Actas do 5º Encontro de Química de Alimentos
Qualidade, Segurança
& Inovação
U n i v e r s i d a d e C a t ó l i c a P o r t u g u e s a E s c o l a S u p e r i o r d e B i o t e c n o l o g i a S o c i e d a d e P o r t u g u e s a d e Q u í m i c a P O R T O , M A I O 2 0 0 1Actas do 5º Encontro de Química de Alimentos
Qualidade, Segurança
& Inovação
Universidade Católica Portuguesa Escola Superior de Biotecnologia Sociedade Portuguesa de Química
APOIOS: Programa Operacional Ciência, Tecnologia, Inovação (Quadro Comunitário de Apoio III) FCT (Fundação para a Ciência e Tecnologia), no âmbito do Programa FACC (Fundo de Apoio à Comunidade Científica)
Ficha Técnica
Livro de Actas do 5º Encontro de Química de Alimentos
Editores: Prof. F. Xavier Malcata Prof. F. Javier Carballo
ISBN: 972-98476-2-2
Coordenação e Revisão: Manuela Pascoal
Design e Composição Gráfica: Kai Sprecher - Serviços de Edição da ESB/UCP Impressão: Orgal Impressores
Depósito Legal: 000 000 000 000 000 000 Tiragem: 500 exemplares
Esta publicação reúne as comunicações apresentadas no 5º Encontro de Química de Alimentos, sob a forma de Conferências, Comunicações Orais e em Painel.
A aceitação das comunicações foi feita com base nos resumos apresentados; o texto integral que aqui se apresenta é da inteira responsabilidade dos respectivos autores.
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Summary
Thermal degradation of sucrose produces, among others, hydroxymethylfurfural, a colouring and flavouring compound, that can be further degraded into 5-methylfur-fural and 2- 5-methylfur-furaldheyde (fur5-methylfur-fural). The research reported in this paper is concerned with the content in these compounds of the syrups traditionally used in Portuguese pastry. The method used to quantify these compounds is HPLC with diode array detection. Results indicate the presence of hydroxymethylfurfural and furfural in the syrups produced at 168 and 180°C.
Introduction
The traditional Portuguese pastry is very rich and diversified. There is, however, an “ingredient” that is common to many formulations: sugar boils. These sugar boils are made of a mixture of 3 parts of sugar (sucrose) and 1 part of water, that is heated in an open pan to relatively high temperatures. There are thirteen different syrups, which only differ in the heating temperature and, when this temperature is high enough, in the final water content (Table 1). Very little is known about these widely used syrups.
The goal of this research is to characterise the composition of the traditional sugar boils, used in the pastry industry, and later use this information to develop new “sugar free” formulations to substitute these boils.
Thermal degradation of sucrose has been studied by several authors [2,3,4]. Sucrose is degraded into fructose and glucose and at high temperatures breakdown products, such as hydroxymethylfurfural (HMF), are formed, causing coloration and character-istic caramel flavour[1]. The reaction, which initiates the thermal degradation of the monosaccharides, fructose and sucrose, is the enolisation, known as the Bruijn van Eckenstein rearrangement. When the temperature is high enough, HMF can be fur-ther degraded into products such as 5-methylfurfural and 2-furaldheyde (furfural)[5].
Characterization of traditional degrees of sugar boiling:
hydroxymethylfurfural (hmf), 5-methylfurfural and 2-furaldheyde
Quintas M. and Silva C. L. M
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Previous research carried out in our group [6] indicated that sucrose degraded only in the syrups prepared at 168 and 180°C. These boils presented also colour and dis-tinctive aroma formation. The study presented in this paper was conducted to inves-tigate the content in HMF, 5-methylfurfural and furfural (using HPLC) in syrups that presented sucrose degradation.
Methods
Samples of sugar syrups were prepared, following traditional recipes, and were injec-ted in a Beckman System Gold with a Waters Spherisorb®S5 ODS2 column, using a acetonitrile/water (60:40) mobile phase running at 1.2 ml/min. The peaks were detected using a diode array detector and analysed at a wavelength of 284 nm [7]. Standard solutions of hydroxymethylfurfural, 5-methylfurfural and 2-furaldheyde were prepared and analysed.
Results and Discussion
Within the experimental conditions, the separation of HMF, furfural and 5-methylfur-fural was achieved and the retention times identified were 2.22, 3.33 and 4.10 mi-nutes, respectively. The results from the HPLC analysis of the samples show the pre-sence of HMF (peak at 2.22 min) and furfural (peak at 3.33 min) in the traditional syrups prepared at 168 and 180°C.
Table 1
The Traditional Degrees of Sugar Boiling (from Lees & Jackson [1])
Name Traditional Test * Observation * Approx.Temp. (°C)
Thread (gloss) A Thin strands 103
Large Thread (Large gloss) A Stronger and more strands 104
Small Pearl B Forms small droplets 105
Large Pearl B Forms large droplets 106
Blow (soufflé) C Bubbles set on syrup 110
Feather B Forms feathery hard strands 111
Small Ball B Syrup forms soft ball 116
Large Ball B Syrup forms hard ball 120
Light Crack B Forms thin sheet 129
Medium Crack B Sheet forms, slightly brittle 133
Hard Crack B Rapidly formed sheet 143
Extra Hard Crack B Sheet shows signs of browning 168
Caramel B Brown brittle sheet forms 180
* traditional test used before the general availability of thermometers:
A - Place sample, of cooked syrup, between two wetted fingers and open; B - Dip finger or spatula in water, then in portion of boil, return to cold water; C - Blow on spatula dipped in syrup
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The chromatograms did not revealed a peak at 4.10 min, indicating the absence of 5-methylfurfural in the samples.
The concentrations of HMF and furfural determined in the samples are presented in Table 2.
References
[1] LEES, R., JACKSON, E.B., 1975, Sugar Confectionery and Chocolate Manufacture,
Chemical Publishing, New York
[2] PONCINI, L., 1980, Thermal Degradation of Sucrose in Solution – A Review, The Int. Sugar J., 332-335
[3] MANLEY-HARRIS, M., RICHARDS, G.N., 1996, Di-D-Fructose Dianhydrides and
Related Oligomers from Thermal Treatments of Inulin and Sucrose,
Carbohydrate Research, 287, 183-202
[4] DEFAYE, J., GARCÍAFERNANDEZ, J.M., 1995, The Oligosaccharide Components of
Caramel, Zuckerindustrie, 120 (8), 700-704
[5] KROH, L.W., 1994, Caramelisation in Food and Beverages, Food Chem., 51,
373-379
[6] QUINTAS, M., SILVA, M.F.B., SILVA, C.L.M, 2001, Characterization of Traditional
Degrees of Sugar Boiling: Sucrose Degradation and Water Content –
pre-sented as a poster in III Congresso Ibero Americano de Ingeniería dos Alimentos, March 2001, Valencia, Spain.
[7] HO, P., HOGG, T. A., SILVA, M.C.M., 1999, Application of a Liquid
Chromatographic Method for the Determination of Phenolic Compounds and Furans in Fortified Wines, Food Chem., 64, 115-122
Acknowledgements
Authors would like to acknowledge Ligia Lobo and Luis Ribeiro for their precious help for the experimental work.
Author M. Quintas would like to thank Praxis XXI Ph.D. grant BD/20057/99 to Fundação para a Ciência e Tecnologia – Ministério da Ciência e Tecnologia.
Table 2 Concentrations of HMF and furfural determined in the sugar boils prepared at 168 and 180°C
Temp. (ºC) CHMF (g/g) Cfurfural (g/g)
168 7.78E-05 4.28E-06
