediately after processing and over 6 months of storage for polyphenolic content, percent polymeric color, and antioxidant capacity. Processing resulted in losses of anthocyanins, procyanidins, chlorogenic acid, and ORAC in both jam types, but flavonols were well retained. Marked losses of anthocyanins and procyanidins occurred over 6 months of storage and were accompanied by increased polymeric color values. Chlorogenic acid levels also declined during storage, but flavonols and ORAC changed little. Jams stored at 4 degrees C retained higher levels of anthocyanins, procyanidins, and ORAC and had lower polymeric color values than jams stored at 25 degrees C. Sugar-free jams retained higher levels of anthocyanins and had lower polymeric color values than sugar jams late during storage. Blueberry jams should be refrigerated to better retain polyphenolics and antioxidant capacity.

Processing and Storage Effects on Procyanidin Composition and Concentration of Processed Blueberry Products

Blueberries are a rich source of procyanidins that may contribute to the reduced risk of chronic disease; however, because of seasonal availability, the berries are commonly consumed in thermally processed forms after long-term storage. In this study, we evaluated the effects of processing and 6 months of storage on procyanidin composition and content of blueberries that were canned in syrup (CS), canned in water (CW), pureed, and juiced (nonclarified and clarified). Processing blueberries into various forms resulted in significant losses of total procyanidins, with only 19 and 23% being retained in nonclarified and clarified juices, 41% retained in purees, and 65 and 78% being retained in berries CS and CW. The mono- and dimers were retained to a much greater extent than larger oligomers in all products following processing. Procyanidins were further degraded during 6 months of storage, with only 8% and 11% retained in clarified and nonclarified juices, 7% retained in pureed, and 22 and 32% retained in berries CS and CW. Similar to results obtained following processing, mono- and dimers were better retained than larger oligomers. Methods are needed to prevent procyanidin losses during processing and storage.

Improved stability of chokeberry juice anthocyanins by β-cyclodextrin addition and refrigeration.

Chokeberry anthocyanins are susceptible to degradation during processing and storage of processed products. This study determined the effects of three pH levels (2.8, 3.2, and 3.6) and four β-cyclodextrin (BCD) concentrations (0, 0.5, 1, and 3%) alone and in combination on the stability of chokeberry juice anthocyanins before and after pasteurization and over 8 months of storage at 4 and 25 °C. Lowering the pH from 3.6 to 2.8 in the absence of BCD provided marginal protection against anthocyanin losses during processing and storage. Addition of 3% BCD at the natural chokeberry pH of 3.6 resulted in excellent protection of anthocyanins, with 81 and 95% retentions after 8 months of storage at 25 and 4 °C, respectively. The protective effect of BCD was lessened with concentrations <3% and reduction in pH, indicating changes in anthocyanin structure play an important role in BCD stabilization of anthocyanins.

Changes in Chokeberry (Aronia melanocarpa L.) Polyphenols during Juice Processing and Storage

Chokeberries are an excellent source of polyphenols, but their fate during juice processing and storage is unknown. The stability of anthocyanins, total proanthocyanidins, hydroxycinnamic acids, and flavonols at various stages of juice processing and over 6 months of storage at 25 °C was determined. Flavonols, total proanthocyanidins, and hydroxycinnamic acids were retained in the juice to a greater extent than anthocyanins, with losses mostly due to removal of seeds and skins following pressing. Anthocyanins were extensively degraded by thermal treatments during which time levels of protocatechuic acid and phloroglucinaldehyde increased, and additional losses occurred following pressing. Flavonols, total proanthocyanidins, and hydroxycinnamic acids were well retained in juices stored for 6 months at 25 °C, whereas anthocyanins declined linearly. Anthocyanin losses during storage were paralleled by increased polymeric color values, indicating that the small amounts of anthocyanins remaining were present in large part in polymeric forms.

Improved color and anthocyanin retention in strawberry puree by oxygen exclusion

BACKGROUND: Strawberry puree color is unstable during processing and storage due to oxidative reactions. OBJECTIVE: To determine if strawberry puree prepared under nitrogen or carbon dioxide would result in greater retention of color and anthocyanins than samples prepared under air. METHODS: Purees prepared under carbon dioxide, nitrogen or air were pasteurized and stored at 25◦C. Samples were evaluated one day, and at two week interval for eight weeks after processing for color (L*, chroma and hue), anthocyanin content and percent polymeric color. RESULTS: Purees prepared under carbon dioxide or nitrogen retained more anthocyanins (75% and 82%, respectively) following pasteurization than samples prepared under air (60% and 72%), respectively. The protective effect of oxygen exclusion on anthocyanin stability persisted throughout eight weeks of storage at 25◦C with purees prepared under carbon dioxide or nitrogen each showing 23% retention, while purees prepared under air showed only 7% and 10% retention. Purees prepared under carbon dioxide or nitrogen also had greater color stability evident by lower L*, hue and percent polymeric color and greater chroma values than puree processed under air over storage. CONCLUSIONS: Strict oxygen exclusion during strawberry processing appears to be a viable technology to improve anthocyanin and color stability, but additional technologies are needed to prevent anthocyanin losses that occur under anaerobic conditions during storage.

Improved stability of blueberry juice anthocyanins by acidification and refrigeration

BACKGROUND: Blueberry anthocyanins are susceptible to degradation during juice processing and storage of juice at ambient temperature. Methods are needed to stabilize the health-promoting anthocyanins in blueberry and other anthocyaninrich berry juices. OBJECTIVE: In this study we determined the effect of acidification (pH 2.1, 2.5 and 2.9) of blueberry juice on changes in anthocyanins and percent polymeric color in response to juice processing and during eight months of storage at ambient and refrigerated temperatures. METHODS: Three subsamples of non-pasteurized blueberry juice were adjusted to three pH levels: 2.9 (control, no pH adjustment), 2.5, and 2.1. After pH adjustment, juices were pasteurized and placed in storage at 4 and 25◦C. Samples were analyzed before (non-pasteurized) and after pasteurization, and after 2, 4, 6, and 8 months of storage at each temperature (4 and 25◦C) for anthocyanin composition by HPLC and percent polymeric color. RESULTS: Blueberry juice acidified to pH 2.1 retained higher levels of total anthocyanins and had lower percent polymeric color values than juice acidified to pH 2.5 and control juice (pH 2.9) following pasteurization. Anthocyanin arabinosides were more susceptible to thermal degradation than glucosides, galactosides and acetylated derivatives. Levels of total anthocyanins declined markedly over 8 months of storage, but juices stored at 4◦C had on average 56% higher levels of total anthocyanins than juices stored at 25◦C. Juice acidified to pH 2.1 had on average 12% and 26% higher levels of total anthocyanins than pH 2.5 and control juices, respectively. After 8 months of storage, juice acidified to pH 2.1 had 11 and 22% higher levels of total anthocyanins than pH 2.5 and control juices stored at 4◦C, and 26% and 59% higher levels of total anthocyanins than pH 2.5 and control juices stored at 25◦C. Acetylated derivatives were more prone to losses during storage than glycosides, especially in acidified juices. CONCLUSIONS: Acidification of blueberry juice coupled with refrigerated storage are effective treatments to retain healthpromoting anthocyanins.

Changes in polyphenolics during maturation of Java plum (Syzygium cumini Lam.)

Java plum (Syzygium cumini Lam.) is a rich source of polyphenolics with many purported health benefits, but the effect of maturation on polyphenolic content is unknown. Freeze-dried samples of Java plum from seven different maturity stages were analyzed for anthocyanin, flavonol, flavanonol and hydrolysable tannin composition by HPLC. Anthocyanins were first detected at the green-pink stage of maturity and increased throughout maturation with the largest increase occurring from the dark purple to black stages of maturation. Levels of gallotannins, ellagitannins, flavonols, gallic acid and ellagic acid were highest at early stages of maturation and decreased as the fruit ripened. For production of antioxidant-rich nutraceutical ingredients, fruit should be harvested immature to obtain extracts rich in hydrolysable tannins and flavonols. The exceptional anthocyanin content of black fruit may prove useful as a source of a natural colorant.

Ascorbic acid-catalyzed degradation of cyanidin-3- O-β-glucoside: Proposed mechanism and identification of a novel hydroxylated product

BACKGROUND: Many brightly colored fruits and vegetables owe their pigmentation and beneficial health effects to anthocyanins. Unfortunately, anthocyanins in the presence of ascorbic acid are readily degraded over juice processing and storage, which adversely affects color stability and potential health benefits. OBJECTIVE: This project focused on the effect of ascorbic acid as a catalyst in anthocyanin degradation. METHODS: The project involved searching for novel pigmented compounds in a simple model system composed of the most common anthocyanin cyanidin-3-O-glucoside and ascorbic acid, and a second model system consisting of blackberry extract supplemented with ascorbic acid. Degradation products were identified by HPLC-PDA and HPLC-MS. ESR was used to monitor hydroxyl radical formation in the model systems. RESULTS: Over 72 hours at ambient temperature, 67% of cyanidin-3-O-glucoside was lost in the model system during which time an unknown pigmented compound was formed. The unknown compound was also formed in a more complex model system consisting of blackberry extract and ascorbic acid. HPLC with PDA monitoring at 510 nm was used to detect a novel compound and HPLC-ESI-MS3 allowed a proposed structure to be built based on the fragmentation patterns. The unknown structure formed via oxidation of cyanidin 3-O-glucoside by ascorbic acid was identified as 6-hydroxy-cyanidin3-O-glucoside. The mechanism was substantiated with malvidin-3-O-glucoside and ascorbic acid, which produced a hydroxylated malvidin-3-Oglucoside. Production of hydroxyl radical in the base and blackberry model systems was confirmed by ESR. CONCLUSIONS:We propose that the pigmented compound is formed from hydroxyl radicals via the Haber-Weiss reaction. The addition of food grade hydroxyl radical scavengers to juices may be a viable treatment to prevent ascorbic acid-catalyzed degradation of anthocyanins.