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 (aw), 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 Areapyrazine/Areainternal standard of N < R < A < AR and for trimethylpyrazine the order was N < A < R < AR. After autoclaving, the Atetra/Atri 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.

Um procedimento de Microextração em Fase Sólida em Headspace (HS-SPME) para isolamento e determinação de alquilpirazinas em liquor de cacau, usando Cromatografia Gasosa com Detecção por Ionização em Chama (GC-FID) é apresentado aqui. As condições operacionais de HS-SPME foram otimizadas usando extrações de amostras fortificadas com quantidades conhecidas de alquilpirazinas tipicamente encontradas em derivados de cacau. A eficiência máxima de extração foi obtida com fibras de SPME recobertas com 65 µm de Carbowax/divinilbenzeno. Em adição, os melhores resultados foram obtidos usando 60 ºC como temperatura de extração, 15 min como tempo de equilíbrio amostra/headspace e 45 min como tempo de extração. Observou-se também que o uso de solução aquosa saturada de NaCl para suspender as amostras durante as extrações resultou em um incremento significativo nas áreas dos picos. Este procedimento se mostrou efetivo para a determinação das razões pirazínicas (quocientes entre as áreas dos picos de alquilpirazinas), que são úteis como parâmetros de qualidade para liquor de cacau.A Headspace Solid Phase Microextraction (HS-SPME) procedure for isolation and determination of alkylpyrazines in cocoa liquor, using Gas Chromatography with Flame Ionization Detection (GC-FID) 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.Keywords: cocoa liquor, alkylpyrazines, aroma, Maillard reaction products, SPME IntroductionThe processing of cocoa seeds (Theobroma cacao, L.) 1 comprises their drying, fermentation of sugars contained in the pulp covering the seeds, roasting, separation and grounding of the roasted nibs. The resulting fatty solid product (known as cocoa liquor) is the base raw material for chocolate industry. The most significant flavor-impact substances on cocoa derivatives are N-and O-containing heterocyclic compounds generated during the roasting, which are products of the complex sequence of heatinduced chemical processes collectively known as Maillard reactions. 2 The substrates for the Maillard reactions are reducing sugars, small peptides, aminoacids and / or triglycerides contained in the raw, unroasted material. For cocoa, in terms of contribution to their sensorial characteristics (and, in consequence, to their commercial value), the most im...

Cocoa mass was treated with glucose and/or glycine before roasting. For glucose-treated samples the reductions in reducing sugars and free amino acids were 41.1 and 56.9% respectively, whereas for glycine-treated samples the respective reductions were 16.2 and 37.4%. The combination of glucose plus glycine treatment led to 39.0 and 48.9% reductions in reducing sugars and free amino acids respectively. For free amino acids the reductions in control and glucose-treated samples were similar, 56.2 and 56.9% respectively, indicating that the added glucose did not signi®cantly (P < 0.05) in¯uence the free amino acid uptake. When glycine was added, the consumption of free amino acids (37.4%) was lower than for the control and glucose treatments. When glucose and glycine were added, the reduction in free amino acids (48.9%) was lower than for the control and glucose treatments but higher than for the glycine treatment. Apparently, glycine addition inhibited the reducing sugar and free amino acid consumption, whereas glucose addition enhanced the reducing sugar and free amino acid consumption. The glucose plus glycine treatment was similar to the glycine treatment in the contents of 2,5-dimethyl-and trimethylpyrazines. For 2-methylpyrazine the value for glucose-treated samples was lower than for control and glycine-treated samples but almost equal to the value for the glucose plus glycine treatment. It is concluded that the addition of glucose and/or glycine does not affect pyrazine production.

literature. The two models were used for the simultaneous extraction and enrichment of organochlorinated pesticides from aqueous matrixes to an organic solution appropriate for the gas chromatographic analysis of the pesticide. It was established that the performance of one of the modified micro-extractors permits the pre-concentration of the pesticides to a level that allow their quantitation at the trace level with electron capture detection. It is thus concluded that the glass micro-extractor is a suitable tool for the sample preparation step in the gas chromatographic analysis of environmental pollutants of the class of pesticides.Keywords: pre-concentration of aqueous samples; organochlorinated pesticide; GC analysis. NOTA TÉCNICA INTRODUÇÃOA análise de pesticidas organoclorados em água é comumente realizada por CGAR-DCE (Cromatografia Gasosa de Alta Resolução com Detecção por Captura de Elétrons) porque, aliando-se a capacidade de resolução cromatográfica da CGAR, com a seletividade e sensibilidade do DCE para organoclorados, é possível processar amostras complexas e viabilizar as monitorações destes compostos em níveis de concentrações tão baixas como 0,1 µgL -1 , que é a máxima permitida para cada pesticida, segundo a União Européia 1,2 . Embora existam menções de que estas análises sejam realizadas por injeção cromatográfica direta da água contaminada, a alternativa mais divulgada é a de pré-processamento da matriz aquosa, para gerar uma amostra analítica apropriada para a análi-se por CGAR-DCE. Isto é decorrente das dificuldades analíticas impostas pelas amostras aquosas, que geralmente são altamente complexas, incompatíveis com os sistemas CGAR-DCE e contêm os poluentes em altos graus de diluição 3,4 . A pré-concentração de compostos agroquímicos de matrizes aquosas pode ser realizada por métodos de extração líquido-líquido 5,6 e de extração em fase sólida 7,8 . No caso dos pesticidas organoclorados, é viável a extração com destilação por arraste com vapor d'água 4 , com a qual é possível conseguirem-se eficiências de extração superiores às realizadas por headspace e processos de stripping com gás 9 . Para extração com arraste por vapor d'água e pré-concentração de pesticidas de amostras aquosas, Verzele e colaboradores 9 desenvolveram um microextrator de vidro (Figura 1C), no qual pode-se operar com 1 ml de solvente orgânico, para extrações de 50 ml, ou mais, da fase aquosa. No microextrator a destilação ocorre simultaneamente com processos de extração líquido-líquido, lí-quido-vapor e vapor-vapor, entre a fase aquosa e a fase orgânica. O enriquecimento da fase orgânica decorre da proporção volumétrica favorável entre o solvente e a fase aquosa. Resultados analíticos obtidos com o microextrator, tanto na forma original 10 , quanto após modificações 11 ,indicaram potencialidades desta metodologia de extração e pré-concentração em uma única etapa, que motivaram os estudos aqui relatados, de exploração deste dispositivo para análises de pesticidas organoclorados em águas. Foram construídos e testados do...

No abstract