The Kinetics of Total Phenolic Content and Monomeric Flavan-3-ols during the Roasting Process of Criollo Cocoa

Cocoa beans are the main raw material for the manufacture of chocolate and are currently gaining great importance due to their antioxidant potential attributed to the total phenolic content (TPC) and the monomeric flavan-3-ols (epicatechin and catechin). The objective of this study was to determine the degradation kinetics parameters of TPC, epicatechin, and catechin during the roasting process of Criollo cocoa for 10, 20, 30, 40, and 50 min at 90, 110, 130, 150, 170, 190, and 200 °C. The results showed a lower degradation of TPC (10.98 ± 6.04%) and epicatechin (8.05 ± 3.01%) at 130 °C and 10 min of roasting, while a total degradation of epicatechin and a 92.29 ± 0.06% degradation of TPC was obtained at 200 °C and 50 min. Reaction rate constant (k) and activation energy (Ea) were 0.02–0.10 min−1 and 24.03 J/mol for TPC and 0.02–0.13 min−1 and 22.51 J/mol for epicatechin, respectively. Degradation kinetics of TPC and epicatechin showed first-order reactions, while the catechin showed patterns of formation and degradation.

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abstract: During cocoa beans roasting, there are physicochemical changes that develop the chocolate quality attributes. Roasting systems have a particular influence on the development of these characteristics, and the effects of operation variables for each system must be evaluated. The objective of this study was to evaluate the effect of roasting time and temperature in a rotatory system on cocoa beans physicochemical parameters of quality as moisture, water activity, pH, total acidity, color , total phenolic content (TPC), and DPPH radical capacity. Cocoa beans were roasted as a function with a central rotatable design with 22 + 5 central points and 4 axial points ( 1.414, 1, 0, +1, and +1,414) and a response surface methodology was applied. Temperature and time levels were 110–170°C and 5–65 minutes, respectively. The effect of the variables was nonlinear and modeled with a second-order response polynomial. Roasting time and temperature presented a significative effect ( ) on the response variables except for both TPC and DPPH radical capacity in aqueous extract.

title: (-)-Epicatechin mediates beneficial effects of flavanol-rich cocoa on vascular function in humans.
abstract: Epidemiological and medical anthropological investigations suggest that flavanol-rich foods exert cardiovascular health benefits. Endothelial dysfunction, a prognostically relevant key event in atherosclerosis, is characterized by a decreased bioactivity of nitric oxide (NO) and impaired flow-mediated vasodilation (FMD). We show in healthy male adults that the ingestion of flavanol-rich cocoa was associated with acute elevations in levels of circulating NO species, an enhanced FMD response of conduit arteries, and an augmented microcirculation. In addition, the concentrations and the chemical profiles of circulating flavanol metabolites were determined, and multivariate regression analyses identified (-)-epicatechin and its metabolite, epicatechin-7-O-glucuronide, as independent predictors of the vascular effects after flavanol-rich cocoa ingestion. A mixture of flavanols/metabolites, resembling the profile and concentration of circulating flavanol compounds in plasma after cocoa ingestion, induced a relaxation in preconstricted rabbit aortic rings ex vivo, thus mimicking acetylcholine-induced relaxations. Ex vivo flavanol-induced relaxation, as well as the in vivo increases in FMD, were abolished by inhibition of NO synthase. Oral administration of chemically pure (-)-epicatechin to humans closely emulated acute vascular effects of flavanol-rich cocoa. Finally, the concept that a chronic intake of high-flavanol diets is associated with prolonged, augmented NO synthesis is supported by data that indicate a correlation between the chronic consumption of a cocoa flavanol-rich diet and the augmented urinary excretion of NO metabolites. Collectively, our data demonstrate that the human ingestion of the flavanol (-)-epicatechin is, at least in part, causally linked to the reported vascular effects observed after the consumption of flavanol-rich cocoa.

title: Impact of fermentation, drying, roasting and Dutch processing on flavan-3-ol stereochemistry in cacao beans and cocoa ingredients
abstract: This paper reports a systematic study of the level of flavan-3-ol monomers during typical processing steps as cacao beans are dried, fermented and roasted and the results of Dutch-processing. Methods have been used that resolve the stereoisomers of epicatechin and catechin. In beans harvested from unripe and ripe cacao pods, we find only (-)-epicatechin and (+)-catechin with (-)-epicatechin being by far the predominant isomer. When beans are fermented there is a large loss of both (-)-epicatechin and (+)-catechin, but also the formation of (-)-catechin. We hypothesize that the heat of fermentation may, in part, be responsible for the formation of this enantiomer. When beans are progressively roasted at conditions described as low, medium and high roast conditions, there is a progressive loss of (-)-epicatechin and (+)-catechin and an increase in (-)-catechin with the higher roast levels. When natural and Dutch-processed cacao powders are analyzed, there is progressive loss of both (-)-epicatechin and (+)-catechin with lesser losses of (-)-catechin. We thus observe that in even lightly Dutch-processed powder, the level of (-)-catechin exceeds the level of (-)-epicatechin. The results indicate that much of the increase in the level of (-)-catechin observed during various processing steps may be the result of heat-related epimerization from (-)-epicatechin. These results are discussed with reference to the reported preferred order of absorption of (-)-epicatechin > (+)-catechin > (-)-catechin. These results are also discussed with respect to the balance that must be struck between the beneficial impact of fermentation and roasting on chocolate flavor and the healthful benefits of chocolate and cocoa powder that result in part from the flavan-3-ol monomers.

title: Thermal stability of catechin and epicatechin upon disaccharides addition
abstract: Influence of sucrose and trehalose addition on epimerisation and thermal degradation of catechin and epicatechin have been studied. Sucrose addition accelerated epimerisation of catechin and epicatechin at 80 and 100 °C. Addition of trehalose had protective effect on epimerisation of catechin and epicatechin. Considering thermal degradation, it was confirmed that thermal degradation of catechin and epicatechin follows the first-order kinetics. Increasing the temperature causes shorter half-lives of catechin and epicatechin. Addition of sucrose had negative effect on catechin stability. However, in samples with epicatechin, sucrose impact was temperature dependent. Trehalose addition had positive impact on preventing catechin and epicatechin degradation almost doubling the half-life of studied compounds. Data presented in this study could help to predict chemical conversions of investigated phenolics in various food systems and to prolong their shelf life in thermally processed foods.

title: Assessment of flavanol stereoisomers and caffeine and theobromine content in commercial chocolates.
abstract: Assessment of the flavanol composition of 41 commercial chocolates was by HPLC-DAD. Among individual flavonols ranged from 0.095 to 3.264mgg(-1), epicatechin was the predominant flavanol accounting for 32.9%. Contrary to catechin, epicatechin was a reliable predictive value of the polyphenol content. Conversely the percentage of theobromine used as a proxy measure for nonfat cocoa solids (NFCS) was not a good predictor of epicatechin or flavanol content. In a further chiral analysis, the naturally occurring forms of cocoa flavanols, (-)-epicatechin and (+)-catechin, was determined joint the occurrence of (+)-epicatechin and (-)-catechin due to the epimerization reactions produced in chocolate manufacture. (-)-Epicatechin, the most bioactive compound and predominant form accounted of 93%. However, no positive correlation was found with% cocoa solids, the most significant quality parameter.

title: Physicochemical properties and antioxidant capacity of raw, roasted and puffed cacao beans.
abstract: The antioxidant capacity and attributable bioactive compounds of puffed cacao beans were investigated. Roasting was carried out at 190°C for 15min and puffing was performed at 4-7kgf/cm(2). Cacao beans puffed at 4kgf/cm(2) showed the highest total polyphenols (23.16mgGAE/gsample) and total flavonoids (10.65mgCE/gsample) (p<0.05). As the puffing pressure increased, the amount of total polyphenols and total flavonoids decreased. The antioxidant capacity of cacao beans reflected the total polyphenols and flavonoids measured. The quantities of theobromine, catechin, epicatechin, and procyanidin B2 were higher in cacao beans puffed at 4kgf/cm(2) than in roasted cacao beans. Puffed cacao beans received a good sensory score in flavor, but sourness increased as puffing pressure increased. Thus, these results suggest that, in cacao bean processing, puffing could be an alternative to roasting, which provide a rich taste and high antioxidant capacity.

title: Biological activities of (-)-epicatechin and (-)-epicatechin-containing foods: Focus on cardiovascular and neuropsychological health.
abstract: Recent studies have suggested that certain (-)-epicatechin-containing foods have a blood pressure-lowering capacity. The mechanisms underlying (-)-epicatechin action may help prevent oxidative damage and endothelial dysfunction, which have both been associated with hypertension and certain brain disorders. Moreover, (-)-epicatechin has been shown to modify metabolic profile, blood's rheological properties, and to cross the blood-brain barrier. Thus, (-)-epicatechin causes multiple actions that may provide unique synergy beneficial for cardiovascular and neuropsychological health. This review summarises the current knowledge on the biological actions of (-)-epicatechin, related to cardiovascular and brain functions, which may play a remarkable role in human health and longevity.

title: Changes in the flavan-3-ols, anthocyanins, and flavanols composition of cocoa beans of different Theobroma cacao L. groups affected by roasting conditions
abstract: In the present study, the effect of roasting conditions on the individual flavan-3-ols, anthocyanins, and flavanols content of cocoa beans of five different Theobroma cacao L. groups was studied. The raw cocoa beans were roasted at four different temperatures (110, 120, 135, and 150 °C) and three different relative air humidities (0.3, 2.0, and 5.0 %). The great variations in the contents of both total and individual phenolic compounds among the different studied cocoa groups were observed. In general, the cocoa beans of the Forastero group from Brazil exhibited the highest content of individual flavan-3-ols, anthocyanins, and flavanols, while the samples of the Trinitario type from Papua New Guinea had the lowest polyphenols levels. Roasting significantly affected the profile and levels of the flavan-3-ols, anthocyanins, and flavanols in cocoa beans. The changes depended upon the different cocoa types evaluated and their processing conditions. A decrease in epicatechin, procyanidin B, procyanidin C1, both anthocyanins, and quercetin glycosides was observed in all of the five cocoa groups tested after roasting. This reduction coincided with the increase in catechin and quercetin contents in roasted cocoa beans from the five cocoa groups.

title: Flavanols, proanthocyanidins and antioxidant activity changes during cocoa (Theobroma cacao L.) roasting as affected by temperature and time of processing.
abstract: The effect of roasting on the content of flavanols and proanthocyanidins and on the antioxidant activity of cocoa beans was investigated. Cocoa beans were roasted at three temperatures (125, 135 and 145 °C), for different times, to reach moisture contents of about 2 g 100 g(-1). Flavanols and proanthocyanidins were determined, and the antioxidant activity was tested by total phenolic index (TPI), ferric reducing antioxidant power (FRAP) and total radical trapping antioxidant parameter (TRAP) methods. The rates of flavanol and total proanthocyanidin loss increased with roasting temperatures. Moisture content of the roasted beans being equal, high temperature-short time processes minimised proanthocyanidins loss. Moisture content being equal, the average roasting temperature (135 °C) determined the highest TPI and FRAP values and the highest temperature (145 °C) determined the lowest TPI values. Moisture content being equal, low temperature-long time roasting processes maximised the chain-breaking activity, as determined by the TRAP method.

title: The kinetics of polyphenol degradation during the drying of Malaysian cocoa beans
abstract: The main objective of the study was to determine the kinetics of the polyphenol oxidation reaction in cocoa beans during air drying at various air temperatures and humidities. The temperatures used were between 40 and 60 °C and the relative humidities were between 50 and 80%. The higher the temperature and relative humidity of the drying air, the lower the amount of polyphenol residue in the cocoa beans, because of enzymatic oxidation of polyphenols. At higher drying temperatures, non-enzymatic oxidation of polyphenols could also occur. Computer simulation results gave rate constants for the polyphenol oxidation reaction (k 1 ) and the condensation reaction (k 2 ), at various air conditions, in the range of 0.055-0.200 and 0.136-0.155 h -1 respectively. The activation energies obtained for the polyphenol oxidation reaction were in the range of 27 800-30 312 J K -1 mol -1 . The reaction kinetics of the enzymatic browning reaction fitted a pseudo first-order reaction.

title: The Drying Kinetics and Polyphenol Degradation of Cocoa Beans
abstract: This study investigated the kinetics of drying and polyphenol degradation during hot air and sun drying of cocoa beans. Hot air drying was carried out using a constant humidity-controlled (50% relative humidity) oven at temperature range of 60–80C, and sun drying was carried out by exposing the beans under direct sunlight. Several semi-theoretical models were used to model the kinetics of moisture diffusion and it was found that the Page and Logarithmic models were able to provide good prediction. A first-order reaction kinetics was used to predict the polyphenol degradation process with rate constants ranging from 0.011/h to 0.052/h. Activation energy for polyphenol degradation was determined at 8.97 kJ/mol using the Arrhenius equation. Effective diffusivity during drying was found within the order of magnitude (10−12–10−10 m2/s) reported in most drying literatures. 
 
Practical Applications 
The understanding of moisture diffusion is important in dryer design especially in the determination of effective diffusivities during drying. Polyphenols are important antioxidants that are beneficial to human health. By investigating the polyphenol degradation kinetics, this helps to link the reactions with moisture diffusion kinetics.

title: Kinetic modeling of phenolic compound degradation during drum-drying of apple peel by-products
abstract: The apple peel, a by-product of apple processing, has a high total phenolic content (TPC); however, these compounds can be highly thermosensitive and unstable. Therefore, the aim of this study was to determine the degradation kinetics of the TPC in apple peels during drum-drying as a stabilization and recovery method.  were dried at 110, 120, 130 or 140 °C for 250 s with a constant drum clearance (0.2 mm). TPC degradation exhibited first-order kinetics and their retentions at the end of the process were 73.13% at 110 °C, 57.28% at 120 °C, 43.40% at 130 °C and 21.10% at 140 °C. Finally, empirical models were significantly fitted to predict the TPC as the apple peels reached a certain level of dehydration, which may be useful from the processing standpoint and validate the use of drum-drying as a process tool for the recovery of apple industrial wastes.

title: Kinetics of hot air roasting of cocoa nibs and product quality
abstract: Cocoa beans are widely used in the manufacturing of various food and beverage products such as chocolates, powdered drink, cookies, confectioneries, and others. Processing plays a vital role in governing the final flavor profile of cocoa beans especially during roasting. The current studies aimed to determine the transport properties of cocoa nibs during roasting and also to investigate the quality of roasted cocoa nibs. Cocoa nibs were roasted at temperatures of 120, 130, and 140 °C inside a hot air convective oven. Kinetics analyses showed that overall rates of sensible heating (from T = 27 to 100 °C) were in the range of 5.1–9.5 °C/min as compared to overall rates of effective roasting (from T = 100 °C onwards) in the range of 0.9–1.4 °C/min. The observed moisture content profiles followed the typical exponential decay as commonly explained by the Fick's second law of diffusion. The dependency of thermal and moisture diffusivities with temperatures could be described using quadratic and Arrhenius models, respectively. It was determined that the average order of magnitude for moisture diffusivity was 10−10 m2/s as compared to 10−9 m2/s for thermal diffusivity. High roasting temperature had a negative impact on cocoa polyphenols where greater degradation was observed. Sensory evaluation showed that cocoa liquor produced from the higher temperature treatment (T = 140 °C) had the highest cocoa flavor. 
 
Practical applications 
Information on the roasting kinetics and moisture/thermal diffusivities are important design parameters for cocoa roaster. Changes in flavor quality during roasting are important in governing the development of flavor in the finished chocolate products. Therefore, the current studies contribute knowledge to the cocoa industry for both equipment and chocolate manufacturers.

title: Effect of thermal treatment on phenolic compounds from plum (prunus domestica) extracts – A kinetic study
abstract: The effect of thermal treatment on the degradation of the polyphenolic compounds in plum extract was investigated in the range of 70–110 °C by means of fluorescence spectroscopy and spectrophotometric techniques. The fluorescence results suggested that plum extract represents a multicomponent system with different fluorescence species. The heating of plum extract resulted in structural changes that led to a significant decrease in fluorescence intensity at higher temperature when the solutions were excited at 300 nm, whereas, when excited at 410 nm, significant increase in fluorescence intensity was measured in the temperature range of 70 and 110 °C. Degradation rate constants were estimated using a first order kinetic model. Temperature dependence of the degradation rate constants were expressed according to the Arrhenius model. The total monomeric anthocyanins showed the highest degradation in comparison to other polyphenols, as well as to antioxidant activity.

title: Kinetic and thermodynamic compensation. A current and practical review for foods.
abstract: Kinetic and thermodynamic compensations have been reported in many chemical, physical, biological and food processes. Kinetic compensation can be found for any process and when it takes place, it gives information about the reaction mechanism and whether the reaction is controlled by enthalpy or entropy. It consists of the linear relationship between the logarithm of the frequency factor (lnk0) and the activation energy (Ea), both previously obtained from the Arrhenius equation for different values of an environmental variable (e.g. pH, concentration of any substance not involved in the process, pressure, water activity, etc.). A mathematical consequence of kinetic compensation is the isokinetic temperature, this being the temperature at which the kinetic constant should be the same regardless of the environmental variable. Thermodynamic compensation can be found for any process involving an equilibrium and consists of the linear relationship between the variation of enthalpy and entropy, both previously obtained from the Van't Hoff equation for different values of an environmental variable. A mathematical consequence of thermodynamic compensation is the isoequilibrium temperature, this being the temperature at which the equilibrium constant should be the same regardless of the environmental variable. According to the transition state theory, some kinetic constants can be related to the equilibrium constant of the initial equilibrium stage between the reagents and the transition state. For these cases, it can be concluded that both compensations are related mathematically and therefore not only does the existence of one kind of compensation imply the existence of the other, but the isokinetic and isoequilibrium temperatures should both be the same, or at least very close to each other. However, there is no reason that forces the linearities that cause either kind of compensation. So, some processes have shown these linear relationships while others have not. Moreover, some authors have reported that, due to the fact that the estimates of the parameters for the couples lnk0-Ea and ΔH≠-ΔS≠ being correlated with each other, there is a statistic compensation that consists of the propagation of experimental errors, and this effect has to be considered before concluding kinetic and/or thermodynamic compensations. This work reviews how to deal with kinetic and thermodynamic compensations physically, mathematically and statistically, prior to a second part that reviews the food processes for which one or both of these compensations have been studied.

title: Thermal stability of phytochemicals, HMF and antioxidant activity in cape gooseberry (Physalis peruviana L.)
abstract: Cape gooseberry is a fruit recognised for having relevant contents of health-promoting compounds. Changes in the content of phytochemicals (ascorbic acid, β-carotene, catechin and epicatechin), hydroxymethylfurfural (HMF) and antioxidant activity of this fruit were studied at various temperatures and times. Ascorbic acid degradation was described by a first order reaction. β-carotene was not degraded and followed an isomerization reaction from 80 °C onwards. Formation of HMF was described with a consecutive zero together with a first order reaction model. The contents of catechin and epicatechin increased at 40 °C. More than three competing reactions did not allow to make kinetic modelling. Antioxidant activity followed fractional first order conversion model. Comparison with kinetics found in other fruits showed that health-promoting compounds of cape gooseberry are relatively more stable to heat treatment. This makes cape gooseberry suitable for the preparation of foods (jam, juices and dehydrated fruit) with relevant health-promoting compounds contents.