Impact of starter cultures and fermentation techniques on the volatile aroma and sensory profile of chocolate

The sensory quality of chocolate is widely determined by the qualitative and quantitative composition of volatile compounds resulting from microbial metabolism during fermentation, and Maillard reactions taking place during drying, roasting and conching. The influence of applying mixed starter cultures on the formation of flavour precursors, composition of volatile aroma compounds and sensory profile was investigated in cocoa inoculated with cultures encompassing a highly aromatic strain of Pichia kluyveri or a pectinolytic strain of Kluyveromyces marxianus, and compared to commercially fermented heap and tray cocoa. Although only minor differences in the concentration of free amino acids and reducing sugars was measured, identification and quantification by dynamic headspace gas chromatography–mass spectrometry (HS/GC–MS) revealed pronounced differences in the composition of volatiles in roasted cocoa liquors and finished chocolates. 19 of the 56 volatile compounds identified in the chocolates were found in significantly higher amounts in the tray fermented sample, whilst significantly higher amounts of 2-methoxyphenol was measured in the two inoculated chocolates. The P. kluyveri inoculated chocolate was characterized by a significantly higher concentration of phenylacetaldehyde and the K. marxianus inoculated chocolate by significantly higher amounts of benzyl alcohol, phenethyl alcohol, benzyl acetate and phenethyl acetate compared to a spontaneously fermented control. Sensory profiling described the heap and tray fermented chocolates as sweet with cocoa and caramel flavours, whilst the inoculated chocolates were characterized as fruity, acid and bitter with berry, yoghurt and balsamic flavours. The choice of fermentation technique had the greatest overall impact on the volatile aroma and sensory profile, but whilst the application of starter cultures did affect the volatile aroma profile, differences were too small to significantly change consumer perception of the chocolates as compared to a spontaneously fermented control.     

Evaluation of chocolate as a source of dietary copper

Chocolate has frequently been proposed to be a valuable source of dietary copper, but data on the copper content of major contemporary chocolate brands are scarce. The copper content of 22 brands of chocolate, many of which are sold worldwide, is thus presented here. A reliable hot ashing procedure to determine the copper content of chocolate by inductively coupled plasma atomic emission spectroscopy is also described. It was found that the copper contents of the chocolates analyzed here varied in the range of 1.85 ± 0.10 to 16.50 ± 1.29 μg/g. There was a linear correlation of the copper content of chocolate to its cocoa content with a correlation coefficient R ² of 0.89, showing that the copper was largely contributed to the chocolate by the cocoa. The value of chocolate as a source of dietary copper is discussed.     

An investigation on the appropriateness of chocolate to match tea and coffee

The aim of this study was to provide some recommendations for selecting a befitting tea and coffee to match chocolate with different cocoa contents. Three coffee samples (chocolate flavored, vanilla flavored and unflavored coffee), four tea samples (black tea, green tea, vanilla flavored tea and citrus flavored tea) and three chocolates (30%, 70%, and 99% cocoa) were hedonically rated by eighty regular chocolate consumers. The beverages were then paired with each chocolate, and the consumers were asked to indicate the hedonic liking of the resulting pairings, and to indicate whether the chocolate or beverage flavor dominated the pairing flavor. This study showed that liking of chocolate and coffee pairings and chocolate and tea pairings significantly varied (p < 0.001) across samples. Consumers preferred pairings with 30% cocoa and 70% cocoa chocolate to pairings with 99% cocoa chocolate. Overall, coffee is significantly (p < 0.001) preferred to tea as a chocolate partner.Chocolate and beverage pairing liking was biased by the liking of the beverage tasted alone, the liking of chocolate tasted alone, beverage type, chocolate type and the level of flavor match between chocolate and tea or coffee in a given pairing. When chocolate and beverage flavor balanced out in a given pairing, chocolate and coffee/tea pairings were significantly preferred by the consumers. A significant decrease in acceptance was observed when beverage or chocolate flavor dominated the flavor of the pairing, much more so when the chocolate flavor dominated the pairing flavor. However consumers don't enjoy any preferred chocolate with any preferred tea or coffee because some flavors match better than do others. Indeed, consumers formulate their hedonic responses taking into consideration what flavors go well together more than they rely exclusively on their hedonic judgments of the chocolates, the teas, and the coffees tasted alone.     

Assessing the shapes and speech sounds that people associate with chocolate samples varying in cocoa content

We report a series of three experiments designed to highlight the reliable crossmodal correspondences that exist between the cocoa content of various commercially-available chocolate products and both visually-presented shapes and nonsense words. The chocolates tested in this study included three kinds of Lindt chocolate and a milk chocolate truffle (‘Koko’ brand from Cadbury). Participants were given paper-based line scales, anchored at either end with either a nonsense word or simple outline shape. They tasted the chocolates and indicated whether their perception of the flavor better matched one or other of the items anchoring the scales by marking the appropriate point along the scale. The results demonstrate that certain chocolates were more strongly associated with angular shapes and ‘sharp’ inflected, high-pitched meaningless words, such as ‘tuki’ and ‘takete’. Specifically, Lindt extra creamy milk chocolate (30% cocoa) and Cadbury’s Koko milk chocolate truffles were both more strongly associated with rounded shapes and softer sounding, lower-pitched pseudo-words, such as ‘maluma’. By contrast, Lindt 70% and 90% cocoa chocolates were more strongly associated with sharper (angular) shapes and sounds, such as ‘takete’. These results demonstrate that the phenomenon of sound symbolism extends beyond the visual modality into the domain of flavor perception where, in particular, speech sounds carry meaning in terms of the taste/flavor of chocolates. These results have implications for the development of novel brand names for new products (such as, in this case, chocolate) that best connote the product’s likely sensory attributes.     

Factors contributing to the variation in the volatile composition of chocolate: Botanical and geographical origins of the cocoa beans,and brand-related formulation and processing

The intrinsic characteristics of chocolate and the complex technological process complicate the assessment of the typical features of this product and the verification of its authenticity. In this study, the influence of the botanical and geographical origin of the cocoa beans, as well as the impact of brand-related processing on the volatile organic compound (VOC) composition of the resulting chocolates was examined. A total of ninety dark chocolates available on the Dutch market were analysed using Proton-Transfer-Reaction-Mass Spectrometry (PTR-MS). The VOC profiles generated by PTR-MS (136 masses per sample) were used as fingerprints and investigated using chemometric tools to elucidate information on production factors of cocoa and subsequent processing, in the finished product. Principal component analysis (PCA) showed some clustering of the chocolates according to the botanical and geographical origins of beans as well as according to the brand. Partial least square discriminant analysis (PLS-DA) further discriminated the samples according to the three classes (botanical origin, geographical origin, brand) and the models with the best classification results were used to investigate the relevant masses for each class. PCA clustering and PLS-DA classification highlighted that chocolate profiles are strongly affected by the processing applied by the different brands. However, reflection of the botanical and geographical origins of the beans was also mirrored in the VOC composition of the chocolates. PTR-Time of Flight-MS (PTR-ToF-MS) was used to tentatively identify the VOCs of the chocolates. These measurements allowed the identification of 36 spectrometric peaks which relate to the main classes of chocolate odorant compounds, in particular, aldehydes and pyrazines, products of Maillard reactions. Several compounds already present in unroasted beans were tentatively identified in the chocolates as well, such as, acetic acid, methylpropanoic acid, 2- and 3-methylbutanoic acid, 2-phenylethanol, and tetramethylpyrazine. The results of this study emphasize the impact of the brand-related formulation and processing on VOC profiles of dark chocolates. However, using chemometrics, VOC reflection of the botanical origin and geographical origin of the beans in the chocolates was revealed, which may be useful for a future cocoa/chocolate traceability.     

Effect of cocoa butter replacement with a β‐glucan‐rich hydrocolloid (C‐trim30) on the rheological and tribological properties of chocolates

BACKGROUND: The food industry has been facing the challenge of developing low‐fat and low‐calorie food products due to rising health awareness of consumers. To meet this consumer demand, an oat β‐glucan‐rich hydrocolloid (C‐trim30) was evaluated as a cocoa butter substitute in chocolates. The effects of C‐trim30 on the rheological, tribological, and textural properties of chocolates were investigated. RESULTS: The viscosity of molten chocolates increased with increasing levels of C‐trim30. Flow behaviors analyzed using the Casson model showed that the Casson viscosity and yield stress increased with increasing concentration of C‐trim30 in the chocolate. Tribological tests on a ball‐on‐flat tribometer showed a reduction in boundary coefficients of friction, with increasing C‐trim30. In addition, hardness of chocolates showed that replacement of cocoa butter with C‐trim30 produced chocolates with softer texture. CONCLUSIONS: The cocoa butter replacement with C‐trim30 up to 10% produced soft chocolates with improved boundary lubrication properties. Also, the chocolate prepared by replacing the cocoa butter with C‐trim30 resulted in a product with a lower caloric value and increased health benefits from the oat β‐glucan. Copyright © 2008 Society of Chemical Industry     

Structural characteristics of cocoa particles and their effect on the viscosity of reduced fat chocolate

Aimed at the manufacture of reduced fat chocolates, a novel method of trapped fat reduction was assessed: Manipulation of the cocoa ingredient. Cocoa mass was replaced with cocoa powder (11 g/100 g or <1 g/100 g fat) and added ‘free’ cocoa butter. A cocoa solids approach to design reduced fat chocolates with satisfactory flow properties is attractive to industry since it circumvents introduction of ingredients not commonly used in chocolate manufacture. Results showed that the cocoa mass chocolate had a higher viscosity than cocoa powder chocolates of the same total fat content due to the presence of trapped fat globules as identified by confocal laser scanning microscopy. The chocolate prepared with standard defatted cocoa powder containing 11 g/100 g fat had a lower viscosity than the chocolate containing highly defatted cocoa powder (<1 g/100 g) due to particle shape and fat diffusion into the particles as revealed by microscopy analyses. Based on the evidence presented, it can be concluded that standard defatted cocoa powder, as widely used by the industry, is indeed the best compromise in terms of free fat, particle size and morphology attempting to formulate fat reduced chocolate of acceptable molten state viscosity.     

Use of Palm Mid-Fraction in White Chocolate Formulation

Samples of two types of palm mid-fraction (PMF I, a commercial sample and PMF II, from a laboratory-scale acetone fractionation of PMF I) and a Malaysian deodorised cocoa butter sample were used as the main components in the fat phase for white chocolate formulation. The monounsaturatedtriacylglycerol contents of these fats were 853, 899 and 903 g kg⁻¹, respectively.All the fats had free fatty acid contents of less than 10 g kg⁻¹ and melting points in the range of 34·0–34·5°C. The solid fat content profiles for the three fats were very steep. Differential scanning calorimeter analyses showed that all the fats had two melting peaks, T1 and T2. Results of the study showed that the tempering time to produce a well-tempered chocolate using PMF I was longer than that using PMF II, whereas, the time to produce a well-tempered cocoa butter chocolate increased with increase in the tempering temperature. Chocolates made with PMF I and II were well tempered between 17 and 19°C and with cocoa butter at 23°C. Thermal analyses, carried out on the chocolate showed that PMF I and II produced three melting peaks, T1, T2′ and T2 whereas most of the cocoa butter chocolates exhibited only one melting peak, T2. Storage studies showed that most of the chocolates had good bloom resistance for up to 12 weeks storage.     

Properties of sucrose-free chocolates enriched with viable lactic acid bacteria

Chocolate formulated with isomalt and enriched with lactic acid bacteria Streptococcus thermophilus MK-10 and Lactobacillus delbrueckii subsp. bulgaricus 151, added in the form of powdered yoghurt, prepared by spray-drying is a sucrose-free, low-calorie product with functional properties. The technique of the production of chocolate sweetened with isomalt and containing live cells of the aforementioned bacterial strains has been established. Physicochemical and sensory properties of this product as well as survival of cells during 6-months storage at 4 and 18 °C have been determined. The isomalt-containing yoghurt chocolates displayed satisfactory sensory attributes. Their calorific value and consistency (hardness) were similar to those of control sucrose-free chocolates. The total acidity of yoghurt and standard milk chocolates was also similar, whereas yoghurt-containing dark chocolates displayed higher acidity. The characteristics of yoghurt-containing chocolates were a relatively low solid substance content (96.82–96.91% w/w), low Casson viscosity and yield value for milk chocolate masses, and enhanced rheological parameters for dark chocolate masses compared with control sucrose-free chocolates. Because the total number of lactic acid bacteria after 6-months storage at 4 and 18 °C was high (approximately 10⁷ cfu/g), the sucrose-free yoghurt-containing chocolates can be regarded as functional foods.     

Investigation of chocolate produced from four different Brazilian varieties of cocoa (Theobroma cacao L.) inoculated with Saccharomyces cerevisiae

Properly conducted cocoa fermentation is an important step for the production of high-quality chocolate. The aim of this work was to investigate the effect of four cocoa varieties (CCN51, PS1030, FA13, and CEPEC 2004) inoculated with Saccharomyces cerevisiae CA11 on microbial communities and the profile of volatile compounds and sensory characteristics of chocolate. The S. cerevisiae population increased significantly (p < 0.05) during the fermentations. The microbial communities varied according to cocoa variety fermentation as assessed by denaturing gradient gel electrophoresis (DGGE). The dominant yeasts were S. cerevisiae and Hanseniaspora guilliermondii, while Lactobacillus casei and Gluconobacter oxidans were the predominant bacteria in the four different fermentations analyzed. Sixty-one volatile compounds—including aldehydes (11), ketones (10), esters (14), acids (8), alcohols (8), pyrazines (5), furans (3), and others (caffeine and heptadecane)—were detected and quantified by GC–MS in the different chocolates. The sensory analysis showed that caramel was perceptible in the chocolate of PS1030, while CEPEC2004 was related to astringency, bitterness, and chocolate flavor attributes. The chocolates produced from FA13 and CCN51 were more similar in terms of sour and chocolate aroma. A “temporal dominance of sensation” (TDS) analysis showed that although the bitter attribute was dominant, the fruity, sweet, sour, astringent, and cocoa attributes were also perceptible, depending on the cocoa variety. These results suggest that the cocoa varieties had an influence on the chocolate's quality, which should be considered to obtain chocolate with different sensory characteristics or for better standardization of the process, even when using yeast as a starter culture.     

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     

Effects of fat replacement and fibre addition on the texture,sensory acceptance and structure of sucrose‐free chocolate

Dietary fibre has been employed as a sucrose and fat replacement in chocolates and can influence the physical and sensory characteristics of the resulting product. Formulations of sucrose‐free chocolates were developed with the addition of inulin and β‐glucan concentrate as partial substitutes for cocoa butter using a mixture design. The effects of the combinations of the three ingredients provided for the design on the texture, microstructure and sensory acceptance of the chocolates were investigated. The substitution of cocoa butter for inulin or β‐glucan concentrate decreased the hardness of the chocolates. It was possible to replace 10 g of cocoa butter in a 100‐g control formulation with inulin and still maintain good acceptance, while this same substitution with β‐glucan resulted in less acceptable chocolate, with a mean score of 6.4 on a scale from 0 to 10. Scanning electron microscopy (SEM) was used to investigate the effects of fibre addition by observing the developed microstructure.     

A micromechanical based finite element model approach to accurately predict the effective thermal properties of micro-aerated chocolate

Micro-aeration is a method to modify the sensorial attributes of chocolate but also affects the material properties of chocolate, which in turn, determine its material response during manufacturing and oral processes. This study aims to define the effect of micro-aeration on the thermal properties of chocolate by considering the changes of chocolate microstructure due to micro-aeration. Micro-aeration was found to alter the chocolate microstructure creating a layer of a third phase at the porous interfaces, which is argued to consist of cocoa butter of higher melting properties. A multiscale Finite Element Model is developed, which was confirmed by macroscale heat transfer measurements, to parametrically simulate the structural changes of micro-porous chocolates at the microscale level and estimate their effective properties, such as thermal conductivity and specific heat capacity. The developed multiscale computational model simulates the porous chocolate as a two-phase (chocolate- pores) or three-phase material (chocolate-cocoa butter layer- pores). The investigation identified a new, complex transient thermal mechanism that controls the behaviour of micro-aerated chocolate during melting and solidification. The results showed a maximum 13% reduction of k_eff and 15% increase of C_peff with 15% micro-aeration resulting to a slower transient heat transfer through the micro-aerated chocolate. The reason is that the micro-aerated chocolate can store a larger amount of thermal energy than its solid counterpart. This effect slows down the transient heat transfer rate in the chocolate and modifies melting/solidification rate and impacts sensorial attributes during oral processing and cooling during manufacturing.     

Solid Fat Content,Pre-Crystallization Conditions,and Sensory Quality of Chocolate with Addition of Cocoa Butter Analogues

The objective of this study was to determine how the addition of two cocoa butter equivalents and cocoa butter improver affect the physical and sensory properties of chocolate. The laboratory-made chocolate samples were tempered at three different pre-crystallization temperatures (25, 27, and 29°C), using different concentrations (3, 5, and 7%) of two commercial cocoa butter equivalents as well as commercial cocoa butter improver of the chocolate. The nucleation time of the chocolate mass primarly depended on pre-crystallization temperature while the value of maximum torque of chocolate mass were influenced by both, pre-crystallization temperature and concentration of fats. Sensory evaluation revealed that cocoa butter equivalents were acceptable in chocolate formulation without producing a negative impact on the sensory quality, while usage of improver required adjustment of raw formulations or process parameters. The results of the instrumentally measured hardness revealed that addition of cocoa butter improver significantly (p > 0.05) increased hardness of chocolate samples.     

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.     

Combination of the Simple Additive (SAW) Approach and Mixture Design to Determine Optimum Cocoa Combination of the Hot Chocolate Beverage

Physicochemical (pH, brix, and color), sensory (color, taste, odor, mouthfeeling, consistency, bitter flavor, and general acceptability), and rheological properties of the hot chocolate beverages including different cocoa combinations were investigated in the present study. Cocoa type significantly affected all of the properties. Simple additive weighting approach was applied to obtain one score from seven different sensory parameters and simple additive weighting score was used in mixture design to determine optimum cocoa type or cocoa combination. Ostwald de Waele model described the flow behavior of the hot chocolate beverage samples with R² values ranged between 0.818 and 0.999. The consistency coefficient (K) and apparent viscosity at shear rate 50 s^?1 (η₅₀) were significantly affected by cocoa type found in the formulation of the beverage. The mixture design approach was performed in order to determine variation of the responses (physicochemical, sensory, and rheological parameters) as a function of cocoa concentration. Simple additive weighting scores were satisfactorily described by established equation as a function of cocoa concentration to be used in the formulation of the hot chocolate beverage (R² = 0.8645).     

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     

Fat Bloom and Chocolate Structure Studied by Mercury Porosimetry

The structure of dark chocolate samples was analyzed by mercury porosimetry in order to determine whether the formation of fat bloom was related to the presence of pores. The influence of cocoa butter concentration and tempering conditions on porosity were determined by using samples containing 29.5 or 31.9% fat, which were under, well or over-tempered. All Mercury porosimetry analysis confirmed the presence of a porous structure in all chocolates. Empty spaces represented about 1% of the whole volume of a well-tempered chocolate containing 31.9% cocoa butter but made up about 4% of the over-tempered chocolate. A well-tempered chocolate with only 29.5% cocoa butter showed the presence of about 2% empty spaces. From these observations and gas permeability a possible model for the microscopic structure was developed.