Comparing sugar components of cereal and pseudocereal flour by GC–MS analysis

Highlights

• It is possible to compare types of plants against the content of mono- and disaccharides.

• GC-MS and correlation analysis has been used.

• There are great opportunities for carrying out similar testing in the food industry.

Abstract

Gas chromatography with mass spectrometry was used for carrying out a qualitative analysis of the ethanol soluble flour extract of different types of cereals bread wheat and spelt and pseudocereals (amaranth and buckwheat). TMSI (trimethylsilylimidazole) was used as a reagent for the derivatisation of carbohydrates into trimethylsilyl ethers. All samples were first defatted with hexane. (In our earlier investigations, hexane extracts were used for the analysis of fatty acid of lipid components.)

Many components of pentoses, hexoses and disaccharides were identified using 73 and 217 Da mass and the Wiley Online Library search. The aim of this paper is not to identify and find new components, but to compare sugar components of tested samples of flour of cereals bread wheat and spelt and pseudocereals (amarnath and buckwheat). Results were analysed using descriptive statistics (dendrograms and PCA). The results show that this method can be used for making a distinction among different types of flour.

Introduction

Wheat is one of the most important grain crops in the world. Its flour is used for making various food products such as bread, noodle and cakes (Gao et al., 2010). On the other hand, different studies have verified that spelt is suitable for the preparation of common cereal products such as bread, flakes for breakfast and pasta (Pelillo, Ferioli, Iafelice, Marconi & Caboni, 2010). Authentic spelt flour is much more expensive for production than wheat flour, and the use of spelt has long been confined to the animal feeding (Ruibal-Mendieta et al., 2005). Buckwheat is not a cereal but is usually grouped with cereals due to its ways of cultivation and utilisation (Kim, Kim & Park, 2004). Rediscovery, promotion, and dramatic re-introduction of amaranth began in the mid 1970s and continued to grow strongly to the present day (Marcone, 2000). The nutrient composition of wheat, spelt, amaranth and buckwheat have been examined by many researchers (Alvarez-Jubete, Arendt & Gallagher, 2010). The substitution of white or whole-wheat flour with spelt, buckwheat or amaranth flour increases the nutritional and functional value of products, which, if consumed regularly, have a positive impact on human health.

In the previous testing (Vujić, Ačanski, Bodroža-Solarov, Hristov & Krunić, 2012) of samples of small grains (wheat, barley and triticale), we noticed that liposoluble (hexane) extracts can be successfully used for fast and secure detection of flour origin. Using the samples of cereals and pseudocereals in this paper, we examined the possibility of distinguishing flour origin on the basis of ethanol soluble ingredients. In the previous testing (Vujić et al., 2012), the samples used were easily soluble non-polar triglycerides. In this paper, we used monosaccharides, their alcoholic counterparts and disaccharides extracted from defatted flour by simple extraction with ethanol.

The content of carbohydrates in bread wheat flours is commonly within the following limits: starch 64–74%, soluble sugars 2–4%, cellulose 0.1–2% and pentosans 1–5% (Djaković, 1997). The sugar content in spelt samples was found to be more variable than in wheat samples, but the number of samples that were investigated is limited. With regard to free sugars, there is no difference in the total concentration between spelt and modern wheat (Escarnot, Jacquemin, Agneessens & Paquot, 2012). Buckwheat seeds contain a type of soluble carbohydrates called fagopyritols (Alvarez-Jubete et al., 2010, Steadman et al., 2000). Soluble sugars include monosaccharides and disaccharides, and play certain roles in the process of bread making (Nandini & Salimath, 2001). In amaranth flours, sucrose was the major sugar followed by raffinose. Inositol, stachyose, and maltose were found in small amounts in most of the samples (Becker et al., 1981).

Sugars also play a role in the process of bread baking since they caramelise at higher temperatures, turn the bread crust to brown colour and affect its properties, appearance and flavor.

Soluble mono- and disaccharides are present in flour and contribute to the rise of the dough in the first stage of fermentation. Either present in the flour, added to the dough or produced in the dough during fermentation, sugars are used as substrate which the yeast ferments and frees into carbon (IV)-oxide and alcohol. Regardless of the origin, the presence of sugar in the dough affects the porosity, structure and appearance of breadcrumbs.

The purpose of this study is to analyse the flour ethanol soluble extract composed of soluble sugars. The following spices have been analysed: seven types of winter wheat (Simonida, Dragana, NS-40S, Pobeda, Ljiljana, Zvezdana and Arija), three types of spelt (Austrija, Eko-10 and Nirvana), three types of amaranth (2A, 16A and 31A) and nine types of buckwheat (Godijeva, Bambi, Darja, Francuska, Prekumurska, Češka, Čebelica, Novosadska and Spacinska).

The objective of the paper is to determine a new method for detecting the flour origin of cereals and pseudocereals using the GC–MS chromatography and cluster analysis of the ethanol soluble extract.