Determination of total procyanidins in selected chocolate and confectionery products using DMAC.

A simple, specific, high-throughput colorimetric method based on the reaction of 4-dimethylaminocinnamaldehyde (DMAC) with flavan-3-ols was developed to determine total procyanidins in selected cacao-based products. Extracts of defatted samples were dispensed into a 96-well plate and reacted with DMAC. The absorbance of the reaction products was measured at 640 nm and compared to commercially available procyanidin B2 as a standard. The use of the 96-well plates and a plate reader dramatically improved sample throughput. A standard protocol was established and used for further studies. The calibration was found to be linear from 1-100 ppm. The DMAC reagent reacted relatively specifically to (-)-epicatechin, (+)-catechin, epigallocatechin, gallocatechin, the gallates of catechin, epicatechin, gallocatechin, and epigallocatechin, oligomeric procyanidins of cocoa up to n=4, and A-type procyanidins. Little or no reaction occurred with cyanidins and representative compounds of phenolic acids, flavones, flavanones, flavonols, anthocyanidins, isoflavones, and stilbenes. Sample precision studies were carried out on 10 different test materials over several weeks, and yielded RSD values of 4.0 to 9.5%. The method was ring-tested in three laboratories using blinded test materials including cocoa beans, cocoa powder, chocolate liquor, dark chocolate, and milk chocolate. There was excellent agreement of the results between laboratories.

Characterization of primary standards for use in the HPLC analysis of the procyanidin content of cocoa and chocolate containing products.

This report describes the characterization of a series of commercially available procyanidin standards ranging from dimers DP = 2 to decamers DP = 10 for the determination of procyanidins from cocoa and chocolate. Using a combination of HPLC with fluorescence detection and MALDI-TOF mass spectrometry, the purity of each standard was determined and these data were used to determine relative response factors. These response factors were compared with other response factors obtained from published methods. Data comparing the procyanidin analysis of a commercially available US dark chocolate calculated using each of the calibration methods indicates divergent results and demonstrate that previous methods may significantly underreport the procyanidins in cocoa-containing products. These results have far reaching implications because the previous calibration methods have been used to develop data for a variety of scientific reports, including food databases and clinical studies.

Antioxidant activity and polyphenol and procyanidin contents of selected commercially available cocoa-containing and chocolate products in the United States.

In the United States, commercially available foods, including cocoa and chocolate, are being marketed with statements referring to the level of antioxidant activity and polyphenols. For cocoa-containing foods, there has been no comprehensive survey of the content of these and other chemistries. A survey of cocoa and chocolate-containing products marketed in the United States was conducted to determine antioxidant activity and polyphenol and procyanidin contents. Commercially available samples consisted of the top market share products in each of the following six categories: natural cocoa, unsweetened baking chocolate, dark chocolate, semisweet baking chips, milk chocolate, and chocolate syrup. Composite samples were characterized using four different methods: oxygen radical absorbance capacity (ORAC), vitamin C equivalence antioxidant capacity (VCEAC), total polyphenols, and procyanidins. All composite lots were further characterized for percent nonfat cocoa solids (NFCS) and percent fat. Natural cocoas had the highest levels of antioxidant activities, total polyphenols, and procyanidins followed by baking chocolates, dark chocolates and baking chips, and finally milk chocolate and syrups. The results showed a strong linear correlation between NFCS and ORAC (R (2) = 0.9849), total polyphenols (R (2) = 0.9793), and procyanidins (R (2) = 0.946), respectively. On the basis of principal component analysis, 81.4% of the sample set was associated with NFCS, antioxidant activity, total polyphenols, and procyanidins. The results indicated that, regardless of the product category, NFCS were the primary factor contributing to the level of cocoa antioxidants in the products tested. Results further suggested that differences in cocoa bean blends and processing, with the possible exception of Dutching, are minor factors in determining the level of antioxidants in commercially available cocoa-containing products in the United States.

Inhibition of key digestive enzymes by cocoa extracts and procyanidins.

This study determined the in vitro inhibitory effects of cocoa extracts and procyanidins against pancreatic α-amylase (PA), pancreatic lipase (PL), and secreted phospholipase A(2) (PLA(2)) and characterized the kinetics of such inhibition. Lavado, regular, and Dutch-processed cocoa extracts as well as cocoa procyanidins (degree of polymerization (DP) = 2-10) were examined. Cocoa extracts and procyanidins dose-dependently inhibited PA, PL, and PLA(2). Lavado cocoa extract was the most potent inhibitor (IC(50) = 8.5-47 µg/mL). An inverse correlation between log IC(50) and DP (R(2) > 0.93) was observed. Kinetic analysis suggested that regular cocoa extract, the pentamer, and decamer inhibited PL activity in a mixed mode. The pentamer and decamer noncompetitively inhibited PLA(2) activity, whereas regular cocoa extract inhibited PLA(2) competitively. This study demonstrates that cocoa polyphenols can inhibit digestive enzymes in vitro and may, in conjunction with a low-calorie diet, play a role in body weight management.

Impact of fermentation, drying, roasting and Dutch processing on flavan-3-ol stereochemistry in cacao beans and cocoa ingredients.

This paper reports a systematic study of the level of flavan-3-ol monomers during typical processing steps as cacao beans are dried, fermented and roasted and the results of Dutch-processing. Methods have been used that resolve the stereoisomers of epicatechin and catechin. In beans harvested from unripe and ripe cacao pods, we find only (-)-epicatechin and (+)-catechin with (-)-epicatechin being by far the predominant isomer. When beans are fermented there is a large loss of both (-)-epicatechin and (+)-catechin, but also the formation of (-)-catechin. We hypothesize that the heat of fermentation may, in part, be responsible for the formation of this enantiomer. When beans are progressively roasted at conditions described as low, medium and high roast conditions, there is a progressive loss of (-)-epicatechin and (+)-catechin and an increase in (-)-catechin with the higher roast levels. When natural and Dutch-processed cacao powders are analyzed, there is progressive loss of both (-)-epicatechin and (+)-catechin with lesser losses of (-)-catechin. We thus observe that in even lightly Dutch-processed powder, the level of (-)-catechin exceeds the level of (-)-epicatechin. The results indicate that much of the increase in the level of (-)-catechin observed during various processing steps may be the result of heat-related epimerization from (-)-epicatechin. These results are discussed with reference to the reported preferred order of absorption of (-)-epicatechin > (+)-catechin > (-)-catechin. These results are also discussed with respect to the balance that must be struck between the beneficial impact of fermentation and roasting on chocolate flavor and the healthful benefits of chocolate and cocoa powder that result in part from the flavan-3-ol monomers.

Impact of fermentation, drying, roasting, and Dutch processing on epicatechin and catechin content of cacao beans and cocoa ingredients.

Low molecular weight flavan-3-ols are thought to be responsible, in part, for the cardiovascular benefits associated with cocoa powder and dark chocolate. The levels of epicatechin and catechin were determined in raw and conventionally fermented cacao beans and during conventional processing, which included drying, roasting, and Dutch (alkali) processing. Unripe cacao beans had 29% higher levels of epicatechin and the same level of catechin compared to fully ripe beans. Drying had minimal effect on the epicatechin and catechin levels. Substantial decreases (>80%) in catechin and epicatechin levels were observed in fermented versus unfermented beans. When both Ivory Coast and Papua New Guinea beans were subjected to roasting under controlled conditions, there was a distinct loss of epicatechin when bean temperatures exceeded 70 °C. When cacao beans were roasted to 120 °C, the catechin level in beans increased by 696% in unfermented beans, by 650% in Ivory Coast beans, and by 640% in Papua New Guinea fermented beans compared to the same unroasted beans. These results suggest that roasting in excess of 70 °C generates significant amounts of (-)-catechin, probably due to epimerization of (-)-epicatechin. Compared to natural cocoa powders, Dutch processing caused a loss in both epicatechin (up to 98%) and catechin (up to 80%). The epicatechin/catechin ratio is proposed as a useful and sensitive indicator for the processing history of cacao beans.

Stability of cocoa antioxidants and flavan-3-ols over time.

Several recent reports have been published indicating that the antioxidant activity of olive oil and tea leaves is not stable over product shelf lives of about one year. We have measured the antioxidant activity, total polyphenols, flavan-3-ols monomers, and procyanidin levels in milk and dark chocolate, in cocoa powder, and in cocoa beans. Results show that for the cocoa products studied, antioxidant activity, and flavan-3-ol levels are stable over typical shelf lives of one year under controlled storage and over 2 years in ambient storage in the laboratory. We also show that 80 year old cocoa powder and 116 year old cocoa beans still show very high levels of antioxidant activity and flavan-3-ol content.

Survey of commercially available chocolate- and cocoa-containing products in the United States. 2. Comparison of flavan-3-ol content with nonfat cocoa solids, total polyphenols, and percent cacao.

A survey of a broad range of chocolate- and cocoa-containing products marketed in the United States was conducted to provide a more detailed analysis of flavan-3-ol monomers, oligomers, and polymers, which can be grouped into a class of compounds called procyanidins. Samples consisted of the three or four top-selling products within the following six categories: natural cocoa powder, unsweetened baking chocolate, dark chocolate, semisweet baking chips, milk chocolate, and chocolate syrup. Composite samples were characterized for percent fat (% fat), percent nonfat cocoa solids (% NFCS), antioxidant level by ORAC, total polyphenols, epicatechin, catechin, total monomers, and flavan-3-ol oligomers and polymers (procyanidins). On a gram weight basis epicatechin and catechin content of the products follow in decreasing order: cocoa powder > baking chocolate > dark chocolate = baking chips > milk chocolate > chocolate syrup. Analysis of the monomer and oligomer profiles within product categories shows there are two types of profiles: (1) products that have high monomers with decreasing levels of oligomers and (2) products in which the level of dimers is equal to or greater than the monomers. Results show a strong correlation (R(2) = 0.834) of epicatechin to the level of % NFCS and also very good correlations for N = 2-5 oligomers to % NFCS. A weaker correlation was observed for catechin to % NFCS (R(2) = 0.680). Other analyses show a similar high degree of correlation with epicatechin and N = 2-5 oligomers to total polyphenols, with catechin being less well correlated to total polyphenols. A lesser but still good correlation exists between the calculated percent cacao (calcd % cacao) content, a proxy for percent cacao, and these same flavanol measures, with catechin again showing a lesser degree of correlation to calcd % cacao. Principal component analysis (PCA) shows that the products group discretely into five classes: (1) cocoa powder, (2) baking chocolate, (3) dark chocolate and semisweet chips, (4) milk chocolates, and (5) syrup. PCA also shows that most factors group closely together including the antioxidant activity, total polyphenols, and the flavan-3-ol measures with the exception of catechin and % fat in the product, which group separately. Because catechin distribution appears to be different from the other flavan-3-ol measures, an analysis of the epicatechin to catechin ratio was done, indicating there is a >5-fold variation in this measure across the products studied. The cocoa-containing products tested range from cocoa powder with 227.34 +/- 17.23 mg of procyanidins per serving to 25.75 +/- 9.91 mg of procyanidins per serving for chocolate syrup. These results are discussed with respect to other studies on commercial products, the bioavailability of the flavanols, and the possible role of processing on the amount of catechin in products.

Survey of the trans-resveratrol and trans-piceid content of cocoa-containing and chocolate products.

Dietary resveratrol (3,4',5-trihydroxystilbene) has been implicated in the health benefits associated with grapes and red wine, more specifically with potential benefits for metabolic syndrome, energy use, and increased endurance. Levels of trans-resveratrol and its glucoside, trans-piceid, were determined in 19 top selling commercially available cocoa-containing and chocolate products from the U.S. market. Amounts of trans-resveratrol and trans-piceid were closely correlated with the amount of nonfat cocoa solids (NFCS) in the cocoa-containing products. Among these products, trans-resveratrol levels were highest in cocoa powders (1.85 +/- 0.43 microg/g), followed by unsweetened baking chocolates (1.24 +/- 0.22), semisweet chocolate baking chips (0.52 +/- 0.14), dark chocolates (0.35 +/- 0.08), milk chocolates (0.10 +/- 0.05), and chocolate syrups (0.09 +/- 0.02). These cocoa-containing and chocolate products have about 3-5 times more trans-piceid than trans-resveratrol. Levels of trans-piceid were highest in the cocoa powders (7.14 +/- 0.80 microg/g), followed by unsweetened baking chocolates (4.04 +/- 0.14), semisweet chocolate baking chips (2.01 +/- 0.18), dark chocolates (1.82 +/- 0.36), milk chocolates (0.44 +/- 0.06), and chocolate syrups (0.35 +/- 0.06). On an equal weight basis, cocoa powder had about half as much trans-resveratrol as the average California red wine. On a per serving basis, cocoa-containing and chocolate products had less trans-resveratrol than red wine and grape juice but more than roasted peanuts. Overall, these cocoa-containing and chocolate products rank second after red wines and grape juice in foods with the highest levels of total trans-resveratrol in the diet.

Impact of alkalization on the antioxidant and flavanol content of commercial cocoa powders.

Cocoa is a food ingredient that is important for the contribution of flavor to foods but is also associated with potential health benefits. The chemistry thought to be responsible for its cardiovascular health benefits is the flavanol (flavan-3-ol) antioxidants. Evidence from the literature indicates that natural cocoas are high in flavanols, but when the cocoa is processed with alkali, also known as Dutch processing or Dutching, the flavanols are substantially reduced. This paper provides a survey of the physical and chemical composition of representative natural cocoas and lightly, medium, and heavily alkalized cocoas. As part of the survey, both brown/black and red/brown alkali-processed cocoas were measured. Natural cocoa powders have an extractable pH of 5.3-5.8. Alkalized cocoa powders were grouped into lightly treated (pH 6.50-7.20), medium-treated (pH 7.21-7.60), and heavily treated (pH 7.61 and higher). The natural, nonalkalized powders had the highest ORAC and total polyphenols and flavanols (including procyanidins). These chemical measurements showed a linear decrease as the extractable pH of the cocoa powder increased. Likewise, the flavanol monomers, oligomers, and polymers all showed a linear decrease with increasing pH of the final cocoa powder. When brown/black cocoa powders were compared to red cocoa powders, similar decreases in flavanols were observed with increased alkalization. The average total flavanol contents were 34.6 +/- 6.8 mg/g for the natural cocoas, 13.8 +/- 7.3 mg/g for the lightly processed cocoas, 7.8 +/- 4.0 mg/g for the medium processed cocoas, and 3.9 +/- 1.8 mg/g for the heavily processed cocoa powders. The observed linear and predictable impact of alkalization on flavanol content is discussed with respect to other reports in the literature as well as what implications it may have on diet and food manufacturing.