Nelson Horacio Pezoa Garcia

Structural and chemical changes in cocoa (Theobroma cacao L) during fermentation, drying and roasting

Cocoa seeds and pulp were fermented for 144 h, followed by natural drying. The tegument was removed and the cotyledons were broken into nibs which were roasted at 150 °C for 30 min. Non-fermented material, material fermented for 24, 48 and 72 h, material fermented for 144 h and then dried, and also the roasted nibs, were all prepared for chemical and microscopic analyses. Light microscopy revealed the presence of anionic and cationic residues and of neutral sugars. During fermentation there was a reduction in the cytoplasmic content of phenolic compounds and in the number of protein bodies. The cell wall showed a reduction in anionic residues and a loss of crystallinity. These alterations were maximum after 72 h. Drying and roasting increased the number of damaged cells and reduced the amount of cytoplasmic material. The chemical analyses generally confirmed the microscopy results. The concentration of amino-terminal groups and total free amino acids increased during fermentation (up to 72 h), but returned to the initial values after roasting. The principal chemical changes were related to reducing sugars, free amino acids, proteins and phenols, and PCA was suggested as a useful tool to compare different samples. Microscopic analysis revealed the degradation of protein and phenolic bodies and cellular damage during roasting. © 2000 Society of Chemical Industry

Effect of polyphenol oxidase (PPO) and air treatments on total phenol and tannin content of cocoa nibs

O sabor do cacau e fortemente influenciado pelos polifenois. Esses compostos sofrem uma serie de transformacoes durante o processamento do cacau dando origem ao sabor caracteristico do cacau. O uso de polifenol oxidase (PPO) exogena mostrou ser util na reducao do teor de polifenois em nibs de cacau. O efeito de uma PPO associada ou nao com ar sobre o teor de fenois totais e taninos foi avaliado. Nibs de cacau foram autoclavados e tratados com PPO ou agua na presenca ou nao de um fluxo de ar por 0,5; 1; 2 e 3 horas. O teor de fenois totais foi reduzido nos tratamentos com PPO ou agua, mas quando associados com ar houve um aumento desses teores. O teor de taninos foi reduzido apenas pelo tratamento com agua e ar.

A Headspace Solid Phase Microextraction (HS-SPME) method for the chromatographic determination of alkylpyrazines in cocoa samples

A Headspace Solid Phase Microextraction (HS-SPME) procedure for isolation and determination of alkylpyrazines in cocoa liquor, using Gas Chromatography with Flame Ionization Detection (GCFID) for the separation and detection of the analytes, is presented here. The HS-SPME operational conditions were optimized using extractions of samples spiked with known amounts of alkylpyrazines typically found on cocoa products. The maximum extraction efficiency was obtained using SPME fibers coated with 65 µm Carbowax/divinylbenzene. Additionally, the best results were achieved with extraction temperature of 60 oC, 15 min of sample/headspace equilibration time and 45 min extraction time. It was also observed that suspending the samples in saturated aqueous NaCl solution during extractions resulted in a significant increment on the peak areas. This procedure was found to be effective to determine the so-called pyrazinic ratios (quotient between peak areas of alkylpyrazines), which are useful as quality parameters for cocoa liquor.

Use of a proteolytic enzyme in cocoa (Theobroma cacao L.) processing

ABSTRACT Protein hydrolysis using an exogenous protease on cocoa nibs was performed to verify the formation of precursors and the effect on cocoa flavour. An experimental design was used to check the influence of temperature (30 to 70 o C) and enzyme : substrate ratio [E/S] (97.5 to 1267.5 U g -1 of protein). The % Degree of Hydrolysis (% DH) was affected mainly by [E/S] leading to a 4-fold increase (from 5 to 20 %) after 6 hours of treatment. During cocoa nibs roasting, there was a greater consumption of hydrolysis compounds in the sample treated with protease as compared to the control, indicating their participation in the Maillard reaction. An increased perception of chocolate flavour and bitter taste was observed in a product formulated with protease treated cocoa. Key words: Cocoa, flavour, protein hydrolysis, processing ∗ Author for correspondence INTRODUCTION Fermented and dried cocoa beans constitute the raw material used by the chocolate industry to produce various different products, which are largely appreciated for their characteristic flavour. During fermentation the pulp surrounding the seeds is metabolized by the microorganisms resulting in a temperature rise and a drop in pH, which are responsible for cotyledon death. During this some other substances such as ethanol, acetic and lactic acids and the formation of flavour precursors, basically peptides, free amino acids and reducing sugars (Reinnecius et al., 1972; Mohr et al., 1976) are also produced. These precursors participate in the Maillard reaction during cocoa roasting, leading to the characteristic chocolate flavour. Proteolysis is very important for cocoa flavour development (Voigt et al., 1994a; 1994b). Amino acids and peptides are produced during fermentation by the combined action of an aspartic endoprotease and a carboxipeptidase. The main substrate for these enzymes is a globulin described as a cocoa vicilin. A specific cocoa aroma was obtained when this globulin was degraded by exogenous proteases and the resulting products were roasted in the presence of reducing sugars (Voigt et al., 1994a; 1994b). However, other cocoa proteins should be considered in flavour precursor formation (Lerceteau et al., 1999). During subsequent roasting, amino acid levels were reduced, but this reduction was not complete and there were different rates of reaction for the distinct amino acid groups (Seiki, 1973; Abeygunasekera and Jansz, 1989).

OBTENÇÃO E UTILIZAÇÃO DA ENZIMA POLIFENOLOXIDASE EXTRAÍDA DE POLPA DE PINHA (Annona squamosa L.) MADURA NO MELHORAMENTO DO SABOR DO CACAU (Theobroma cacao L.)

The present work had as aim to study the obtaining and the uses of polyphenoloxidase enzyme (PPO) extracted from ripe custard apple pulp on the reduction of polyphenolic compounds with decrease adstringency and bitterness of cocoa nuts processed at nibs form. The PPO was extracted with 0.025M potassium phosphate buffer (pH 7.5), adding ammonium sulfate to the enzyme precipitation. The powdered material obtained was called partially purified enzyme, being the analyses of activity carried out with catechol as substract, showing biochemical characteristics of 5.0 to 6.5 stability pH and 10 to 30°C stability temperature the nibs were autoclaved (121°C for 15 minutes) and non-autoclaved from the same origin, raw nuts insuficiently fermented and dried were soaked in a solution of the enzyme containing 200 units/min/mL, for 30, 60, 90, 210 and 360 minutes, at 23°C and pH 6.0 . The nibs were homogeneized with the enzyme solution each 15 minutes, dried, ground and became unfatted. After enzymatic treatment over 210 minutes carried out on the non-autoclaved unfatted cocoa nibs, it was possible to observe diminishing of 15% in the total phenol, 15% tannin content, 10% of flavan-3-ois and 18% of anthocyanidins concentrations. The nibs of autoclaved unfatted cacao showed diminishing of 25% in the total phenol, 26% of tannins 23% of flavan-3-ois, and 51% of anthocyanidins concentrations.

Proteínas da semente de cupuaçu e alterações devidas à fermentação e à torração

Cupuacu (Theobroma grandiflorum Schum) is a native fruit from northern Brazil with great economic potential. Its productive chain is currently sustained by the pulp market. The seed, treated as a by-product of the pulp industrialization, presents considerably protein content. However, very little or nothing is known on its eletrophoretic profile and amino acids, the main protein fractions and alterations due to the fermentation and toasting. The objective of this study was to characterize protein changes in cupuacu seeds, fermented beans, and roasted beans, through the analysis of the electrophoresis profiles, aminograms, and protein fractionations based on solubility. Fermentation and roasting promoted a slight reduction in the total protein and amino acid contents. The seeds and fermented beans presented four main protein bands with 15.5, 20.4, 27.1, and 33.6 kDa. The beans submitted to fermentation followed by roasting presented only one strong protein band with an apparent molecular weight of 21.0 kDa. The extractions for protein fractionation based on solubility did not result in pure protein fractions. Four main bands were observed in all isolated protein fractions. The 21.1 kDa band was predominant in all cases. This band is apparently very similar to the albumin fraction of cocoa, whose apparent molecular weight is 21.3 kDa.

Fragmentação mecânica de amêndoas de cupuaçu (Theobroma grandiflorum)

Cupuassu (theobroma grandiflorum) is a native fruit from the Brazilian Amazon region whose seeds suitably fermented, dried and roasted can be used to manufacture a product similar to chocolate. This work aimed at devising an alternative way of cracking the dried but not roasted kernels by using a roller crusher, followed by using a set of sieves for separating the fractions. The variables studied for determining the nibs (scrapped cotyledons) acquisition yield as well the purity of such material (expressed as percent of shell and embryo fragments) were the moisture of the whole kernel and the differential speed of the double rollers of the crusher. The results confirmed that the moisture of the whole kernel was the variable that most influenced the cracking of kernels. The greater yield obtainment of nibs was reached at the 5% moisture level of the whole kernels. The variation of the double rollers differential speed did not present any significant difference as regards the nibs acquisition yield. As to the percent values of shell and embryo fragments, no studied variables have shown any significant difference on such a response values, even so the results were very well satisfactory, presenting values below the 1.75%. The yield of this alternative process is 90% of the cotyledons acquisition from certain kernels mass. As a conclusion, the process proposed herewith set oneself up as a mechanized alternative, showing good nibs acquirement yield, and percent of shells and embryo below the tolerated value.