Phenolic compounds from different plant sources, like fruits, vegetables, cereals, and herbs, have been excessively studied and widely used in different industrial areas, including food, medicine, ...and pharmaceuticals. Recently, special attention has been paid to the phenolic compounds of plant oils that have recently been found to vastly affect the oxidative stability of these products.
This paper reviews the contents and types of phenolic compounds in their initial forms in plant oils and methods of their determination. Also, their impact on the oxidative stability of oils is discussed.
The total free content of phenolic compounds and the phenol profile in plant oils are very diverse and depend on the oil source and production method. Generally, the main oily source of these compounds is rice bran and olive fruits. Their high amounts can also be found in rapeseed, flaxseed, grapeseed, and pumpkin oils. The main groups of phenolic compounds in oils are phenolic acids and flavonoids. Additionally, lignans, secoiridoids, and phenolic derivatives are identified in some oils. The two main methods for the determination of phenolic compounds in oils include the spectrophotometric and chromatographic ones. The general principles of these assays are often modified by various authors to adapt them to research conditions. Available literature data confirmed the strong antioxidative activity of some phenolic compounds found in oils. However, further studies are needed to better understand the mechanism of their protective action on oils, especially under natural storage.
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•Phenolic composition of oils varies depending on raw material and production method.•Current analytical approaches for determining phenolics in oils are discussed.•Studies on efficiency of phenolics as oil oxidation inhibitors are demonstrated.•Further tests are needed to better explain phenolics protective action on oils.
•4-Vinylguaiacol (4-VQ) and 4-vinylsyringol (4-VS) were added to stabilize oils.•4-VQ was more effective antioxidant than 4-VS.•Induction period (IP) increase was the lowest for olive oil and the ...highest for flaxseed oil.•4-VQ in similar degree affected IP of refined and cold-pressed rapeseed oil.
The aim of the work is to compare the antioxidant activity of 4-vinylguaiacol (4-VQ) and 4-vinylsyringol (4-VS) added to stabilize three (flaxseed, olive and rapeseed) commercial oils. The phenolics were added at concentration of 20, 40 and 80mg per 100g of oil. The oils were oxidized in a Rancimat test at 110°C. The linear dependences between the concentrations of each of these compounds and the induction period (IP) were found. Generally, 4-VQ was more effective, since the determined IP increase after its addition was from 5 to 25-fold higher than for the same addition of 4-VS. The highest increase was noted for flaxseed oil, for which 80mg 4-VQ addition per 100g of oil resulted in 50% IP increase. The highest absolute values of IP were reached by extra virgin olive oil, naturally abundant in phenolic compounds and with the lowest fatty acids oxidation index.
•Cold-pressed oils with sinapic and ferulic acids vinyl derivatives were oxidized.•Phenolic vinyl derivatives increased sterols, carotenoids and squalene retention.•Ferulic acid vinyl derivative ...inhibited α-linolenic acid loss.•Ferulic acid vinyl derivative can be use as a food additive for oil stabilization.
In the western diet there is an oversupply of n-6 fatty acids. This adverse trend can be balanced by the consumption of rapeseed and flaxseed oils rich in α-linolenic acid (n-3). However, the high share of this fatty acid contributes to low oxidative stability of oil. Oxidation decreases n-3 fatty acid and other bioactive compounds contents, which adversely affects oil nutritional value. In this study, the impact of ferulic and sinapic acids vinyl derivatives on the fatty acids and oil terpenoids (sterols, tocols, carotenoids, squalene) retention at the end of induction period during accelerated oxidation of rapeseed and flaxseed cold-pressed oils was investigated. It was found that the use of 4-vinylsyringol (4-VS) or 4-vinylquaiacol (4-VQ) increased the retention of intact sterols and carotenoids (at least 2-fold) and squalene (at least 4-fold). The 4-VQ addition also inhibited the α-linolenic acid loss. Unfortunately, both phenolic derivatives favoured α-tocopherol decay in rapeseed oil.
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•Lyophilized edible flowers are a valuable source of phenolic compounds.•Extract from 23 lyophilized edible flowers were added to cold-pressed oils.•The flower extracts stabilized ...more effectively chia seed oil than flax seed oil.•Nasturtium and marigold scattered extracts highly inhibited the oxidation of both oils.
This study aimed to evaluate and compare the effect of methanolic extracts from 23 lyophilized Polish edible flowers on the oxidative stability of two cold-pressed oils rich in omega-3 fatty acids. Two popular oils (flax and chia seed oils) were used in the study and characterized for their chemical composition, quality and oxidative stability. Hydro- and lipophilic components, and antioxidant activity were determined in the flower extracts. The effectiveness of the edible flower extracts in oxidative protection of cold-pressed oils was evaluated in the Rancimat test. The edible flower extracts differed significantly in their composition and antioxidant activity. Among the extracts, the richest source of phenolic compounds were those obtained from red begonia (996.80 ppm), red geranium (1028.16 ppm), and small leaved lime (1003.62 ppm) flowers; whereas red begonia and red geranium flower extracts were also found to be valuable sources of flavonoids, 343.70 and 307.34 ppm, respectively. The extracts from lyophilized edible flowers had a low content of lipophilic pigments (0.97–9.01 ppm for chlorophylls and 0.03–12.34 ppm for carotenoids), while the content of tocopherols varied greatly (0.70–193.34 ppm). Most of the analyzed extracts were characterized by a high DPPH radical inhibition value (>10 µM TE/mL). Almost all studied edible flower extracts improved oxidative stability of the cold-pressed flax and chia seed oils. More favorable effects were observed in chia seed oil, in particular after the addition of extracts from nasturtium, marigold scattered, dog rose, and daylilies flowers (the changes were more than 50% higher compared to the control sample).
The aim of the study was to assess the relationships between cocoa mass percentage declared by producer and color, free phenolic compounds content and antioxidant capacity of chocolate bars. The ...research materials were commercially available 2 dessert (with 30 and 50% of cocoa mass) and 10 bitter chocolate bars (with 40–90% of cocoa mass). The scope of analysis included determining chocolate bars surface color using digital image analysis, content of free phenolic compounds (total, flavonoids and proanthocyanidins) using spectrophotometric methods and antioxidant capacity using the Cuprac method.
Based on the results, it was generally found that bitter chocolate bars were characterized by a darker color and a higher content of free phenolic compounds (252.38–703.13 mg/100 g), including flavonoids (29.01–89.55 mg/100 g) and proanthocyanidins (52.23–224.47 mg/100 g), compared to dessert chocolate bars (241.70, 38.58 and 58.99 mg/100 g on average, respectively). The study showed that the cocoa mass content in the chocolate bars was strongly positively correlated with the phenolic compounds content (in particular flavonoids) and the antioxidant capacity. On the other hand, these properties of the chocolate bars were less dependent on the surface color.
Flaxseed oils contain significant amounts of unsaturated fatty acids and, consequently, are susceptible to oxidative process. Additionally, inadequate conditions of storage result in the ...intensification of unfavorable processes. This problem is becoming more and more serious due to the high intensity of illumination of shop display cases and storage rooms, as well as the exposure to sunlight. Although literature data suggests that light may be an even more important oxidizing agent than oxygen, experiments are mainly focused on the oxidation progress in oils from varied raw materials or the changes in oil characteristics under different storage conditions. The aim of the study was to investigate the effect of the initial state of 30 commercial cold-pressed flaxseed oils on oxidative stability and oxidation product formation during storage under simulated store conditions (one-month at ambient temperature with light exposure). The oil quality was analyzed qualitatively (characteristic quality values, content of conjugated fatty acids, induction period, color parameters) and quantitatively (content of water and bioactive compounds, fatty acid composition). Oxidation progress in the oils was monitored by the characteristic quality values, content of conjugated fatty acids and color parameters.
It was shown that commercially available cold-pressed flaxseed oils were generally good quality with similar color parameters and fatty acid composition, but mostly varied in terms of carotenoids, chlorophylls and phenolic compounds. Storage with light exposure caused the deterioration of the oil quality, and at least a 1.0-fold increase in acid and anisidine values and at least a 24.8-fold increase in peroxide value were determined. Also, the color of all oils changed after storage, and the calculated total color differences (ΔE) were in the range of 0.2–8.7. The results highlighted that the formation of oxidation products in flaxseed oil during storage in light resulted mainly from its initial quality indices. In turn, the induction period tested by Rancimat was dependent on the fatty acid percentages and total phenolic compound content. In conclusion, the Rancimat test is a poor indicator of the oxidative stability of oils under storage at ambient temperature with light exposure.
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•Content of bioactive compounds in commercial cold-pressed flaxseed oils is varied.•Linolenic and oleic acids and phenolic compounds mainly affect oil induction period.•Initial quality determines formation of oxidation products in oils exposed to light.•Oxidizability indices are not good predictors of oxidation rate during oil storage.
Recently, the most commonly used cooking oils in the world are obtained from corn germ, soybean, sunflower and rape seeds. Also, refined flaxseed oil is preferred for low-heat cooking in some ...countries. Use these oils instead of solid fats (including butter, shortening, lard and margarine) and tropical oils (including palm and coconut oil) can be healthy choice, because of lower saturated fat content. Unfortunately, repeated or high-temperature heating may result in oil decompose to form unwanted hazardous substances which can pose harmful effects to the health. The well-known natural method to limit oil oxidation is the used of herbs and spices, which also can improve the taste and aroma properties of food. The aim of the study was to evaluate the effect of added herbal extracts on the oxidative stability of two cooking plant oils (refined rapeseed oil, refined flaxseed oil) during low- and high-temperature heating.
Hydro- and lipophilic extracts were prepared from popular commercial dried herbs (thyme, parsley, caraway, oregano, basil, dill) using 70% methanol and n-hexane, respectively. Cooking plant oils were characterized by quality indices, fatty acid composition and content of bioactive compounds, while in the herbal extracts' composition and content of pigments, total phenolic compounds, flavonoids, tocols and antioxidant capacity were examined. The oxidative stability of cooking plant oils, without and with the addition of herbal extracts, was determined in the Rancimat test at 110 and 150 °C for refined rapeseed oil and 80 and 110 °C for refined flaxseed oil.
It was found that the addition of herbal extracts had varied effect on oxidative stability of flaxseed and rapeseed oils at low- and high-temperature heating. Flaxseed oil was generally well-protected by thyme hydro- and lipophilic extracts regardless of temperature heating (induction period increase by 18–24%). Also, hydrophilic parsley and lipophilic oregano extracts improved this oil oxidative stability at low temperature (induction period increase by 10–17%), while lipophilic extracts from caraway and dill were more effective at high temperature (induction period increase by 20–26%). In turn, all extracts improved the rapeseed oil oxidative stability under low-temperature heating (induction period increase by 11–24%), but they were ineffective during high-temperature heating. The better additives for this oil were both type extracts obtained from thyme and oregano, which were characterized by the highest content of antioxidants, total phenolic compounds and tocopherols, mainly α-tocopherol. The results suggest a greater difference in content of phenolic compounds for extracts obtained by using of different solvents then from different herbs. In turn, the herb type had a strong impact on the content of pigments and tocopherols.
Results confirmed the possibility of using herbal extracts to increase the oxidative stability of cooking plant oils during thermal heating. However, the type of solvent and herb should be adjusted individually to cooking oil type and heating temperature.
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•Hydro- and lipophilic herbal extracts (HE) contained mainly of phenolics and tocopherols.•HE protective action was varied in refined rapeseed (RRO) and flaxseed oils (RFO).•Thyme and oregano extracts were more effective during low-temperature RRO heating.•RFO at high temperature was well-protected by caraway and dill lipophilic extracts.•Thyme and parsley hydrophilic extracts improved RFO stability at low temperature.
Ferulic acid (FA) is a naturally occurring phenolic antioxidant that is widely used in the food, pharmaceutical, and cosmetic industries due to its low toxicity. Its derivatives also find numerous ...industrial applications and may have even higher biological activity than ferulic acid. In this study, the effect of the addition of FA and its derivatives-including vanillic acid (VA), dihydroferulic acid (DHFA), and 4-vinylguaiacol (4-VG)-on the oxidative stability of cold-pressed flaxseed oil and the degradation of bioactive compounds during oxidation was investigated. The results showed that FA and its derivatives affected the oxidative stability of flaxseed oil, but their antioxidant activity depended on the concentration (25-200 mg/100 g oil) and temperature of treatment (60-110 °C). Based on Rancimat test results, flaxseed oil oxidative stability predicted at 20 °C increased linearly with ferulic acid concentration, while its derivatives effectively prolonged the induction time at lower concentrations (50-100 mg/100 g oil). The addition of phenolic antioxidants (80 mg/100 g) generally showed a protective effect against polyunsaturated fatty acids (DHFA and 4-VG), sterols (4-VG), tocols (DHFA), squalene, and carotenoids (FA). The exception was VA, which increased the degradation of most bioactive compounds. It is believed that adding properly composed mixtures of FA and its derivatives (DHFA and 4-VG) can extend the shelf life of flaxseed oil and provide nutritional benefits.
Introduction and aim: Gluten-free diet is a necessary diet in a treatment of gluten-dependent diseases. It means a complete exclusion from the menu of products being a source of gluten. An important ...issue in providing for consumers to choose the right gluten-free food product is the readability of information (about the presence of gluten in the product) and the ease of finding it on the packaging. The legal provisions on the labelling of this type of food require that the label be clearly and legibly formulated (e.g. gluten-free product) in a prominent place on the packaging, which should be helpful for people with celiac disease and gluten allergies to recognize the suitable products. The aim of the article was to evaluate the compatibility of labeling gluten-free food products with current legal provisions based on the review of information on the labels. Brief description of the state of knowledge: The research material was 125 labels of gluten-free products of various producers, which were available on the Masovian Voivodeship market (cereal and breakfast products (60), sugar and confectionery (35), fruit and vegetables products (8), meat and fish products (6), frozen products (4), drinks (2), other products (10)). The analysis included written and graphical information, which was found on the product label. 93 labels were characterized by the presence of 'gluten free product' in a vicinity of the product name. Very often, producers also placed a graphic sign in the form of a 'Crossed Ear' (98), also gave the license code next to the sign (93). On the cereal and breakfast products labels, manufacturers often placed additional written information to improve the product's credibility. Drinks were labelled only 'gluten-free products' (2), which is required by law. Summary: In accordance with the obligation in the regulations, most of the tested product labels met this requirement. Very popular formulation on the labels was a 'gluten-free product', and less often other specified in legal requirements. Only a small percentage of the analyzed product labels could raise doubts about the content of gluten and its safe consumption.
Introduction and aim: Gluten-free diet is a necessary diet in a treatment of gluten-dependent diseases. It means a complete exclusion from the menu of products being a source of gluten. An important ...issue in providing for consumers to choose the right gluten-free food product is the readability of information (about the presence of gluten in the product) and the ease of finding it on the packaging. The legal provisions on the labelling of this type of food require that the label be clearly and legibly formulated (e.g. gluten-free product) in a prominent place on the packaging, which should be helpful for people with celiac disease and gluten allergies to recognize the suitable products. The aim of the article was to evaluate the compatibility of labeling gluten-free food products with current legal provisions based on the review of information on the labels. Brief description of the state of knowledge: The research material was 125 labels of gluten-free products of various producers, which were available on the Masovian Voivodeship market (cereal and breakfast products (60), sugar and confectionery (35), fruit and vegetables products (8), meat and fish products (6), frozen products (4), drinks (2), other products (10)). The analysis included written and graphical information, which was found on the product label. 93 labels were characterized by the presence of 'gluten free product' in a vicinity of the product name. Very often, producers also placed a graphic sign in the form of a 'Crossed Ear' (98), also gave the license code next to the sign (93). On the cereal and breakfast products labels, manufacturers often placed additional written information to improve the product's credibility. Drinks were labelled only 'gluten-free products' (2), which is required by law. Summary: In accordance with the obligation in the regulations, most of the tested product labels met this requirement. Very popular formulation on the labels was a 'gluten-free product', and less often other specified in legal requirements. Only a small percentage of the analyzed product labels could raise doubts about the content of gluten and its safe consumption.
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