Chem Eng.

ISSN 1392 – 1231. CHEMINĖ TECHNOLOGIJA. 2009. Nr. 3 (52)

5-Hydroxy-2-methylfurfural and acrylamide formation in heat-treated foods such as whole-grain bread in Latvia
N. Bobere, I. Jakobsone, J. Kviesis, A. Podjava
University of Latvia, Chemistry Department, Food Chemistry Centre, Kr. Valdemara str. 48, LV-1013 Riga, Latvia E-mail: nataliabobere@mail.ru Received 15 June 2009; Accepted 2September 2009
5-Hydroxy-2-methylfurfural (HMF) and acrylamide (AA) are two potential mutagenic and carcinogenic substances detected in cereal products such as carbohydrate-rich baked whole grain bread. During baking, complex chemical processes such as the Maillard reaction and caramelisation take place, leading to HMF formation. Both reactions involve reducing sugars generated from starch andsucrose hydrolysis during baking. In addition, amino acids like asparagine and glutamine are important precursors of AA in the Maillard reaction. Ten samples of whole-grain rye and/or wheat flour bread obtained from the local market were analysed by high performance liquid chromatography with UV detection (HPLC-UV) and liquid chromatography – tandem mass spectrometry (LC–MS/MS) for HMF and AA,respectively. Both methods are known to be most useful, and their sensitivity is similar to that of gas chromatography (GC) or GC–MS for the quantitative determination of these substances. As a result of these studies, HMF was determined in the range from 2.5 ±0.3 to 412.2 ±1.8 mg/kg. The results obtained for AA showed a range of content from 4.31 ±0.18 to 35.6 ±1.1 mg/kg; however, the concentrations of AAin five samples were beyond the LC–MS/MS method linearity and can be presented as < 2.5 mg/kg (four samples) and > 50 mg/kg (one sample).

Introduction
Nowadays, it is clear that the main route for acrylamide (AA) and 5-hydroxy-2-methylfurfural (HMF) formation is the Maillard reaction [1, 2]. This reaction is associated with flavour and colour characteristics of heated foods like bread.Toxicological studies with HMF have been performed since early 90s [3, 4], however, studies of AA as a potentially carcinogenic food contaminant appeared in April 2002. HMF and AA can be considered as quality indicators of fried or baked food. Factors such as temperature, heat intensity and water activity, used in the processing technologies, affect the final concentrations of these substances in theproduct. In case of whole-grain bread, a significant influence on HMF and AA exposures is exerted by environmental conditions (climate, soil), post-harvest treatment, duration and conditions of storage [5]. Studies of HMF and AA in foodstuffs have attracted interest because they exhibit mutagenic and DNA strandbreaking activity. Moreover, AA has been classified as ”potentially carcinogenic tohumans” by the International Agency for Research on Cancer (IARC) on the basis of sufficient evidence for its carcinogenicity in experimental animals [4]. Various methods for the quantitative analysis of these substances can be applied. The most often used are based on HPLC and GC–MS (for HMF), LC–MS, GC–MS and LC–MS/MS (for AA). New methods have been mentioned recently [6–9]. It is mentioned in theliterature that exposure to these toxic substances can be lowered by avoiding starchy foods. However, it is not recommended to decrease the intake of healthy grain products, such as whole-grain bread [10]. The advantage of whole-grain bread is a high content of fibre which bind

carcinogenic substances and toxins and thus reduce the level of these compounds in human body. Whole-grain bread is alsorich in essential amino acids, vitamins B and mineral substances. Unfortunately, in the literature there are no reports on the quantities of HMF and AA in Latvian baked products. For this reason, we report here our first results in this field.

Experimental
REAGENTS AND MATERIALS. HMF (≥ 95% purity) and acrylamide (≥ 98% purity) were purchased from Fluka. Methanol and acetonitrile (both with...