Application of Chromatographic and Thermal Methods to Study Fatty Acids Composition and Positional Distribution, Oxidation Kinetic Parameters and Melting Profile as Important Factors Characterizing Amaranth and Quinoa Oils

Magdalena Wirkowska-Wojdyła,Agata Górska,Joanna Bryś,Ewa Ostrowska-Ligęza

doi:10.3390/app12042166

Abstract

Amaranth and quinoa are classed as pseudocereals that do not belong to the grass family, meaning they are not technically a grain. Both of them are seeds with tremendous nutritional value; compared to other cereals, they contain much more fat. The aim of the study was to present the parameters characterizing thermal properties of amaranth and quinoa oils, such as: oxidation induction time, oxidation kinetic parameters, and melting profile. In isolated oils, the peroxide value, oxidative stability by the Rancimat test (in 120 °C) and the pressure differential scanning calorimetry (PDSC) method (at 100, 110, 120, 130, 140 °C), fatty acids composition, and their distribution between the triacylglycerol positions were determined. The kinetic parameters of the oxidation process (activation energy, pre-exponential factor, and reaction rate constants) were calculated using the Ozawa–Flynn–Wall method and the Arrhenius equation. To measure the melting profile, the differential scanning calorimetry (DSC) method was used. Both types of seeds are a good source of unsaturated fatty acids. Induction time of oxidation suggests that amaranth oil may have better resistance to oxidation than quinoa oil. The melting characteristics of the oils show the presence of low-melting triacylglycerol fractions, mainly containing unsaturated fatty acids, which means that a small amount of energy is required to melt the fats.

Highlights

Amaranth (Amaranthum) and quinoa (Chenopodium quinoa Willd) are pseudocereals because their seeds resemble real cereals in terms of their composition and function
Two packs of quinoa (Chenopodium quinoa Willd) and amaranthus (Amaranthus cruentus) seeds were purchased in two different retail outlets in Poland in October 2019 in order to avoid the same lots of seeds
Our results showed that quinoa oil contained more polyunsaturated fatty acids and less saturated fatty acids than amaranth oil

Summary

Introduction

Amaranth (Amaranthum) and quinoa (Chenopodium quinoa Willd) are pseudocereals because their seeds resemble real cereals in terms of their composition and function. Interest in quinoa and amaranth stems from their nutritional value, higher than cereal grains like corn, oats, wheat, and rice. The quinoa seeds contain exogenous amino acids such as: lysine, arginine, histidine, and methionine [5]. These amino acids are most often found in small amounts in cereal grains and legumes [6]. Quinoa seed protein is characterized by a more balanced amino acids composition than wheat protein. Amaranth seed protein contains all the amino acids essential for the human body, surpassing soybean protein. The biological value of amaranth protein is higher than milk proteins, so amaranth can be used to produce milk replacement products for people intolerant to lactose [7]

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