Linalool contents as characteristic of some flavor grade cocoas

Summary The terpenes present in cocoa flavour were analysed by means of gas chromatography-mass spectrometry. The pyranoid linalool oxides, ocimene and nerolidol, were identified for the first time as cocoa volatiles. Linalool, which is the major terpene component in cocoa contributes markedly to the flowery and tea-like flavour of some cocoa varieties. Flavour grade beans contain relatively high concentrations of linalool and basic grade cocoas possess. The isolation of linalool by means of intensive (simultaneous distillation extraction) and more gentle methods (vacuum condensation) yields similar quantitative results. The estimation of the concentration ratio of linalool/benzaldehyde within steam distillates ist suitable for the industrial quality control of unroasted cocoas.

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Linaloolgehalt als Merkmal einiger Edelkakaos

Zusammenfassung In Kakaoaroma wurden anhand GC/MS einige Terpene nachgewiesen, darunter erstmals auch die pyranoiden Linalooloxide, Ocimen und Nerolidol. Linalool als Hauptkomponente dieser Gruppe trägt wesentlich zum blumigen und tee-artigen Aroma einiger Kakaosorten bei. Edelkakaos weisen relativ hohe, Konsumkakaos niedrige Linalool-Konzentrationen auf. Die Isolierung von Linalool unter drastischen (simultane Destillation Extraktion) und milden Bedingungen (Vakuum-Kondensation) liefert ähnliche quantitative Ergebnisse. Die Bestimmung des Konzentrationsverhältnisses von Linalool/Benzaldehyd in Wasserdampfdestillaten eignet sich zur industriellen Qualitätskontrolle von Rohkakao.

     

Amadori-Verbindungen als Aromavorstufen in Kakao

Amadori-compounds as cocoa aroma precursors Several Amadori-compounds (fructose-amino acids), important intermediates of Maillard reaction, have been found in unroasted cocoa beans some years ago. Now, in cocoa additional fructose-phenylalanine (fru-phe) could be detected by means of a modified extraction procedure. For studying the contribution of Amadori-compounds fru-phe and fru-leu (fructose-leucine) were roasted at 145°C. The roasted flavours contained a lot of key compounds of cocoa flavour. If cocoa was moist-thermally treated and dried the level of Amadori-compounds could be raised and the roasted aroma intensified. Amadori-compounds obviously contribute to flavour formation in cocoa. This effect may by used technologically to increase flavour yield.     

Analysis and stereodifferentiation of linalool in Theobroma cacao and cocoa products using enantioselective multidimensional gas chromatography

Contents and enantiomeric distributions of linalool (3,7-dimethyl-1,6-octadien-3-ol) were investigated in raw and roasted cocoa beans (seeds of Theobroma cacao) of defined origin as well as in commercial products, such as cocoa powders or chocolates. The stereodifferentiation of linalool was achieved by enantioselective multidimensional gas chromatography using heptakis (2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as chiral stationary phase. Simultaneous steam distillation–extraction at pH 7 allowed sample preparation without racemization of linalool. Cocoa beans contain linalool primarily as (S)-enantiomer. Model experiments and analyses of commercial products such as cocoa powders and chocolates revealed that technological procedures employed in the manufacturing of cocoa products do not result in significant changes of the original enantiomeric distribution of linalool.     

Application of various methods for determination of the color of cocoa beans roasted under variable process parameters

Cocoa beans of Forastero variety from Togo were subjected to roasting under either constant or variable process parameters. The variable process parameters were roasting air flow rate, temperature and relative humidity. The color of roasted cocoa beans was determined by pigment extraction under various conditions followed by either their spectrophotometric assays or CIE L*a*b measurements. Also the Maillard compounds index and total polyphenols content correlated with progress of the browning of beans were determined. It was found that an increase in the roasting air relative humidity stimulated formation of brown pigments, while elevated temperature caused worsening of color parameters of roasted cocoa beans. The most suitable method of color characterization of roasted cocoa beans was found to be pigments extraction combined with either separation of their fractions or CIE L*a*b measurements. These assays revealed that cocoa beans roasted under variable roasting air flow rate were characterized by improved color parameters. The relatively simple and inexpensive CIE L*a*b measurements ensured fast analysis of color parameters, while total polyphenols in roasted cocoa beans were quickly estimated by using F–C reagent. Furthermore, quantification of melanoid pigments in roasted cocoa beans can be based on determination of the index of nonenzymatic browning products content, which is relatively simple and inexpensive.     

Detection and quantification of cocoa butter equivalents in chocolate model systems: analysis of triglyceride profiles by high resolution GC

The detection of vegetable fats added to cocoa butters in chocolate formulations was investigated in model mixtures. Cocoa butters varying in origins, crop and treatment were analysed alone and combined at levels of 5, 10, 15 or 20% to a variety of cocoa butter equivalents. Triglyceride profiles were obtained by high resolution GC. The areas of the major triglycerides present were plotted one vs the other. The plots of percentages of specific triglycerides allowed detection of vegetable fats added to cocoa butters in these model systems, and quantification of the addition could be done down to a 5% level on a cocoa butter basis. The detection was most difficult in the case of the addition of illipe fat and the quantification could not be done below 10%. The results suggest that, in chocolate, which contains 20–25% cocoa butter, this detection system works down to 1–2%, and thus well below the proposed 5% regulatory level. ©     

Antioxidant Properties of Cocoa Beans (Theobroma cacao L.): Influence of Cultivar and Roasting Conditions

Effects of various roasting conditions on antioxidant properties of five Theobroma cacao L. varieties were investigated. The cocoa beans were roasted at four different temperatures (110–150°C) and three different air humidities (0.3–5.0%). The raw cocoa beans were characterized by high antioxidant activities. The antioxidant properties of the roasted cocoa beans varied markedly among the analyzed cultivars and geographical regions and were affected by roasting conditions. Generally, cocoa beans of the cv. Forastero from Brazil exhibited higher total phenolic content, free radical scavenging activity, and metal chelating ability than samples of the other analyzed cocoa varieties. Roasting at 110°C caused negligible changes in total phenolics content and antioxidant activity of cocoa beans, while almost all samples tended to have lower antioxidant potential when roasting temperature increased. The air humidity used in roasting did not affect the total phenolics content and antioxidant activity for lowest roasting temperature (110°C). Moreover, the obtained results revealed that thermal processing at the higher temperatures and elevated air humidity resulted in the higher antioxidant capacities. It was also found that the ferrous ion chelating activity of cocoa beans increased with the roasting temperature (in the range from 110 to 150°C), with the exception of cv. Trinitario from Papua New Guinea. The data showed that roasting at lower temperatures with humid air are more favorable in terms of preserving the bioactivity of roasted cocoa beans.     

Tocopherols in cocoa butter obtained from cocoa bean roasted in different forms and under various process parameters

Obtaining good quality chocolate strongly depends on raw material, i.e. cocoa beans. The processing of cocoa beans consists of some important steps, including fermentation, drying fermented beans and roasting. Traditionally roasting is performed on whole beans but currently, roasting crushed cocoa beans or cocoa liquor becomes more and more popular. Many biologically active compounds may be found in the cocoa beans, including tocopherols. This work investigates the influence of the constant or variable roasting process parameters (temperature, velocity and relative humidity of roasting air) on the tocopherol concentration in cocoa butter (CB) extracted from cocoa beans originating from Togo and roasted in two different forms, namely as whole and crushed beans. Whole cocoa beans were roasted to a 2% moisture content and crushed cocoa beans were firstly partially dried which further enables easier dehusking, then ground, dehusked and roasted until their humidity decreased to around 2%. Roasting resulted in lowering the content of individual tocopherols in analyzed material. The degree of degradation of tocopherols in CBs was different, depending on the form of roasted beans from which these CBs were extracted. Higher concentrations were determined in CBs extracted from beans roasted in the form of crushed samples comparing to CBs obtained from beans roasted as a whole. The study investigates different roasting parameters of crushed beans, none of which drastically lowered the concentration of tocopherols in extracted CBs. Their concentration in CBs extracted from whole beans was, on the other hand, influenced by roasting air parameters. In case of whole beans roasted under constant parameters, application of 150 °C proved to be more favorable than roasting at 135 °C, as well as application of “dry” air and 1 m/s roasting air velocity. Discussing the variable roasting process parameters, in case of applied roasting temperature it is more favorable to change it from 150 °C to 135 °C, than the other way round. Changing the relative humidity of roasting air from 5 to 0.3%, lower degradation of tocopherols in CB occurs when the process is conducted at 150 °C. It may be further concluded that a direct dependence between the velocity of roasting air varied during the process and the concentration of tocopherols in extracted CB may not be indicated. In conclusion, it is stated that the temperature of the air applied during the roasting process has the decisive influence on the tocopherol content in CBs extracted from cocoa beans subjected to the process.     

Quality of Malaysian cocoa butter during storage

Malaysian pure prime pressed and deodorised cocoa butters were obtained from local cocoa grinders and analysed for quality deterioration. Approximately 5 kg of each sample was packed in corrugated paper boxes lined with low‐density polyethylene plastic material of thickness 73.2 µm. The water vapour transmission rate and gas transmission rate (for oxygen) of the plastic material were 3.21 g m^?2 day^?1 (37.8 °C, 90 ± 2% RH) and 71.57 cm³ m^?2 day^?1 (23.0 °C, 0% RH) respectively. The butters were stored at 15 ± 4 °C and 70 ± 4% RH for up to 24 months. Samples were taken every 2 months and analysed for free fatty acid content, saponification value, iodine value, refractive index and peroxide value. The findings indicated that the free fatty acid content, iodine value and peroxide value of both types of cocoa butter increased with storage duration. The other parameters showed no significant changes. However, the free fatty acid content and peroxide value after 24 months of storage were still below the limits specified in Malaysia. Therefore we conclude that both types of Malaysian cocoa butter are still in good condition after 24 months of storage, with minimal quality deterioration. Copyright © 2004 Society of Chemical Industry     

Effect of autoclaving cocoa nibs before roasting on the precursors of the Maillard reaction and pyrazines

Nibs of raw cocoa (N) were roasted (R) at 150 °C for 38 min. Some samples were autoclaved at 121 °C for 15 min (A) and roasted (AR) at 150 °C for 38 min. The samples were then analysed for moisture content, water activity (a_w), reducing sugar and amino group (α-N) levels and, absorption at 275 nm (A₂₇₅) for a trichloro acetic acid (TCA) extract and at 280 nm (A₂₈₀) for the distillate. Tri- and tetramethylpyrazines were quantified by solid phase micro extraction-gas chromatography (SPME-GC). There was a reduction in the levels of α-N, in the order N > A > R > AR. The same sequence was observed for reducing sugars. The tetramethylpyrazine had an Area_pyrazine/Area_{internal standard} of N < R < A < AR and for trimethylpyrazine the order was N < A < R < AR. After autoclaving, the A_tetra/A_tri decreased from 31.30 (N) to 11.06 (A). With roasting, this ratio was 2.18 (R) and 2.58 (AR). Autoclaving nibs before roasting significantly influenced the levels of compounds which contribute to cocoa flavour formation and increased the concentration of tri- and tetramethylpyrazines in the headspace of cocoa samples. Autoclaving prior to roasting also affected the sensory properties of the samples.     

Tocopherol content,peroxide value and sensory attributes in roasted peanuts during storage

The objective of this study was to determine changes in tocopherol content, peroxide value (PV) and sensory attributes from roasted peanuts during storage at 40 °C. There were no differences in tocopherol contents between roasted and raw peanuts except in α‐tocopherol content that decreased after roasting. All tocopherol contents decreased during storage. On the contrary, lipid oxidation indicators such as PV and the intensity ratings of oxidised and cardboard flavour increased during storage. On the other hand, the intensity ratings of roasted peanutty flavour decreased with storage time. Good correlations were observed between tocopherol contents and PVs. Tocopherol contents could be used as indicator of oxidative state in peanut products.     

Investigation of aromatic compounds in roasted cocoa powder

Most of the volatile compounds identified are highly significant in determining cocoa powder flavour, and this paper demonstrates that basic sensory perceptions (undesirable, bitter pungent, repulsive, fruity, nutty, floral, vegetal, and sweet chocolate) can be totally explained by aroma compounds with R²-adjusted values of 0.85 and greater. Samples from five geographical origins of cocoa bean were characterized by chemical compounds and sensory attributes. The aroma extracts were obtained by a two-step procedure involving (1) preliminary steam distillation under reduced pressure to evaluate the methylpyrazines generated in roasted cocoa powder by spectrophotometry (flavour index), and (2) Likens-Nickersons simultaneous steam distillation and solvent extraction method with added NaCl. The distilled compounds were separated by adsorption chromatography in six fractions depending on the polarity. A combined total of 114 compounds were detected by gas chromatography/mass spectrometry, 110 of which were identified. About 15 components in the mean milligrams per kilogram range (1.09–4.67 mg kg^–1) and 95 components in the mean micrograms per kilogram range (12–980 µg kg^–1) were quantified. The major components of cocoa aroma were 2,3,5,6-tetramethylpyrazine, benzaldehyde, 2-phenylacetaldehyde, acetophenone, 3-methylbutyric acid, 5-methyl-2-phenyl-2-hexenal, ethyl phenylacetate, and 3-hydroxy-2-methyl-4-pyrone (mean greater than 1.30 mg kg^–1).     

Extraction and determination of methylpyrazines in cocoa beans using coupled steam distillation-microdistillator

The formation of methylpyrazines was determined in fermented cocoa beans (Ivory Coast), in laboratory and industrially roasted samples. The determination of these methylpyrazines was studied by coupled steam distillation-microdistillation as the extraction method and gas chromatography using capillary column and a thermionic detector. The monomethyl-; 2,3-dimethyl-; 2,5-dimethyl-; 2,6-dimethyl-; trimethyl- and the tetramethylpyrazine were detected in non-roasted cocoa beans. Their concentration increased rapidly in laboratory roasted cocoa beans and industrial samples, only the tetramethylpyrazine showed a maximum peak of concentration. The principal compound was the tetramethylpyrazine in fermented and roasted cocoa beans. The determination of the different methylpyrazines in cocoa beans would permit both the evaluation of cocoa mass quality and the control of the cocoa roasting process.     

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.     

Factors influencing quality variation in cocoa (Theobroma cacao) bean flavour profile — A review

This review examined the factors that influence flavour volatiles of cocoa beans and the volume of work that needs to be done on these factors and their impact on the flavour volatiles of commercial cocoa beans. Cocoa bean flavour is one of the most important quality attributes as flavour is central to acceptability of cocoa beans and cocoa products such as chocolate. The complex composition of cocoa bean flavour depends on bean genotype, postharvest treatments such as pulp pre-conditioning, fermentation and drying, industrial processes such as roasting as well as the type of soil and age of cocoa tree. The bean genotype determines the chemical composition of the bean, specifically the contents of bean storage proteins, polysaccharides, and polyphenols. This determines the quantities and type of precursors formed during fermentation and drying processes leading to flavour formation, hence, influencing both flavour type and intensity. Cocoa bean fermentation and drying result in the breakdown of the storage proteins by endogenous proteases into amino acids and short chain oligopeptides while the polysaccharides are also degraded by invertase to glucose and fructose. The amino acids, oligopeptides, glucose and fructose react with each other during the roasting process to produce the typical cocoa flavour volatiles. Polyphenols are also oxidized by polyphenol oxidase during fermentation and drying which reduce the astringency and bitterness of the beans, thus, enhancing the flavour of cocoa beans. However, the extent to which other factors such as age of the cocoa tree and soil chemical compositions influence the formation of flavour precursors and their relationships with final flavour quality remains unclear. With increasing demand for sustainable production of high quality cocoa beans, greater understanding of factors contributing to the variations in flavour character would have significant commercial implications.     

Evaluation of high oleic-high stearic sunflower hard stearins for cocoa butter equivalent formulation

Cocoa butter equivalents (CBEs) are produced from vegetable fats by blending palm mid fraction (PMF) and tropical butters coming from shea, mango kernel or kokum fat. In this regard, high oleic-high stearic (HOHS) sunflower hard stearins from solvent fractionation can be used in CBE production since their compositions and physical properties are similar to those found in the above-mentioned tropical butters. In this work, three sunflower hard stearins (SHS) ranging from 65% to 95% of disaturated triacylglycerols and a shea stearin (used as reference) were blended with PMF to evaluate their potential use in CBEs formulation. Isosolid phase diagrams of mixtures of PMF/SHS showed eutectic formation for SHS 65 and SHS 80, but monotectic behaviour with softening effect for SHS 95. Three CBEs from SHS and shea stearin were formulated according to phase behaviour diagrams and solid fat content data at 25 °C. Isosolid phase diagrams of mixtures of these CBEs with cocoa butter showed no eutectic behaviour. Therefore, CBEs elaborated from SHS exhibited full compatibility with cocoa butter.     

Pod storage time and spontaneous fermentation treatments and their impact on the generation of cocoa flavour precursor compounds

Most of volatile flavour compounds occurred during the cocoa postharvest operations including pod storage and fermentation whom effects on these metabolites were aimed by the present study. Three different spontaneous fermentation treatments were performed on the farm, and the main isolated yeasts were identified using PCR-DGGE technique. Fermented cocoa beans were solar-dried, and their flavour compounds were identified using solid phase microextraction technique–gas chromatography–mass spectrometry. The main results showed that Pichia kudriavzevii was common yeast involved in the cocoa fermentation. Thirty flavour precursor compounds grouped into six chemical families including alcohols and pyrazines were identified in raw cocoa samples. ACP showed that short durations of pod storage and fermentation promote the formation of flavour precursors of cocoa. No spontaneous cocoa fermentation treatment influenced the occurrence of aroma compounds. The generation of flavour compounds depends only on the pod storage and the fermentative microorganisms of cocoa.     

Evaluation of purine alkaloids and diketopiperazines contents in processed cocoa powder

 This paper describes the evaluation of purine alkaloids and diketopiperazines (DKPs) contents in 24 samples of processed non-alkalinized cocoa powder. The chemical data obtained were related to sensory evaluation and subjected to analysis of variance. During cocoa roasting, the content of DKPs can be increased, resulting in a negative influence on the sensorial quality of cocoa. A pronounced bitter metallic taste can originate from some of these compounds, and becomes stronger when these DKPs are combined with purine alkaloids. The cocoa roasting process at different temperatures (125, 130, 135, 140 and 145  °C) and durations (3, 10, 16 and 20 min) was evaluated by measuring the flavour indices, formol numbers and DKP contents in 24 samples of cocoa powder. The addition of reducing sugars was also evaluated in the same industrial processes in 27 other samples of cocoa powder. The higher the roasting temperature of the cocoa was, the more elevated the flavour index became, except at temperatures up to 140  °C, where DKPs were generated in large proportions. Received: 2 February 1999 / Revised version: 23 April 1999     

Synthesis and Aroma Properties of New Alkyloxazoles and Alkylthiazoles Identified in Cocoa Butter from Roasted Cocoa Beans

Previous work provided evidence for the occurrence of new alkyloxazoles and alkylthiazoles in the volatiles of cocoa butter from roasted cocoa beans. The synthesis, mass spectral data and sensory properties of these compounds are reported.     

Physicochemical traits and sensory quality of commercial butter produced in the Azores

In the volcanic islands of the Azores archipelago, pasture is available the entire year and affects the composition of bovine milk fat. The composition of cows' milk butter manufactured in this region was evaluated. All brands showed excellent microbiological and oxidative quality. The fatty acid profile range presented a low n-6/n-3 ratio (1.81–3.38), low atherogenic (2.86–3.11) and thrombogenicity (3.27–3.60) indices and reduced cholesterol content (136–143 mg 100 g⁻¹). In addition, Azorean butters have a high content of conjugated linoleic acid (0.44–0.64 mg 100 g⁻¹), β-carotene (0.12–0.17 mg 100 g⁻¹) and α-tocopherol (1.40–2.20 mg 100 g⁻¹). Sensory analysis revealed high scores for appearance, consistency and flavour of all brands. These results indicate that Azorean butters produced from cows’ milk based on grass-feeding have a potentially healthier fat content and a desirable flavour that, associated with its “natural image”, may be promoted for product differentiation.     

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