Influence of roasting conditions on fatty acid composition and oxidative changes of cocoa butter extracted from cocoa bean of Forastero variety cultivated in Togo

Cocoa butter is responsible for physico-chemical, rheological and sensory properties of chocolates. Forastero cocoa beans are rich in cocoa butter. Roasting of cocoa beans is an essential step of their processing, giving rise to many desirable transformations. On the other hand, it causes changes in certain valuable ingredients including also cocoa butter. This article studies the influence of roasting conditions, i.e. temperature, humidity and flow velocity of roasting air, on the fatty acid composition, peroxide value and content of conjugated dienes and trienes in cocoa butter extracted from cocoa beans. Generally, in most cases roasting did not increase the peroxide value. In the constant conditions due to obtained results of PV, CD and CT values it is recommended to roast cocoa beans at the temperature of 150 °C, 1 m/s air velocity and 5% relative humidity. In the variable conditions lower values of PV, CD and CT were achieved when cocoa beans were roasted in variants with changing temperature from 150 °C to 135 °C or with changing air velocity from 1 to 0.5 m/s. Generally, the roasting process substantially did not change the content of each fatty acid, regardless of the applied conditions.     

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.     

Effect of the roasting process on glass transition and phase transition of Colombian Arabic coffee beans

This paper presents results of the analysis of organic coffee beans cultivated in Departamento del Cauca - Colombia. Beans studied are of the Coffea Arabica species cultivated in mountain soils of altitude close to 1500 m. Samples from green and roasted beans were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and X-ray diffractometry (XRD). We intend to relate the features of the heating spectra with the transformation experimented by the coffee. Glass transition and phase transitions were examined. DSC and TGA spectra show that the green coffee experiments a high and fast decomposition after 200 ^°C until 289 ^°C with a remarkable transformation in a close range around 210 ^°C. XRD shows significant changes for green and roasted beans associated to the amount of caffeine hydrates and caffeine anhydrous. Fit of XRD curves by Lorentzian shows a considerable increase of the active crystalline phase at 2θ equal to 20.4⁰ for the roasted coffee. The results obtained from this study contribute to the insight associated with the final quality of coffee dependent on roasting methods. Better quality of coffee requires a refined and very controlled roasting process around of 218 ^°C with a slow thermal treatment since the room temperature until the 200 ^°C.     

Effect of moisture on salmonella spp. heat resistance in cocoa and hazelnut shells

The heat resistance of food-poisoning outbreak and non-outbreak associated strains of Salmonella (S. Enteritidis, S. Montevideo, S. Napoli, S. Oranienburg, S. Poona, S. Senftenberg and S. Typhimurium) was established in confectionery-related materials such as crushed cocoa bean and hazelnut shells at low moisture contents (≤ 4% w/w). The two most heat resistant strains in cocoa and hazelnut shells at ca. 4% w/w moisture were S. Oranienburg and S. Enteritidis PT30. Both strains were associated with outbreaks from dried materials. Their D_100°C values were ca. 2.5 min in crushed cocoa bean shells and 7–11 min in crushed hazelnut shells. Addition of moisture to ca. 7% w/w markedly reduced D-values (D_80°C of 2–4.5 min) for both strains in the two matrices.     

Antioxidant capacity of cocoa beans and chocolate assessed by FTIR

The total antioxidant capacity (TAC) and total phenolic compounds (TPC) of cocoa beans and chocolate produced from spontaneous and inoculated fermentations of different cocoa varieties were evaluated. Fourier transform infrared spectroscopy (FTIR), as well as conventional methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), was used to determine TAC and TPC. Chocolate showed higher (p < 0.05) TPC (47.17–57.16 mg GAE/g) and TAC (1.66–2.33 mM TE/g and 8.86–11.35 mM TE/g as measured by DPPH and ABTS, respectively) than cocoa beans (6.30–26.05 mg GAE/g, 0.24–1.17 mM TE/g and 1.29–4.83 mM TE/g for TPC, DPPH and ABTS, respectively). Partial least square (PLS) model for infrared data showed a good calibration coefficient (R²cal > 0.94), indicating that the FTIR technique represents a fast and reliable tool to evaluate TPC and TAC in cocoa beans and chocolate.     

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.     

Feasibility study on the use of Fourier transform near-infrared spectroscopy together with chemometrics to discriminate and quantify adulteration in cocoa beans

Fourier transform near-infrared (FT-NIR) spectroscopy combined with Support Vector Machine (SVM) and synergy interval partial least square (Si-PLS) was attempted in this study for cocoa bean authentication. SVM was used to develop an identification model to discriminate between fermented cocoa beans (FC), unfermented cocoa beans (UFC) and adulterated cocoa bean (5–40 wt/wt.% content of UFC). Si-PLS model was used to quantify the addition of UFC in FC. SVM model accurately discriminated the cocoa bean samples used. After cross-validation, the optimal identification rate was 100% in both the training set and prediction set at three principal components. For quantitative analysis, Si-PLS model was evaluated according to root mean square error of prediction (RMSEP) and coefficient of correlation in prediction (R_pred). The results revealed that Si-PLS model in this work was promising. The optimal performance of Si-PLS model showed an excellent predictive potential, RMSEP = 1.68 and R_pred = 0.98 in the prediction set. The overall results indicated that FT-NIR spectroscopy together with an appropriate multivariate algorithm could be employed for rapid identification of fermented and unfermented cocoa beans as well as the quantification of UFC down to 5% in FC for quality control management.     

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.     

Antioxidant and biological activity of phenolic pigments from Theobroma cacao hulls extracted with supercritical CO2

Theobroma cacao L. (Sterculiaceae) and cocoa-derived products are phenolics-rich food; these products are largely studied because of the antioxidant and antiradical in vitro properties of phenolic constituents. Cocoa hulls are the principal by-product of cocoa, separated from the cotyledons during the pre-roasting process or after the roasting process of T. cacao beans (de-hulling/de-husking step). This by-product is a matrix rich in fiber (namely insoluble, but also represented by pectins) and phenolics. Supercritical CO₂ is a powerful mild technology able to extract and fractionate from plant or animal foods without the use of organic solvent. This approach was used to extract some phenolics fractions from cocoa hulls. Only two recovered fractions, (150 bar, 50 °C, re-dissolved in acetone; 200 bar, 50 °C, re-dissolved in acetone), apparently free from (-)epicatechin, catechin and phenolic acids, showed protective action in an in vitro test (SH-SY5Y cells, differentiated to a neuronal phenotype using retinoic acid and then exposed to ischemic damage), similar to the action of cabergoline and vitamin E. We suggest the use of supercritical CO₂ for the isolation of bioactive fractions from cocoa hulls and an in vitro model as a useful model to study the antioxidant/antiradical properties of isolated phenolic pigments.     

Optimization of deacidification of low-calorie cocoa butter by molecular distillation

Molecular distillation for deacidification of crude low-calorie cocoa butter was optimized. Processing parameters of molecular distillation including evaporator temperature, feed flow rate and pressure were investigated on the quality indicators (acid value and color) of refined low-calorie cocoa butter by single factor experiments. Optimum operating parameters were obtained by response surface methodology. Evaporator temperature, feed flow rate and their interaction term showed significant effects on the responses (deacidification rate and Lovibond color), but pressure was not significant. The optimum parameters for production of low-calorie cocoa butter with low acidity and light color were as follows: evaporator temperature 185.0 °C, feed flow rate 2.3 mL/min and pressure of 1.0 Pa. The predicted results of deacidification rate and yellow and red values (95.25%, 5.5 and 0.7) were close to the experimental values (95.48 ± 0.48%, 5.5 ± 0.7 and 0.6 ± 0.1).     

Antioxidant properties of polyphenol-rich cocoa products industrially processed

Fermentation and roasting are the main causes of polyphenol degradation during the process for obtaining cocoa products. In the present study, a process for obtaining polyphenol-rich cocoa products on an industrial scale is described. The process avoids the fermentation and roasting steps and includes a step for the inactivation of the enzyme Polyphenol Oxidase (PPO), which helps preserve the polyphenol content present in the raw cocoa bean. In addition, our study evaluates the antioxidant capacity and characterizes the flavonoid profile of the polyphenol-rich cocoa products obtained from the natural polyphenol-rich cocoa cake. Using different protocols, we have obtained three cocoa extracts with high polyphenol content, namely extracts A (167 mg/g), B (374 mg/g) and C (787 mg/g). The scavenging capacity of the extracts was measured as their ability to bleach the stable radicals DPPH and ABTS⁺ while their antioxidant effect was evaluated with the FRAP assay. The results for A, B and C in the DPPH test expressed as Trolox equivalent (μmol)/mg dry weight of extract were 0.2, 1.4 and 3.0, respectively; in the ABTS test the results were 1.0, 4.7 and 9.8. The antioxidant capacity expressed as ascorbic acid equivalent (μmol)/mg dry weight of each product were 17.2, 76.1 and 207.7, respectively. The scavenging properties of cocoa powder against the superoxide anion, H₂O₂, HClO, and peroxynitrite were also determined. The IC₅₀ (μg/mL) values in the hypoxanthine/xanthine oxidase test were 77.5, 12.3 and 10.3, for A, B and C, respectively, while as an HOCl scavenger the IC₅₀ (μg/mL) values were 225.4, 73.2 and 21.5. As a peroxynitrite anion scavenger, only extract C had a relevant effect, with IC₅₀ (μg/mL) values of 76.1 or 110.0 in the absence or presence of bicarbonate. None of the extracts tested showed activity in the hydrogen peroxide test, but B and C significantly increased the deoxyribose degradation in the absence of ascorbate. Likewise, none of the extracts inhibited the ferrous or copper chelating activity at 100 μg/mL, but they inhibited the lipid peroxidation in brain homogenates and human plasma through non-enzymatic generation systems, with extract C giving the best IC₅₀ (μg/mL) values: 17.4 and 8.1 against lipid peroxidation in brain homogenates and human plasma, respectively. In conclusion, if the extractive protocol is well characterized, defined and optimized, cocoa could constitute a source of polyphenols for enriching foods, nutraceuticals and alimentary supplements.     

Development of an ultrasonic shear reflection technique to monitor the crystallization of cocoa butter

The quasi-isothermal crystallization process of cocoa butter was monitored by an ultrasonic shear reflection technique utilizing a custom-built experimental set-up in a temperature controlled environment. To facilitate the interpretation of the measurement results, the propagation of shear waves was first theoretically studied in different configurations of gas, liquid or solid layers with varying thickness for the case of normal incidence, yielding theoretical equations of the shear wave reflection coefficient (swRC) for different layering conditions. The typical experimentally observed pattern of the swRC during quasi-isothermal cocoa butter crystallization was subsequently linked to the theoretical equations. The remarkable oscillatory damped response in the swRC as function of the crystallization time could be explained by constructive and destructive interference of a first reflection at the boundary between a plexiglass delay line and the crystallized cocoa butter and a second reflection occurring at the interface between crystallized and liquid substance. This hypothesis was supported by the excitation frequency dependence of the oscillations. The quality of the fit of the theoretical model to the experimental results was very good and also the reproducibility between different independent measurements was acceptable. Finally, measurements at different temperatures (18 °C and 20 °C) suggested that the technique was able to detect differences in crystallization behavior, as measurements at 18 °C displayed faster oscillations compared to measurements at 20 °C. Moreover, this was also confirmed by the theoretical model, as a higher value of the crystallization rate parameter K, exhibited more rapid oscillations.     

Determination of 5-hydroxymethyl-2-furfural and 2-furfural in oils as indicators of heat pre-treatment

This study describes a method for the determination of 5-hydroxymethyl-2-furfural (HMF) and 2-furfural (F) in oils. The method entails liquid–liquid extraction and reversed-phase liquid chromatography. Spiked hazelnut oil was used to test the accuracy and reliability of the method. Furan compounds were extracted from oil using 70% methanol. Mean recoveries were 97 ± 2% and 99 ± 1% for HMF and F, respectively. To investigate the presence of HMF and F in oils, seven oily nuts and seeds were roasted at 180 °C for 30 min. Different oils were found to contain HMF and F ranging from 0.8 to 13.8 and 1.4 to 8.7 mg/kg, respectively. Increasing solvent polarity also increased the rate of HMF transferred to the oil. Spectral analyses of the 70% methanol extracts indicated that absorbance at 285 nm may be used to monitor the accumulation of furan compounds in oil phase during the roasting process of nuts.     

The cooling rate effect on the microstructure and rheological properties of blends of cocoa butter with vegetable oils

The elasticity (G′) and yield stress (σ¹) of blends of cocoa butter (CB) in vegetable oils (i.e., 30% CB/canola and 30% CB/soybean oil) crystallized at temperatures (T_Cr) between 9.5 °C and 13.5 °C and two cooling rates (1 °C/min and 5 °C/min) were determined, evaluating their relationship with parameters associated with the formation and structural organization of the crystal network [i.e., solid fat content (SFC), Avrami index, crystallization rate, fractal dimension (D)]. The results showed that T_Cr and cooling rate had a different effect for each blend on the three-dimensional organization of the crystal network, and on the proportion and size of β′ and β crystals. Thus, under low supercooling conditions at both cooling rates, the crystallized CB/canola oil blend was formed by a mixture of small β′ and large β crystals that provided high G′ and σ¹ at low SFC (i.e., 20.5–20.9%) and D (i.e., 1.66–1.72) values. The CB/soybean oil blend achieved similar G′ and σ¹ independent of cooling rate only at high supercooling. In this case, the crystal network was formed mainly by small β′ crystals with SFC (i.e., 25.4–26.3%) and D (i.e., 2.86–2.79) values higher (P < 0.05) than in the CB/canola oil blend at low supercooling.     

Quantification of 3-aminopropionamide in cocoa, coffee and cereal products

Based on recent results confirming 3-aminopropionamide (3-APA) as a very effective precursor of acrylamide in the absence of further “catalysts”, this compound was quantified for the first time in cocoa masses, cocoa beans, coffee and cereal products by LC–MS–MS after derivatisation with dansyl chloride. Cocoa masses contained >3000 μg/kg of 3-APA, but varied significantly in its concentration. For the quantification of acrylamide (AA) in cocoa and coffee, an improved isolation procedure using charcoal was developed. In various samples of unroasted and roasted cocoa beans, the concentrations of AA were by a factor of >5 lower than those of 3-APA, but the concentrations of 3-APA and AA were more closely correlated as compared to the concentrations of AA and Asparagine. Experiments on authentic cocoa beans from Ghana and Sulawesi indicated that the thermal generation of 3-APA during roasting was much more pronounced as compared to its biochemical formation. By administering fermented cocoa beans with [¹³C₄ ¹⁵N₂]-asparagine before roasting, 3-APA was confirmed as transient intermediate in AA formation during cocoa roasting. Among the cereal products analysed, in particular popcorn contained quite high amounts of 3-APA, which were also well correlated with the AA concentration. Contrary, in coffee products, 3-APA was always lower than AA.     

Profiles of volatile compounds and sensory characteristics of Robusta coffee beans roasted by hot air and superheated steam

Although superheated steam (SHS) roasting has proved to be capable of improving selected quality of roasted Robusta coffee beans, impact of SHS roasting on aroma characteristics of the beans is not well understood. This study therefore aimed to investigate the effect of SHS roasting on aroma profiles and sensory characteristics of Robusta beans undergone SHS roasting at 190–250 °C; results were compared with those of beans roasted by hot air (HA). Sensory characteristics of selected samples were also compared with HA-roasted Arabica beans. Forty five aroma compounds were identified; most were fully developed in beans roasted at 230 °C and tended to degrade in beans roasted at 250 °C. SHS roasting led to more extensive formation of aroma compounds contributing to caramel note, while helped reduce formation of major contributors to spicy, roasty and burnt notes. SHS-roasted Robusta beans exhibited more resemblance to Arabica beans than their HA-roasted counterpart.     

The production of aldehydes from amino acids in roasted cocoa

It has been suggested in the literature that aldehydes are produced from the amino acids in roasting cocoa beans by the Strecker degradation. [U-¹⁴C]-L-Leucine [U-¹⁴C]-L-3-phenylalanine and [U-¹⁴C]-L-threonine-were used in an investigation to confirm this mechanism. The labelled amino acids were introduced into ripe cocoa beans which were then fermented, dried and roasted under conditions approaching those of normal practice. The carbonyl compounds were collected as 2,4-dinitrophenylhydrazones and identified by thin-layer chromatography (t.l.c.) and autoradiography. The major products from [¹⁴C]-L-leucine and [¹⁴C]-L-3-phenylalanine were isovaleraldehyde and phenylacetaldehyde respectively, which are the aldehydes expected from a Strecker degradation. Some condensation products and other radioactive carbonyl compounds were also noted. The degradation of threonine appeared to occur early in the roasting process and to be more complex. Acetaldehyde was identified and it is suggested that this was produced via the Strecker aldehyde.     

Changes on the levels of serotonin precursors – tryptophan and 5-hydroxytryptophan – during roasting of Arabica and Robusta coffee

The levels of free and total tryptophan and of 5-hydroxytryptophan (5-HTP) were investigated in green and roasted grains and beverages of Coffea arabica L. (Arabica) and Coffea canephora Pierre var. robusta (Robusta). Grains were light, medium and dark roasted. Free and protein tryptophan were extracted before and after hydrolysis. The levels of tryptophan and 5-HTP were quantified simultaneously by ion-pair HPLC and fluorimetric detection after derivatisation with o-phthalaldehyde. Robusta green coffee had higher total and protein tryptophan, whereas Arabica had higher free tryptophan levels. 5-HTP was not detected in the samples before and after roasting. Free tryptophan was completely degraded during roasting. Roasting significantly affected protein tryptophan. The rate of loss was smaller in Arabica compared to Robusta at every roasting degree. A beverage prepared the Brazilian way with a medium-roasted coffee provided 1.4–2.5 mg tryptophan/50 ml cup.     

Clovamide and phenolics from cocoa beans (Theobroma cacao L.) inhibit lipid peroxidation in liposomal systems

Neo-synthesized clovamide and a phenolic cocoa extract (fermented cocoa from Ghana) were evaluated for their capacity to inhibit lipid peroxidation. Their effect was first investigated on phospholipid organic solutions, and then on liposomal systems prepared by high pressure homogenization process. Antioxidants were added to liposomal system following two different protocols (before and after the homogenization treatment) and their protective action was evaluated monitoring the oxidative status of liposomes (exposed to light at room temperature or heated at 40 °C) over three weeks. The results confirmed a significant protective effect of clovamide on liposomal model systems and, in a minor extent, also of cocoa extract. The capacity of phosphatidylcholine liposomes to incorporate clovamide was also evaluated; it was shown that more than 50% of clovamide was englobed in liposomes, although the addition of clovamide solution before the homogenization process led to the isomerization of the molecule from trans to cis form.     

Anti-inflammatory effect of aqueous extracts of roasted and green Coffea arabica L.

Green coffee contains a large quantity and variety of polyphenols and flavonoids. The roasting affects the composition of the polyphenols in coffee, due to the formation of compounds generated by Maillard reaction, which can have anti-inflammatory or antioxidant potential. The anti-inflammatory and antioxidant effects of aqueous extracts of green (AGCa) and roasted (ARCa) coffee beans were investigated in animal models and using a DPPH radical scavenging test. In the formalin test the extracts reduced licking activity only in the late phase. The inhibitory values of oedema at 3 h post-carrageenan were 53% and 74% for 100 and 300 mg/kg of the AGCa extract and 36% for ARCa (300 mg/kg). Leukocyte recruitment into the peritoneal cavity was inhibited by the extracts. The antioxidant activities of the extracts were higher than the reference antioxidants, ascorbic acid and butylated hydroxytoluene. These results indicate that coffee extracts exhibit anti-inflammatory and antioxidant properties.