Degradation of tocopherols during rapeseed storage in simulated conditions of industrial silos

Abstract

A b s t r a c t. The investigations consisted in laboratory simulation of conditions prevailing in the real ecosystem in an industrial rapeseed storage facility. The aim of the study was to assess the impact of temperature, moisture, and static pressure on degradation of tocopherols contained in rapeseed. Rapeseed varieties with high oil content were analysed in the investigations. Samples of seeds with 7, 10, 13, and 16% moisture levels were stored at a temperature of 25, 30, and 35°C in specially designed airtight pressure silos for storage in controlled conditions. During the storage, the seeds were subjected to overpressure in the range of 20-60 kPa. The seeds were stored in these conditions for 28 days. It was demonstrated that primarily moisture induced the greatest loss of the total content of tocopherol and its α-T and g-T homologues, followed by temperature and, to a lesser extent, pressure. In addition, the results obtained showed that, in the case of seeds characterised by higher moisture levels (13 and 16%), an increase in the storage temperature in the range of 25-30°C rather than 30-35°C intensified tocopherol loss more efficiently.K e y w o r d s: rapeseed, postharvest, storage, tocopherols INTRODUCTIONOver the last 20 years, the annual rapeseed production has increased and reached 72.5 million tons, with 25.5 million tons produced in Europe. With the annual production rates of 2.7 million tons, Poland is one of the leading producers of rapeseed in Europe (http://www.faostat.fao.org). For many years, rapeseed has been the object of many research programmes focused on improvement of the species. The ongoing research has led to development and introduction for cultivation of the so-called double-zero varieties with reduced contents of not only erucic acid (<2%), but also glucosinolates. The investigations also resulted in development of varieties with desired proportions of fatty acids and increased levels of biologically active compounds eg sterols and tocopherols. Among the available types of oil, rapeseed oil is characterised by the most optimal proportion of omega-6 and omega-3 acids recommended by nutritionists (Booth and Gunstone, 2004; Gunstone 2004, Rękas et al., 2015). Current technologies of phytosterol pathway engineering can provide a two-to threefold increase in the phytosterol levels of oil seeds (Meyer et al., 2009). Currently, rapeseed is a valuable raw material for production of oil (Rusinek et al., 2012;Wroniak, 2012;Wroniak and Rękas, 2015). The by-products obtained during oil production can be used as valuable high-protein feed (Gornas, 2015).The quality of rapeseed oil depends primarily on the condition of seeds used in production; therefore, seeds should be properly preserved after harvest. Rapeseed harvested in Poland usually exhibits a moisture level of 7-17 and 80-90% of the raw materials require cleaning and drying . In Poland, it is recommended that rapeseed intended for long-term storage should be dried to a moisture level of 7% (Kasprzycka et al., 2010). After the dryin...

The effect of drying on the native tocopherol and phytosterol content of Sinapis alba L. seeds

“…in black‐seeded mustard seeds was also markedly lower (39.4 mg kg −1 oil for the α‐T homologue and 414 mg kg −1 oil for the β + γ‐T homologue) than in white mustard seeds. The total tocopherol content of oil produced from the tested white mustard seeds was also much greater than in the oil from seeds of either black‐seeded and yellow‐seeded rape . However, the ratios of individual tocopherol homologues were different in rapeseed oil, with the γ‐T homologue accounting for 57–62% total tocopherol content, while the α‐T homologue accounted for 36–41% .…”

“…The flow rate was 1.0 mL min −1 . The fluorometric detector (Waters 474) worked at an excitation wavelength of 295 nm and an emission wavelength of 330 nm . The tocopherols (α‐T, β‐T, γ‐T, δ‐T) were identified by comparing retention times, while the concentrations were calculated by comparing the area values with those of external standard tocopherols (Merck, Darmstadt, Germany).…”

Effect of self-heating on the processing quality of rapeseed

“…Moreover, it is the increase in humidity from 7 to 9% that causes an eight-fold increase in the intensity of the processes. What is more, a study by Gawrysiak-Witulska et al (2016) on the losses of the total tocopherol content, showed that moisture had the greatest impact. This was followed by temperature, while pressure had a slight effect.…”

Effects of Storage Temperature and Duration on Bioactive Concentrations in the Seed and Oil of Brassica napus (Canola)

“…The seed was then transferred into white polypropylene containers (500 mL) with a screw lid, containing the same headspace volume in each, and placed into containers in the respective treatment conditions (Table ). Moisture was kept to a minimum during the study since seed with moisture levels above 8% are rejected by seed processors, due to the risk of seed spoilage, and spontaneous combustion with silo storage of seed with high moisture . This was achieved by the use of dessicant sachets in all seed samples throughout storage, and the testing of seed moisture at each time of analysis.…”

“…Previous studies have investigated the effects of: Short‐term storage and excessive heating, and varied temperatures with high moisture content, on phytosterol composition in vegetable oils. Tocopherol composition during seed storage has been investigated relative to temperature and moisture extremes, and in oil, relative to temperature and oxygen exposure . Similarly, increases in oxidative stability and the subsequent losses in tocopherols were observed in rapeseed stored in varied conditions over 24 months, with the greatest losses occurring at higher storage temperatures .…”