Occurrence of ochratoxin A in cocoa by-products and determination of its reduction during chocolate manufacture

This work reports an investigation carried out to assess the natural occurrence of ochratoxin A in 168 samples from different fractions obtained during the technological processing of cocoa (shell, nibs, liquor, butter, cake and cocoa powder) and the reduction of ochratoxin A during chocolate manufacture. Ochratoxin A analyses were performed with immunoaffinity columns and detection by high performance liquid chromatography. Concerning the natural ochratoxin A contamination in cocoa by-products, the highest levels of ochratoxin A were found in the shell, cocoa powder and cocoa cake. The cocoa butter was the least contaminated, showing that ochratoxin A seems to remain in the defatted cocoa solids. Under the technological conditions applied during the manufacture of chocolate in this study and the level of contamination present in the cocoa beans, this experiment demonstrated that 93.6% of ochratoxin A present in the beans was reduced during the chocolate producing.     

A sensitive and selective method for the quantitative determination of fatty acid tryptamides as shell indicators in cocoa products

 Tetracosanoyl-2-(3-indolyl)ethane amide (lignocerinic acid tryptamide; LAT) and docosanoyl-2-(3-indolyl)ethane amide (behenic acid tryptamide; BAT) were identified as the most prominent tryptamides in cocoa shells based on electrospray ionisation mass spectrometry and ¹H NMR measurements. The structure of LAT, which is reported for the first time in cocoa shells, and also that of BAT were confirmed by synthesis. By using synthesised heptadecanoyl-2-(3-indolyl)ethane amide as the internal standard, a sensitive and reproducible method was developed for the quantification of LAT and BAT in the picogram range by means of HPLC/fluorescence detection. The detection limit was determined to be 30 pg/run. In authentic shell samples, 50-fold higher concentrations of both tryptamides were determined compared to the cocoa cotyledons. In 15 commercial chocolate samples, concentrations of 23.1–63.0 μg of the tryptamides (sum of both) per gram of fat were found. A first experiment attempted to correlate the tryptamide content with the amounts of shells in a model chocolate showed that the method is a promising tool to determine the shell content in the quality assessment of cocoa products. Received: 8 May 1998     

Mycobiota of cocoa: from farm to chocolate

The present work was carried out to study the mycobiota of cocoa beans from farm to chocolate. Four hundred and ninety-four samples were analyzed at various stages of cocoa processing: (i) primary stage at the farm (fermentation, drying, and storage), (ii) secondary stage at processing (testa, nibs, liquor, butter, cake and powder) and (iii) the final chocolate product (dark, milk, white and powdered) collected from retail outlets. Direct plating or dilution plating on Dichloran 18% Glycerol agar were used for cocoa beans and processed product analyses, respectively. Fungi were isolated and identified using different keys of identification. The largest numbers and diversity of fungi were observed in the samples collected at the farm, especially during drying and storage. The species with the highest occurrence among samples were: Absidia corymbifera, Aspergillus sp. nov., A. flavus, Penicillium paneum and yeasts. A total of 1132 potentially toxigenic fungi were isolated from the following species or species groups: A. flavus, Aspergillus parasiticus, Aspergillus nomius, Aspergillus niger group, Aspergillus carbonarius and Aspergillus ochraceus group. The highest percentage of toxigenic fungi was found at the drying and storage stages. The industrial processing reduced the fungal contamination in all fractions and no fungi were found in the final chocolate products. The knowledge of which fungi are dominant at each processing stage of cocoa provides important data about their ecology. This understanding leads to a reduction in fungal spoilage and mycotoxin production in this product.     

Evaluation of the effect of processing on cocoa polyphenols: antiradical activity,anthocyanins and procyanidins profiling from raw beans to chocolate

The content and composition of anthocyanins and procyanidins in fermented cocoa beans (from different geographic origins: Ecuador, Cameroon, Ivory Coast, Ghana and Nigeria), roasted nibs, cocoa mass and chocolate were determined, beside the determination of the total antiradical capacity. Concerning geographic origin, cocoa beans and processed products from Ecuador showed the highest levels of anthocyanins, followed by Nigeria and Cameroon. Generally, as cocoa beans were further processed, the levels of anthocyanins and flavan‐3‐ols decreased. The largest observed losses of phenolics occurred during roasting. A progressive decreasing trend in polyphenol concentration was observed in the other processed samples as well. Despite the original content of polyphenols in raw cocoa beans, technological processes imply a significant impact on cocoa quality, confirming the need of specific optimisation to obtain high value chocolate.     

Zur Eisenkontamination in Kakao und Kakaoerzeugnissen

Zusammenfassung Die hier beschriebene Untersuchung bezieht sich auf die Eisenkontamination in Kakao und Kakaoerzeugnissen. Es wurden sowohl Halbfabrikate als auch Endprodukte untersucht, wobei man in Kakaobohnen durchschnittlich 29 mg/kg Gesamteisen (ionisch und metallisch) fand. In Kakaoschalen lag der Eisengehalt ungefähr 10mal höher. Es stellte sich heraus, daß beim Mahlen des gerösteten Kernbruchs zu Kakaomasse der Eisengehalt deutlich zunimmt: Durchschnittlich fand man 150 mg Eisen pro kg Masse. Die Untersuchungen bewiesen, daß der Eisengehalt während der Bearbeitung ca. 75 bis selbst 200% zunahm. Kakaopulver enthält durchschnittlich mehr Eisen (238 mg/kg) als die Masse, was mit der Erniedrigung des Fettgehaltes durch Pressen und Mahlen des Kakaopreßkuchens zusammenhängt. Die Eisenmengen der aus verschiedenen Ländern aus dem Handel bezogenen Kakaopulver- und Schokoladeproben wiesen keine nennenswerten Unterschiede auf.

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On the iron contamination in cocoa and chocolate products

Summary The investigation in question deals with the iron contamination in cocoa and chocolate products. Semi finished goods as well as finished products were examined. An average of 29 mg/kg total iron (i.e. ionic + metallic iron) was found in cocoabeans. The iron content of cocoa shells was approximately 10 fold higher. The process of grinding roasted nibs to cocoa-mass (liquor) resulted in a noticeable increase of the quantity of iron to an average amount of 150 mg/kg mass. This process thus produced an increase of the iron content of approximately 75 to as much as 200%. The cocoa powders contained more iron (238 mg/kg) than the cocoa mass, which is linked to a reduction of the fat content by pressing and by grinding of the presscake. The quantities of iron observed in commercial samples of cocoa powder from different countries did not show appreciable differences.

     

Bioactive and Sensory Properties of Herbal Spirit Enriched with Cocoa (Theobroma cacao L.) Polyphenolics

In the Southeast European and Mediterranean regions, consumption of various alcoholic beverages in the form of plain and aromatized spirits and liqueurs is an important part of traditional local gastronomy. Especially herbal spirits and liquors are widely spread and consumed. The objective of this study was to evaluate the potential of using cocoa raw materials (cocoa beans, cocoa nibs or cocoa liquor) in order to enhance the bioactive profile of traditional herbal liqueur, and to produce an appealing cocoa-flavoured alcoholic beverage. Therefore, the polyphenolic profile, antioxidative and sensory properties of herbal liquors containing the macerated cocoa raw materials were monitored during 6 months, in order to evaluate the kinetics of cocoa polyphenols release and optimise the maceration procedure for obtaining the best cocoa-enriched herbal spirit. Compared to plain herbal liquor without the additions, the obtained herbal liqueurs exhibited significantly higher content of polyphenolic antioxidants. Among the used cocoa raw materials for the maceration, cocoa nibs were evaluated as the best source of polyphenolic compounds (herbal liqueur containing cocoa nibs, 3,081.82 mg GAE/L), followed by cocoa liquor (1,897.73 mg GAE/L) and cocoa beans (1,358.64 mg GAE/L). Prolonged maceration time (up to 6 months) resulted with an increase in the content of polyphenolic compounds and the antioxidant capacity of herbal liqueurs. Herbal liqueurs containing the cocoa raw materials of bigger particle size (cocoa beans and cocoa nibs) exhibited better sensory properties (overall acceptability and chocolate-like flavour) than herbal liqueur containing cocoa liquor.     

Modelling and experimental evaluation of high-pressure expression of cocoa nibs

The ability of the Shirato model to describe the expression of dry cocoa nibs in a hydraulic press at pressures of 20–80 MPa was compared with that of a numerically solved conservation laws model based on mass and momentum balances. Experimental data were used to determine the material constants involved in both models at 40, 80 and 100 °C. The Shirato model more accurately describes the final average porosity at different pressures. The Shirato model was therefore used to calculate the influence of the pressure, pressing time and mass of nibs used on the expression process. The calculation results followed the experimentally observed trends. The Shirato model was also used to describe the expression behaviour of cocoa liquor (finely grinded cocoa nibs) at 100 °C and pressures of 20–70 MPa. It was calculated that the filtration stage is absent at these pressures. However, the behaviour of cocoa liquor can only be accurately described with the Shirato model for the last part of the expression process (>100 s).     

Soluble Albumin and Biological Value of Protein in Cocoa (Theobroma cacao L.) Beans as a Function of Roasting Time

ABSTRACT: An association has been identified between the extent of roasting and the amount of extractable protein from the cocoa bean, its nutritive value, and the sensorial quality of the liquor. Cocoa nibs from fermented seeds ( Theobroma cacao L.) were precision-roasted at 150°C for 0, 30, 34, 38, 42, and 46 min and the protein fraction extracted. From the beginning of roasting, until minute 38, about 87% of the proteins were extractable, but the extractability substantially decreased to 72.7% at 42 min and to 65.3% at 46 min. Both total soluble protein determination and albumin concentration of the roasted nibs diminished slightly until minute 38, when acceptable sensory characteristics were obtained for the liquor. Both total nitrogen and capillary-electrophoretic separation and quantification of the albumin showed that the amounts of extractable protein in this fraction consistently followed a cyclic pattern until minute 42, irreversibly decreasing thereafter. Biological evaluation of the protein from the cocoa nibs roasted for the various times showed that at the point that the sensory rating approached that of a commercial liquor, the albumin content and nutritive value were still high. The findings suggest that with moderate, uniform roasting it may not be necessary to sacrifice the protein's biological value for the sensorial attributes of chocolate in a standard commercial roast.     

A comparison of antioxidant properties between artisan‐made and factory‐produced chocolate

The antioxidant capacities and the total phenolic content in cocoa liquor directly manufactured chocolate from an artisan manufacturer were measured using different in vitro methods (BR, TEAC, and Folin–Ciocalteu Reagent). These parameters were then compared with those of a chocolate made by a leading manufacturing company producing chocolate and cocoa‐containing products. A statistical analysis of the collected data showed that the antioxidant properties of the artisan‐made chocolate are significantly better than those of the factory‐produced one. These results were ascribed to the fact that all the bioactive components in the cocoa beans are better preserved in the artisan‐made chocolate.     

On-farm implementation of a starter culture for improved cocoa bean fermentation and its influence on the flavour of chocolates produced thereof

Cocoa bean fermentations controlled by means of starter cultures were introduced on several farms in two different cocoa-producing regions (West Africa and Southeast Asia). Two starter culture mixtures were tested, namely one composed of Saccharomyces cerevisiae H5S5K23, Lactobacillus fermentum 222, and Acetobacter pasteurianus 386B (three heaps and one box), and another composed of L. fermentum 222 and A. pasteurianus 386B (seven heaps and one box). In all starter culture-added cocoa bean fermentation processes, the inoculated starter culture species were able to outgrow the natural contamination of the cocoa pulp-bean mass and they prevailed during cocoa bean fermentation. The application of both added starter cultures resulted in fermented dry cocoa beans that gave concomitant milk and dark chocolates with a reliable flavour, independent of cocoa-producing region or fermentation method. The addition of the lactic acid bacterium (LAB)/acetic acid bacterium (AAB) starter culture to the fermenting cocoa pulp-bean mass accelerated the cocoa bean fermentation process regarding citric acid conversion and lactic acid production through carbohydrate fermentation. For the production of a standard bulk chocolate, the addition of a yeast/LAB/AAB starter culture was necessary. This enabled an enhanced and consistent ethanol production by yeasts for a successful starter culture-added cocoa bean fermentation process. This study showed possibilities for the use of starter cultures in cocoa bean fermentation processing to achieve a reliably improved fermentation of cocoa pulp-bean mass that can consistently produce high-quality fermented dry cocoa beans and flavourful chocolates produced thereof.     

The Content of Polyphenolic Compounds in Cocoa Beans (Theobroma cacao L.), Depending on Variety,Growing Region,and Processing Operations: A Review

Polyphenols form the largest group of compounds among natural antioxidants, which largely affect the overall antioxidant and antifree radical activity of cocoa beans. The qualitative and quantitative composition of individual fractions of polyphenolic compounds, even within one species, is very diverse and depends on many factors, mainly on the area of cocoa trees cultivation, bean maturity, climatic conditions during growth, and the harvest season and storage time after harvest. Thermal processing of cocoa beans and cocoa derivative products at relatively high temperatures may in addition to favorable physicochemical, microbiological, and organoleptic changes result in a decrease of polyphenols concentration. Technological processing of cocoa beans negatively affects the content of polyphenolic compounds.     

Thermal,structural and rheological characteristics of dark chocolate with different compositions

The effect of different cocoa composition of dark chocolate samples and their ingredients on their thermal, structural and rheological characteristics was investigated. Thermal behavior was evaluated by means of differential scanning calorimetry (DSC), while the crystal morphology was observed by polarized light optical microscopy. The rheological measurements were carried out using both continuous and oscillatory experiments. The formation of more stable polymorphic structures was time and temperature dependent; and it was not affected by either cocoa composition or particle sizes. The kinetics of crystallization was determined by a step crystallization method and modeled by the Avrami equation, it was accelerated by solid particles concentration, lower particle size and lower crystallization temperatures. Negative spherulites with featherlike microstructures defined the time dependent crystal growth and were consistent with Avrami indexes of 3–4. Under continuous shear, cocoa butter was well described by the Bingham rheological model, while Casson and Carreau equations modeled the flow of cocoa liquor and chocolate samples. However the Carreau model was preferred for presenting better fittings and for predicting apparent viscosities at low and at high shear rates. From both, continuous and oscillatory experiments, it was found that composition of chocolate samples in terms of fat and nonfat cocoa solids, and sugar content, affected their rheological behavior. The solid liquid transition of chocolate samples and cocoa liquor was obtained at a yield stress of around 1 Pa from both continuous and oscillatory shear experiments.     

Fluidized bed roasting of cocoa nibs speeds up processing and favors the formation of pyrazines

Roasting is an important step in cocoa processing causing water loss and generating volatile compounds responsible for chocolate aroma like nitrogen-heterocycles. In this study, the comparison of two techniques, oven roasting, and fluidized bed roasting, in terms of effective water diffusivity (De) and activation energies of formation (Ea) of nitrogen-heterocycles was achieved with cocoa nibs. Fluidized bed roasting, recognized for its energy efficiency and low-footprint synthesis, was 16 times faster than oven roasting. The order of magnitude of De in fluidized-bed-roasted nibs was −8, while it was −9 in the oven-roasted nibs. Moreover, the a_w was 50% higher in fluidized-bed-roasted nibs than in the oven-roasted ones. The Ea of nitrogen-heterocycles ranged roughly between 40 and 80 kJ/mol. Those values were lower under fluidized bed roasting than under oven roasting. The more effortless water mobility within fluidized-bed-roasted cocoa demanded lower Ea, and favored the formation of nitrogen-heterocyclics.Industrial relevanceThis study can inspire cocoa manufacturers and equipment designers to pursue the formation of nitrogen-heterocycles during the roasting process of cocoa. It can be done either by adapting and scaling the current fluidized bed coffee roasters to cocoa beans or nibs; or by exploring other alternatives capable of leading enough water diffusivity and water activity in the cocoa nibs, as reported here. These physicochemical conditions undoubtedly boosted the formation of volatile compounds responsible for chocolate aroma, e.g., the pyrazines, without carrying the formation of typical-burn volatile compounds. This natural way of favoring the generation of pyrazines in cocoa nibs could contribute to clean labels by reducing or avoiding the subsequent use of flavorings. The implementation of efficient heat-transfer techniques during roasting, e.g., fluidized bed roasting, could reduce the processing cost and improve sustainability. Studies in the matter of sensory profile, and energy consumption/conversion are called for future research.     

ITS-RFLP characterization of black <Emphasis Type="Italic">Aspergillus</Emphasis> isolates responsible for ochratoxin A contamination in cocoa beans

In the present study, ochratoxigenic mycobiota in cocoa beans was identified at species level by digestion of the ITS products using the endonucleases HhaI, NlaIII and RsaI. Of the 132 isolates of Aspergillus section Nigri collected from cocoa beans, 89 were identified as A. tubingensis, 27 as A. niger, 10 as A. tubingensis-like and 6 as A. carbonarius. No variation was observed between RFLP patterns (C, N, T1 and T2) described previously for grape isolates and those of the cocoa isolates analysed. With respect to OTA-producing fungi, a high percentage of black aspergilli (50.7%) was able to produce OTA. Additionally, most of the OTA-producing isolates were of moderate toxigenicity, producing amounts of OTA from 10 μg g⁻¹ to 100 μg g⁻¹. Percentages of OTA-producing isolates in the A. niger aggregate were higher than in other substrates, ranging from 30% to 51.7%. Furthermore, the detected levels of OTA production in the A. niger aggregate, particularly in A. tubingensis species was higher than in A. carbonarius, ranging from 0.7 μg g⁻¹ to 120 μg g⁻¹ (mean 24.55 μg g⁻¹). Due to the high occurrence, percentage of ocratoxigenic isolates and their ability to produce OTA, isolates belonging to the A. niger aggregate could be considered as the main cause of OTA contamination in cocoa beans used for manufacturing cocoa products.     

Fatty acid tryptamides as shell indicators for cocoa products and as quality parameters for cocoa butter

The methods used to date to determine the shell content in cocoa products are very time-consuming, protracted and not specific enough, meaning that with the development of a new high-performance liquid chromatography (HPLC) method using fluorescence detection, a considerably more specific process is now available. Fatty acid tryptamides can be drawn on as indicator substances for detecting the shell content in cocoa products. The relevant substance species are docosanoyl-2-(3-indolyl)ethylamide (behenic acid tryptamide, BAT) and tetracosanoyl-2-(3-indolyl)ethylamide (lignoceric acid tryptamide, LAT). To allow conclusions on the average levels of fatty acid tryptamides (FAT) in cocoa products to be drawn, 433 cocoa samples were analysed. The natural tryptamide concentrations in cocoa shells and cocoa nibs or cocoa liquors varied significantly. The average ratio of cocoa shells to cocoa nibs/cocoa liquors is 16:1. As a result of these differences in concentration, the shell content can be determined with a high degree of accuracy via the fatty acid tryptamides in cocoa. This method also allows conclusions to be drawn on the quality of cocoa butter. The tryptamide concentrations in pressed cocoa butter and in expeller butter respectively vary greatly, so that it is possible through the FAT levels determined to gain an insight into the method of production of cocoa butter.     

Temperature influences epimerization and composition of flavanol monomers,dimers and trimers during cocoa bean roasting

Cocoa consumption is suggested to promote many health benefits, since cocoa is a rich source of flavanols; but amounts and profiles of flavanols depend strongly on the bean type, origin and manufacturing process. Roasting is known as a crucial step in technical treatment of cocoa, which leads to flavanol losses and modifications, especially the epimerization of (−)-epicatechin to (−)-catechin. This study monitors the influence of cocoa bean roasting on the composition of flavanol monomers to trimers, with special focus on epimerization, which was quantified for procyanidin dimers, and also observed for trimers for the first time. Five dimeric and two trimeric potential epimerization products were detected and the extent of epimerization during cocoa roasting was shown to be a function of temperature. The data also showed remarkable variations in the change of flavanol content. The quantified flavanols decreased about 50% in Java beans and increased about 30% in Ivory Coast beans, despite being roasted under equal conditions.     

Fermentation of cocoa beans: influence of microbial activities and polyphenol concentrations on the flavour of chocolate

BACKGROUND: Spontaneous cocoa bean fermentation is characterised by a succession of microbial activities. Cocoa flavour precursors are developed during fermentation and drying of cocoa beans. Polyphenols and alkaloids contribute to astringency and bitterness of cocoa and chocolate. RESULTS: Population dynamics, metabolite target analyses, and chocolate production were performed for seven independent spontaneous cocoa bean heap fermentations in Ghana. Although the same micro‐organisms were involved in these heaps, carried out at different farms or in different seasons, heap temperatures and microbial metabolite concentrations were different. This could be due to heterogeneity and size of the heaps, but was mainly ascribed to microbial variability. Indeed, differences in microbial activity could be linked with the flavour of chocolates made from the corresponding dried, fermented cocoa beans. Whereas the polyphenol and alkaloid contents of cocoa beans were crop‐ and heap‐dependent, epicatechin and theobromine levels decreased during fermentation due to diffusion out of the bean cotyledons and polyphenol oxidation and condensation. Residual levels were responsible for the degree of bitterness of the final chocolates. CONCLUSION: Differences in microbial activities between different heap fermentations can result in dried fermented cocoa beans and chocolates with different flavour characteristics. Hence, fermentation control may direct the flavour of chocolate. Copyright © 2008 Society of Chemical Industry     

Effect of farm and industrial processing on the amino acid profile of cocoa beans

An investigation into the amino acid profiles of unfermented and fermented cocoa nibs, as well as process-line cocoa nibs (P-LCN) and processed cocoa cake samples (PCCS) was carried out. In the unfermented cocoa nibs, Glu (128 mg/g crude protein i.e. 128 mg/gcp) was the most abundant amino acid whilst the most concentrated essential amino acid in the same sample was Leu (72.2 mg/g crude protein); in the fermented cocoa nibs, a similar trend was observed, with respective values of Glu (153 mg/gcp) and Leu (62.4 mg/gcp). Lys (181 mg/gcp) was most abundant amino acid in P-LCN and Ile (63.3 mg/gcp) was the second most abundant; also, in PCCS, Lys (52.7 mg/gcp) was the most abundant amino acid but Asp (43.7 mg/gcp) was the second most abundant. The total amino acid content was (mg/gcp), 641 (unfermented nibs), 708 (fermented nibs), 635 (P-LCN) and 368 (PCCS), with corresponding essential amino acids of 300, 287, 478 and 185 (all with His), respectively. Based on whole hen’s egg, the limiting amino acids for the samples were: Ser (unfermented nibs), Met (fermented nibs), Ala (P-LCN) and Val (PCCS), whereas under provisional amino acid scoring pattern, they were: Met + Cys (unfermented nibs), Met + Cys (fermented nibs), Thr (P-LCN) and Val (PCCS). Prolonged and high heat treatments appeared to have reduced the essential amino acids of the PCCS as compared to the P-LCN. Significant differences existed between contents of essential amino acids and non-essential amino acids at p < 0.05 in unfermented cocoa nibs, fermented cocoa nibs and P-LCN.     

Flavor formation and character in cocoa and chocolate: a critical review

Chocolate characters not only originate in flavor precursors present in cocoa beans, but are generated during post-harvest treatments and transformed into desirable odor notes in the manufacturing processes. Complex biochemical modifications of bean constituents are further altered by thermal reactions in roasting and conching and in alkalization. However, the extent to which the inherent bean constituents from the cocoa genotype, environmental factors, post-harvest treatment, and processing technologies influence chocolate flavor formation and relationships with final flavor quality, has not been clear. With increasing speciality niche products in chocolate confectionery, greater understanding of factors contributing to the variations in flavor character would have significant commercial implications.