State‐of‐the‐Art Chocolate Manufacture: A Review

The aroma, taste, shine, snap, smoothness, “melt‐in‐your‐mouth” sensation, and texture are all qualities that define chocolate, and all depend on how the cocoa and the chocolate itself are processed. Postharvest handling of the cocoa (fermentation, drying, cleaning, storage, and transport) and its transformation into chocolate (roasting, grinding, conching, tempering, molding, and the addition of core and other ingredients), as well as the packaging, storage, transport, and refrigeration of the finished product all have an important influence on the characteristics of chocolate. The aim of this review was to identify and study the key factors, including microbiological aspects that affect the quality of chocolate, from harvesting the beans right up to the manufacture of the finished products.     

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     

Cadmium and lead in cocoa powder and chocolate products in the US Market

Cocoa powder and chocolate products are known to sometimes contain cadmium (Cd) and lead (Pb) from environmental origins. A convenience sample of cocoa powder, dark chocolate, milk chocolate, and cocoa nib products was purchased at retail in the US and analysed using inductively coupled plasma mass spectrometry to assess Cd and Pb concentrations. Cd and Pb were evaluated in relation to the percent cocoa solids and to the reported origin of the cocoa powder and chocolate products. Cd ranged from 0.004 to 3.15 mg/kg and Pb ranged from <LOD to 0.38 mg/kg. Cd and Pb were significantly correlated with percent cocoa, with correlations varying by product type and geographic origin. Geographic variation was observed for Cd, with higher Cd concentrations found in products reported as originating from Latin America than from Africa. The influence of percent cocoa solids and cocoa origin on Cd levels are relevant to international standards for Cd in chocolate products.     

Flavor Chemistry of Cocoa and Cocoa Products—An Overview

Cocoa originates from beans of the cocoa tree (Theobroma cacao L.) and it is an important commodity in the world and the main ingredient in chocolate manufacture. Its value and quality are related to unique and complex flavors. Bulk cocoas (Forastero type) exhibit strong basic cocoa notes, whereas fine varieties (Criollo, Nacional) show aromatic, floral, or smoother flavor characteristics. About 600 various compounds (alcohols, carboxylic acids, aldehydes, ketones, esters, and pyrazines) have been identified as odor‐active components. The specific cocoa aroma arises from complex biochemical and chemical reactions during the postharvest processing of raw beans, and from many influences of the cocoa genotype, chemical make‐up of raw seeds, environmental conditions, farming practices, processing, and manufacturing stages. There has been much research on cocoa flavor components. However, the relationships between all chemical components that are likely to play a role in cocoa flavor, their sensory properties, and the sources and mechanisms of flavor formation are not fully understood. This paper provides an overview on cocoa flavor from a compositional and a sensory perspective. The nonvolatile and volatile chemical components of cocoa and chocolate flavor, and their sensory properties correlated to the main influences involved in flavor formation, are reviewed.     

Performance of different drying methods and their effects on the chemical quality attributes of raw cocoa material

Studies were carried out to investigate the impact of different drying processes on the chemical quality traits of raw cocoa beans. The pH of less fermented cocoa is higher than the well‐fermented cocoa’s. The sun‐dried beans pH ranged from 4.5 to 5.5, while the pH of both oven‐ and mixed‐dried beans was between 3.8 and 5.2. The sun‐dried beans contained lower volatile acidity than oven‐dried beans. Artificially dried beans resulted in higher free acidity content when compared to both sun‐ and mixed‐dried beans. Ammonium nitrogen content in raw cocoa beans is not influenced by the drying methods. Free fatty acid content increases slowly but remains below the critical value of 1.75% whatever the drying processes. While oven‐dried beans show the FFA content above 0.70% both of sun‐ and mixed‐dried beans are associated with FFA content below 0.70%.     

Determining degree of roasting in cocoa beans by artificial neural network (ANN)‐based electronic nose system and gas chromatography/mass spectrometry (GC/MS)

BACKGROUND

Roasting is a critical step in chocolate processing, where moisture content is decreased and unique flavors and texture are developed. The determination of the degree of roasting in cocoa beans is important to ensure the quality of chocolate. Determining the degree of roasting relies on human specialists or sophisticated chemical analyses that are inaccessible to small manufacturers and farmers. In this study, an electronic nose system was constructed consisting of an array of gas sensors and used to detect volatiles emanating from cocoa beans roasted for 0, 20, 30 and 40 min. The several signals were used to train a three‐layer artificial neural network (ANN). Headspace samples were also analyzed by gas chromatography/mass spectrometry (GC/MS), with 23 select volatiles used to train a separate ANN.

RESULTS

Both ANNs were used to predict the degree of roasting of cocoa beans. The electronic nose had a prediction accuracy of 94.4% using signals from sensors TGS 813, 826, 822, 830, 830, 2620, 2602 and 2610. In comparison, the GC/MS predicted the degree of roasting with an accuracy of 95.8%.

CONCLUSION

The electronic nose system is able to predict the extent of roasting, as well as a more sophisticated approach using GC/MS. © 2018 Society of Chemical Industry     

The effects of the organic acids in cocoa on the flavour of chocolate

Samples (54) of dried fermented cocoa beans from different world regions were analysed for levels of organic acids, pH and titratable acidity. The effects of the organic acids on the flavour characteristics of cocoa were examined by sensory evaluation of chocolate made from samples of cocoa beans. Concentrations (g kg^?1) of acids ranged from 1.3 to 11.8 for acetic, 1-6 to 9-9 for citric, 0.6 to 11.1 for lactic and 2.1 to 6.5 for oxalic. pH values ranged from 4.6 to 5.8, while titratable acidity ranged from 0.08 to 0.31 equivalents of sodium hydroxide per kg sample. Cocoas from South East Asia and the South Pacific tended to be more acidic than West African beans in terms of both chemical and sensory characteristics. Lactic and acetic acids were found to be in greater concentrations in cocoas from the former regions and were considered to be largely responsible for higher acid flavour scores. In contrast, citric and oxalic acids were generally lower in these beans. Flavour assessments of cocoas with and without added organic acids indicated that oxalic acid played an important role in chocolate flavour. These results suggest that a reduction in the levels of acetic and lactic acids only, may not be sufficient to produce a desirable flavour balance.     

发酵和焙烤对可可豆多酚、黄酮和风味品质的影响

本实验采用高效液相色谱仪（high performance liquid chromatography,HPLC）、色差仪、电子鼻分别检测未发酵、发酵和焙烤海南可可豆的总酚含量、总黄酮含量、色度和可可豆风味差异。结果表明：未经焙烤的未发酵豆总酚（464.03 mg/10 g）和总黄酮（126.86 mg/10 g）含量明显高于发酵豆总酚（211.86 mg/10 g）和总黄酮（61.98 mg/10 g）含量。105～145 ℃焙烤30 min,未发酵豆总酚和总黄酮含量分别为419.5～129.8 mg/10 g和77.8～16.8 mg/10 g;发酵豆总酚和总黄酮含量分别为182.53～86.25 mg/10 g和34.7～7.0 mg/10 g。其中,125 ℃焙烤20～40 min,未发酵豆总酚和黄酮含量分别为353.74～289.45 mg/10 g和42.86～32.20 mg/10 g;发酵豆总酚和黄酮含量分别为152.08～123.55 mg/10 g和25.12～21.14 mg/10 g。在105～145 ℃的温度焙烤下没食子酸含量变化显著。可可豆色度值的范围：L*值集中在40.0～47.0之间,a*值集中在5.0～6.8之间,b*值集中在4.0～8.5之间。未发酵和发酵可可豆之间,以及不同温度焙烤可可豆之间的电子感官风味分析结果差异较大。     

An improved method for the extraction and quantitation of anthocyanins in cocoa beans and its use as an index of the degree of fermentation

A method for the extraction and quantitation of anthocyanins in cocoa beans is described. The principles of the method involve extraction in dilute acid, concentration and purification by means of a disposable reverse phase column and quantitation spectrophotometrically. The method recovers >95% of anthocyanins in the acid extract and has an average coefficient of variation of 12%. Results are presented for the effects of time of fermentation and the time of fermentation plus drying on the anthocyanin content of cocoa beans. Cut test results and anthocyanin assay results are presented for commercial samples of different origins.     

Dark chocolate acceptability: influence of cocoa origin and processing conditions

BACKGROUND: Chocolate properties can vary depending on cocoa origin, composition and manufacturing procedure, which affect consumer acceptability. The aim of this work was to study the effect of two cocoa origins (Ghana and Ecuador) and two processing conditions (roasting time and conching time) on dark chocolate acceptability. RESULTS: Overall acceptability and acceptability for different attributes (colour, flavour, odour and texture) were evaluated by 95 consumers. Differences in acceptability among dark chocolates were mainly related to differences in flavour acceptability. The use of a long roasting time lowered chocolate acceptability in Ghanaian samples while it had no effect on acceptability of Ecuadorian chocolates. This response was observed for most consumers (two subgroups with different frequency consumption of dark chocolate). However, for a third group of consumers identified as distinguishers, the most acceptable dark chocolate samples were those produced with specific combinations of roasting time and conching time for each of the cocoa geographical origin considered. CONCLUSION: To produce dark chocolates from a single origin it is important to know the target market preferences and to select the appropriate roasting and conching conditions. Copyright © 2011 Society of Chemical Industry     

Changes of phenolic compounds and antioxidant capacity in cocoa beans processing

A number of studies have shown that the consumption of cocoa and chocolate products has positive health effects on humans. The object of this research was to monitor changes of total and individual phenolics and antioxidant capacity during the cocoa bean manufacturing. The loss of cocoa phenolics and their antioxidant activity vary with the degree of technological process. The process of roasting and cocoa nib alkalisation had the major influence on phenolic compounds as well as on antioxidant capacity. The roasting treatment resulted in 14% loss of the total phenolics content, while alkalisation resulted in 64% loss of total phenolics content. Procyanidins B1 and B2 as well as (?)‐epigallocatechin were the unstable components, while caffeic acid derivate showed the greatest stability in all technological process. Furthermore, PCA showed that phenolic contents, antioxidant capacity and non‐fat cocoa solids parts of the samples were classified in groups according technological conditions.     

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.     

Food Evolution: The Impact of Society and Science on the Fermentation of Cocoa Beans

Cocoa is part of the cultural heritage in many areas of South and Central America and has played an important role in the history of human culture there. The modern methods of cocoa bean production for the purpose of the manufacture of modern chocolate are tied to the origin and development of cocoa bean fermentation and processing methods and the science of microbiology. To date, however, there has not been a study that discusses the impacts of both science and culture on the evolution of cocoa beans and cocoa bean processing. This work provides both a detailed overview of the evolution and historical development of cocoa, from its earliest forms to modern chocolate manufacturing, an in‐depth discussion of the biochemistry of cocoa bean fermentation, as well as a compilation of primary research studies with details on fermentation methods, the scientific bases of interactions in microbial fermentations, and methods for their investigation, as well as metabolites that are produced. As a result, we present here the major microorganisms among all the ones that have been identified in previous studies. This database will aid researchers seeking standardized inoculants to drive cocoa bean fermentation, as well as serve as a guide for inventorying and assessing other food evolution–related studies regarding traditional and artisanal‐based food systems.     

Effects of incubation and polyphenol oxidase enrichment on colour, fermentation index, procyanidins and astringency of unfermented and partly fermented cocoa beans

Incubation of unfermented and partly fermented cocoa beans in acetate buffer, pH 5.5, at 45 °C increased yellowness, total colour differences and fermentation index value of the cocoa bean powders and decreased cocoa procyanidins (monomers to pentamers), and their astringency. Fermentation index and (–)‐epicatechin content, equivalent to those of fully fermented beans, were reached by unfermented beans after 4–8‐h incubation, but not by partly fermented beans even after 16 h. During incubation of partly fermented cocoa beans enriched with polyphenol oxidase, yellowness and fermentation index value were increased, whilst (–)‐epicatechin was decreased. Tyrosinase had a less significant effect in yellow colour formation, but showed a significant reduction of (–)‐epicatechin and increase in fermentation index compared with crude cocoa polyphenol oxidase. However, both enzymes have similar effects on procyanidin degradation and astringent taste reduction. Incubation of cocoa beans for 16 h increased the cut test score of unfermented and partly fermented beans by 50 and 30%, respectively.     

Monitoring of cocoa volatiles produced during roasting by selected ion flow tube-mass spectrometry (SIFT-MS)

Selected ion flow tube-mass spectrometry (SIFT-MS) was used to measure the real-time concentrations of cocoa volatiles in the headspace during roasting. Alkalized and unalkalized Don Homero and Arriba cocoa beans were roasted at 120, 150, and 170 °C in a rotary roaster. The concentrations of total alcohols, acids, aldehydes, esters, ketones, and alkylpyrazines increased, peaked, and decreased within the timeframe used for typical roasting. The concentrations of alkylpyrazines and Strecker aldehydes increased as the roasting temperature increased from 120 to 170 °C. For most of the volatile compounds, there was no significant difference between Arriba and Don Homero beans, but Arriba beans showed higher concentrations of 2-heptanone, acetone, ethyl acetate, methylbutanal, phenylacetaldehyde, and trimethylpyrazine. For unalkalized Don Homero beans (pH 5.7), the time to peak concentration decreased from 13.5 to 7.4 min for pyrazines, and from 12.7 to 7.4 min for aldehydes as the roasting temperature increased from 120 to 170 °C. Also, at 150 °C roasting, the time to peak concentration was shortened from 9 to 5.1 min for pyrazines, and from 9.1 to 5 min for aldehydes as the pH increased from 5.7 to 8.7. PRACTICAL APPLICATION: SIFT-MS allows for real-time monitoring of the key volatile compounds contributing to chocolate flavor, with minimal sample preparation, thus can be used to facilitate adjusting the roasting conditions, such as temperature and time, to optimize chocolate flavor during roasting. Real-time monitoring during roasting can also be used to evaluate the flavor quality of different types of beans by comparing the concentrations of key flavor compounds.     

Effect of post-harvest treatments on the occurrence of ochratoxin A in raw cocoa beans

Cocoa beans are the principal raw material for chocolate manufacture. Moulds have an important place in the change in the quality of cocoa beans due to their role in the production of free fatty acids and mycotoxins, namely ochratoxin A (OTA). This study investigated the impact of the key post-harvest treatments, namely the fermentation and drying methods on OTA contamination of raw cocoa beans. Analytical methods for OTA detection were based on solid–liquid extraction, clean-up using an immunoaffinity column, and identification by reversed-phase HPLC with fluorescence detection. Of a total of 104 randomly selected cocoa samples analysed, 32% had OTA contents above 2 µg kg^–1. Cocoa sourced from pods in a bad state of health had a maximum OTA content of 39.2 µg kg^–1, while that obtained from healthy pods recorded 11.2 µg kg^–1. The production of OTA in cocoa beans increased according to the pod-opening delay and reached 39.2 µg kg^–1 after an opening delay of 7 days after harvest, while 6.1 and 11.2 µg kg^–1 were observed when pods were opened after 0 and 4 days. OTA production also seemed to depend considerably to the cocoa fermentation materials. When using plastic boxes for bean fermentation, the OTA production was enhanced and reached an average OTA content of about 4.9 µg kg^–1, while the raw cocoa treated in banana leaves and wooden boxes recorded 1.6 and 2.2 µg kg^–1 on average respectively. In parallel, the OTA production was not really influenced by either the mixing or the duration of the fermentation or the drying materials.     

Ghanaian Cocoa Bean Fermentation Characterized by Spectroscopic and Chromatographic Methods and Chemometrics

Abstract: Export of cocoa beans is of great economic importance in Ghana and several other tropical countries. Raw cocoa has an astringent, unpleasant taste, and flavor, and has to be fermented, dried, and roasted to obtain the characteristic cocoa flavor and taste. In an attempt to obtain a deeper understanding of the changes in the cocoa beans during fermentation and investigate the possibility of future development of objective methods for assessing the degree of fermentation, a novel combination of methods including cut test, colorimetry, fluorescence spectroscopy, NIR spectroscopy, and GC-MS evaluated by chemometric methods was used to examine cocoa beans sampled at different durations of fermentation and samples representing fully fermented and dried beans from all cocoa growing regions of Ghana. Using colorimetry it was found that samples moved towards higher a* and b* values as fermentation progressed. Furthermore, the degree of fermentation could, in general, be well described by the spectroscopic methods used. In addition, it was possible to link analysis of volatile compounds with predictions of fermentation time. Fermented and dried cocoa beans from the Volta and the Western regions clustered separately in the score plots based on colorimetric, fluorescence, NIR, and GC-MS indicating regional differences in the composition of Ghanaian cocoa beans. The study demonstrates the potential of colorimetry and spectroscopic methods as valuable tools for determining the fermentation degree of cocoa beans. Using GC-MS it was possible to demonstrate the formation of several important aroma compounds such 2-phenylethyl acetate, propionic acid, and acetoin and the breakdown of others like diacetyl during fermentation. Practical Application: The present study demonstrates the potential of using colorimetry and spectroscopic methods as objective methods for determining cocoa bean quality along the processing chain. Development of objective methods for determining cocoa bean quality will be of great importance for quality insurance within the fields of cocoa processing and raw material control in chocolate producing companies.     

纯脂巧克力用脂及其分析、应用研究进展

近年来纯脂巧克力日渐受欢迎,但可可原料面临产量有限且不稳定的制约因素,限制了纯脂巧克力的发展。作为与可可脂组分及特性最为接近的可可脂替代品,类可可脂的原料来源广泛,产品稳定性有提升空间,并且在提升纯脂巧克力品质方面有改善作用,因此类可可脂的相关研究也获得国内外广泛关注。通过对可可脂及类可可脂的组成、结晶特性、分析方法及纯脂巧克力的耐霜、抗热品质改善等方面进行综述,以期对纯脂巧克力用脂、巧克力品质改善等提供相关参考。     

低热量巧克力制品的研究进展

从低可可脂用量巧克力的制备、低热量可可脂替代物的开发和低热量甜味剂替代蔗糖的研究3个方面论述了低热量巧克力制品的研究进展。主要涉及了结构化甘油三酯、功能性甘油二酯和碳水化合物基脂肪替代品等可可脂的低热量替代物的性质及其应用于巧克力制品中对流变性能、工艺特性等的影响,以期为低热量巧克力的研究与生产提供参考。     

Protective effect of polyphenol‐rich extract prepared from Malaysian cocoa (Theobroma cacao) on glucose levels and lipid profiles in streptozotocin‐induced diabetic rats

BACKGROUND: Cocoa beans are used for preparing cocoa liquor and cocoa powder, which are the main ingredients of cocoa‐based products. Previous studies have reported the health benefits of cocoa polyphenols in reducing the risk of cardiovascular diseases. However, there is no report on the efficacy of cocoa polyphenols on diabetes mellitus. Therefore this study was designed to evaluate the protective effect of cocoa polyphenol‐rich extract (CE) on glucose levels and lipid profiles in streptozotocin (STZ)‐induced diabetic rats. Male Sprague‐Dawley rats were divided into diabetic control, diabetic CE and diabetic glibenclamide groups. RESULTS: Three different dosages of CE (10, 20 and 30 mg per 100 g body weight) were administered orally once a day for 1 week before STZ injection and for 3 weeks thereafter. The results showed that CE could normalise the body weight loss caused by STZ. In the 20 mg CE‐pretreated group there was a 143% increase in plasma glucose levels, compared with a 226% increase in diabetic control rats. CE could also normalise total cholesterol, triglycerides and high‐density lipoprotein cholesterol at the end of the experiment compared with the baseline. CONCLUSION: The present study suggests that pretreatment with CE from roasted cocoa beans could prevent the development of diabetes induced by STZ injection in rats. Copyright © 2008 Society of Chemical Industry