Lipid stability study in low lipase oat lines

Abstract

Oat is a cereal that contains high lipid content when compared to other cereals and is a potential oil crop. Oats also have high content of lipase enzymes when compared to other cereals, that causes hydrolytic rancidity which causes the soapy bitter taste that may develop in oats. Therefore, oats that are intended for human consumption are heat treated to inactivate lipase enzymes and thus, to improve storage properties by minimizing rancidity. However, heat treating the oats have adverse effects on other molecules in the seed such as vitamins and proteins. It is also a time and energy consuming step. An alternative way to handle this problem would be to develop oat with decreased lipase content, so that lipid degradation is minimized even without heat treatment. As part of a ScanOats project, several low lipase oat lines have been identified from the EMS-mutated population developed by the company Crop Tailor. However, it is not known to what degree the lipase activity of the oat kernels needs to be reduced to significantly lower lipid degradation into free fatty acid during storage. Thus, this project was aimed to evaluate the relationship between lipase activity and free fatty acid formation during short time storage. In this project, a short lipid stability study (two weeks) of Belinda (control) and four selected low (LL) and one high (HL) lipase oat lines cultivated in Lönnstorp 2020 was carried out.
Lipase activity was tested at different pHs and found to be similar at respective pH throughout the study period, with a trend to be higher in the fresh samples compared to samples stored for 14 days. Lipase activity in all tested lines except HL-01 was higher at pH 7 and pH 6.5 than at pH 7.5. The FFA levels tested increased during the storage in all lines. Highest levels were found in Belinda and the lowest in the low lipase line LL-01. In LL-01, no increase in FFA was seen between day 7 and 14. Also in LL-02 and LL-04, the FFA accumulation over time was lower than in Belinda but higher than in LL-01 at day 14. LL-01 is therefore the most promising line when it comes to reduced FFA. The dominating FFA that accumulated were Palmitic acid (C16:0), Linoleic acid (C18:2), Oleic acid (C18:1).
The total lipid content remained stable in Belinda and all the oat lines with only slight changes through the study. In contrast, the peroxidase values (PV) increased significantly after two weeks in all samples, although from a very low level. The Belinda control had the lowest PV value both at the start and after two weeks with only a very small increase. Since oat are intended to be stored for longer time, it is important to study these characteristics also for a longer storage time to get a more precise picture of what is going on.

Keywords: Oats, Lipase, Free fatty acid, total lipid, peroxidase value

Popular Abstract

Oat is a whole grain food that has become a very popular health food consumed all around the world. It is a source of fiber, unsaturated fatty acids, vitamins, antioxidants, and minerals and are also identified as gluten- free whole grains. The high demand for oat and its products leads to its high production rate and processing and storage. Therefore, storage of oats for longer time is of importance to feed the large population on earth consistently. But does storage affect the quality of oats? Unfortunately, yes! During storage of oat, off flavors and bitter taste may arise, which makes the oat unsuitable for human consumption. This formation of bitter taste and off flavors is called rancidity and is due to changes in the lipids.
A group of enzymes called lipases play a vital role in the decrease of oat quality during storage. Lipase converts the oat lipids into unwanted free fatty acids Therefore, a heat treatment is carried out to deactivate these enzymes. This heat treatment, that is performed on oats for human consumption, minimize rancidity during storage but has other disadvantages. The heat treatment can reduce the antioxidant and vitamin content in the oats and is also costly and time-consuming. So, what else can be done to increase the storage stability of oats? The solution may be the introduction of oat varieties that have low lipase content.
In this study, oat lines with low and high lipase content have been milled and stored for two weeks, with samples studied at several different time points. The amount of lipase present was estimated by measuring enzyme activity. Other important components investigated was lipid content and amount of free fatty acids. These two factors were assessed using gas chromatography. Furthermore, rancid products formed due to the oxidation of oat lipids was analyzed by determining the peroxidase value. Altogether, this project emphasis the effort to come up with an oat variety that has a longer shelf-life with no need for post-harvest treatment. The study concludes that several of the low lipase oat lines had lower content of free fatty acids after the storage than the control, strengthening the support for low-lipase oat as a solution for oat storage problems. However, it is important to study these characteristics also for a longer storage time to get a more precise picture of the rancidity development in oats.

• author: Jaison, Chinnu Ann
• supervisor: Sofia Marmon
• organization: Pure and Applied Biochemistry
• course: KBKM01 20211
• year: 2021
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Oats, Lipid oats, Rancidity, lipase, Biotechnology, Free Fatty Acid, Total lipid, Gas Chromatography, food and technology, biochemistry
• language: English
• id: 9064476
• date added to LUP: 2021-09-07 09:34:50
• date last changed: 2021-09-07 09:34:50