Comparison of the sensory properties, physico-chemical quality and oxidative stability of selected cold-pressed oils

Celem pracy było porównanie cech sensory cznych, fizyko-chemicznych i stabilności oksydatywnej wybranych olejów tłoczonych na zimno oraz ocena ich trwałości w warunkach chłodniczych. Do badań użyto jedenastu rodzajów olejów: lnianego wy-sokolinolenowego, lnianego niskolinolenowego, rzepakowego, krokoszowego, makowego, z awokado, z nasion dzikiej róży, z prażonych pestek dyni, z orzechów arachidowych, brazylijskich oraz włoskich. W olejach oznaczono stopień hydrolizy, pierwotny i wtórny stopień utlenienia, barwę i stabilność oksydatywną (Rancimat w 120°C). Spośród porównywanych olejów najwyższym stopniem akceptacji konsumenckiej charakteryzował się olej z orzechów arachidowych, a najniższym olej z awokado. Stwierdzono, że analizowane oleje spełniały stawiane im wymagania dotyczące podstawowych wyróżników jakości, poza olejami z awokado i krokoszowym. Najwyższą stabilnością oksydatywną charakteryzował się olej arachidowy (20,80 h), najniższą natomiast lniany wysokolinolenowy (1,07 h). Po przechowywaniu olejów w warunkach chłodniczych odnotowano, że zmiany spowodowane hydrolizą w niewielkim stopniu dotyczyły tych produktów, natomiast utlenianie zachodziło intensywnie.The aim of the study was to compare the sensory characteristics, physical, and chemical quality as well as oxidative stability of selected cold-pressed oils. Eleven types of oils were investigated, including: high-linolenic flaxseed, low-linolenic flaxseed, saf-flower, poppy seed, avocado, rose hip seed, roasted pumpkin seed, peanut, Brazil nut and walnut. These oils (fresh and after storage under refrigeration) were analyzed in the field of intensity of: the sensory characteristics by profiling, an assessment of the level of consumer acceptance, the level of lipid hydrolysis, primary and secondary oxidation state, color and oxidative stability (Rancimat test at 120°C). It was stated that peanut oil was characterized by the highest degree of consumer desirability. Further in terms of consumer desirability were (in descending order): roasted pumpkin seed, walnut, low-linolenic flaxseed, Brazil nut, rapeseed, poppy seed, safflower, high-linolenic flaxseed, rose hip seed oils. The lowest degree of acceptance was a characteristic of avocado oil. The darkest of oils were: roasted pumpkin seed and avocado, and the brightest oils were: Brazil nut and walnut. It was found that all the analyzed oils fulfil requirements on the basic parameters. Acid value for all oils was low (from 0.35 to 3.35 mg KOH∙g-1). On the other hand, peroxide value was high (1.29 to 32.60 meq O2∙kg-1), but met the standard (PV < 15), with the exception of oils: safflower (15.30 meq O2∙kg-1) and avocado (32.60 meq O2∙kg-1). Secondary oxidation state of oil was very low (AnV from 0.27 to 4.63). However, there was a high level of conjugated dienes (from 1.20 to 5.00) and trienes (from 0.17 to 1.49). The K232 = 2.50 was exceeded in four oils: Brazil nut, pumpkin seed, safflower and avocado. K270 = 0.22 has been exceeded only in the case of 3 oils: poppy seed, pumpkin seed and Brazil nut. On the basis of the Rancimat test, it was found that the lowest oxidative stability was a characteristic of high-linolenic flaxseed oil (1.07 h), while the highest oxidative stability was a characteristic of peanut oil (20.80 h). After 2 months of storage under refrigeration, degree of lipid hydrolysis remained at a constant low level, while the primary and secondary oxidation state increased, especially intensively in cases of: rosehip, avocado, pumpkin seed, walnut, poppy seed, and rapeseed, which resulted in exceeding the values specified in the Codex Alimentarius