# Influence of Cryogenic Grinding on the Nutritional and Antinutritional Components of Rapeseed Cake
## 1 Introduction  
According to the Food and Agriculture Organization of the United Nations (FAO), demand for food will roughly double by 2050 due to the growing world population. One of the biggest challenges will be meeting the growing demand for meat, as it is estimated that meat production will have to increase by over 200 million tons per year [1]. Population pressures aside, environmental considerations and production efficiencies underscore the importance of new high-quality sources of protein for human nutrition, such as plants, for both developed and developing countries. And rapeseed could be a good local source. Rapeseed is used to produce high-quality oil, but the by-products of this production, rapeseed meal and cake, have a high protein value. The balance and bioavailability of amino acids and the digestibility of proteins are comparable to those of soybean meal [2, 3]. In fact, rapeseed cake and meal are the second most important feed source after soybean meal [4] and have the chance to be an economical and sustainable source of protein in food [2]. In addition, research has shown that rapeseed meal has good water and oil binding capacity as well as very good emulsifying and foaming properties, which are of great importance for incorporation into novel functional foods [5]. However, despite decades of research, development of various technologies, and large-scale manufacturing, there are still no commercially available rapeseed cake products for human consumption [2]. The use of rapeseed meal and cake in human nutrition is limited by the presence of antimutrittional components such as glucosinolates, phenolic compounds, tannins, phytates, and hulls [6]. The main concern when using rapeseed meal and cake as food ingredients are glucosinolates. This is a large group of sulphur-containing secondary plant metabolites foundin all economically important varieties of Brassica. There is great diversity among glucosinolates, and more than 120 different compounds have been identified [7]. Although some glucosinolates possess antibacterial and antifungal properties as well as anticancer activity, the antinutritional effects of glucosinolates and their degradation products present in rapeseed meal and cake have limited the use of rapeseed by-products as a food source [8]. They are known to reduce animal growth, cause iodine deficiency, and cause hypertrophy of liver, kidney, and thyroid [7]. In addition, these compounds provide a bitter taste and sulphurous aroma due to their degradation products. Therefore, one of the most important breeding objectives is to reduce the glucosinolate content in the seed to trace amounts [8]. Commercial rapeseed cakes are rich in phenolic compounds, especially derivatives of sinapic acid, which account for about 80-99% of total phenols, mainly in the form of esters and glucosides. Although they are known to be potent free radical scavengers and antioxidants [9], their content in rapeseed meal and cake is up to 30 times higher than in by-products from other seeds. These high concentrations of phenolic compounds may contribute to the dark colour, bitter taste, and astringency of rapeseed meal. In addition, phenols and their oxidized products can form complexes with essential amino acids, enzymes, and other substances, lowering the nutritional value of meal and cake. Another group of phenolic constituents found in canola are condensed tannins. Tannins are complexed phenolic compounds formed by polymerization of flavan-3-ols or flavan-3,4-diols [10]. Similar to phenolic acids, they also have antioxidant activity [11], and they are also of concern due to their ability to bind with proteins. Tannins form complexes with lysine and methionine, making them nutritionally unavailable. Therefore, the phenolic compounds and tannins, as well as their concentrations, are important factors when canola meal is considered a protein source in food formulations [10].