Influence of thermal treatment on phenolic compounds and antioxidant properties of oak acorns from Serbia

The aim of the present work was to investigate and compare phenolic compounds and antioxidant activity of methanol extracts of Quercus robur and Quercus cerris acorn kernels obtained before and after thermal treatment. Content of total phenolics, tannins, non-tannin phenolics and flavonoids was determined spectrophotometrically and content of gallic acid with HPLC. Antioxidant activity of the samples was assayed through FRAP (Ferric Reducing Antioxidant Power), DPPH scavenging test and inhibition of Fe²⁺/ascorbate induced lipid peroxidation. Extracts of native and thermally treated kernels showed high antioxidant activity, with extracts of thermally treated kernels being more active than extracts of native ones. Hydrolysable tannins and gallic acid were identified in all samples. Non-tannin phenolics, including gallic acid, were present in significantly higher quantities in thermally treated samples, whilst tannin content decreased. This indicates that during thermal treatment hydrolysable tannins were degraded. As the result of this degradation and consequent increase of non-tannin phenolics content, and amongst them especially gallic acid, thermally treated samples possess higher antioxidant activity than do the native ones. The obtained results have provided further grounds for establishing Q. robur and Q. cerris acorn kernels as a source for functional food preparation.     

Antioxidant activity,fatty acids and phenolic acids compositions of potato peels

The effects of freeze-dried extracts from the peels of six potato varieties as antioxidants in pure soy oil were investigated using the active oxygen method (AOM) procedure, carotene bleaching and linoleic acid oxidation experiments on thin-layer chromatography (TLC) plates. At 9 h under AOM conditions, 20 g soy oil treated with 0.05 g of these extracts attained lower peroxide values (PV, 22.0-28.0 meq kg^?1) than the control oil sample (PV, 109.0 meq kg^?1) indicating very strong antioxidant activities. Oils treated with the same amount of tertiary butylhydroquinone, butylated hydroxyauisol-butylated hydroxytoluene mixture and rosemary extract attained PV of 10, 19.0 and 16.0 meq kg^?1, respectively. Results of the carotene bleaching and linoleic acid oxidation experiments on TLC plates indicated that the antioxidant activities of these extracts were due to the presence of phenolic acids. Among the phenolic acids separated and identified by both high-performance liquid chromatography and TLC, chlorogenic, proto-catechuic and caffeic acids were predominant and appeared to be mainly responsible for the strong antioxidant activities of the extracts. Peels from the red potatoes contained more polyphenols than those from the brown-skinned varieties, but their oil contents were similar.     

Isolation,identification and quantification of unsaturated fatty acids,amides, phenolic compounds and glycoalkaloids from potato peel

Eleven compounds were isolated from potato peels and identified. Their structures were determined by interpretation of UV, MS, 1D, and 2D NMR spectral data and by comparison with reported data. The main components of the potato peels were found to be chlorogenic acid and other phenolic compounds, accompanied by 2 glycoalkaloids, 3 low-molecular-weight amide compounds, and 2 unsaturated fatty acids, including an omega-3 fatty acid. The potato peels showed more potent radical scavenging activity than the flesh. The quantification of the 11 components indicated that the potato peels contained a higher amount of phenolic compounds than the flesh. These results suggest that peel waste from the industry of potato chips and fries may be a source of useful compounds for human health.     

几种木本植物种子油的理化性质及脂肪酸组成分析

对侧柏籽、油松籽、核桃、漆树籽四种木本植物种子油脂含油率及理化性质进行了测定,并采用气相色谱法对其脂肪酸组成进行了分析。结果表明,四种种子油的不饱和脂肪酸含量都高达80%以上,其中,侧柏籽油含有高达45.53%的亚麻酸,具有非常高的经济价值。      

Antioxidant properties of commercial wild rice and analysis of soluble and insoluble phenolic acids

To investigate the antioxidant properties of commercial wild rice, identify and quantify soluble and insoluble phenolic acids in wild rice whole grain, the alkaline hydrolysates from crude methanol extracts (soluble fraction) and residues (insoluble fraction) were separately analysed by high performance liquid chromatography (HPLC) coupled with photodiode array detection (PAD) and quadrupole-time of flight (Q-TOF) mass spectrometry (LC–MS). The antioxidant activity of wild rice methanol extract was found to be up to 10 times greater than that of white rice (control sample) according to their 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and oxygen radical absorbance capacity (ORAC). Ferulic acid was found as the most abundant phenolic acid (up to 355 mg/kg) followed by sinapic acid in wild rice. They both occurred mainly in the insoluble form. Other monomeric phenolic acids present in wild rice consisted of p-coumaric, vanillic, syringic, and p-hydroxybenzoic acids, along with two phenolic acid aldehydes (p-OH-benzaldehyde and vanillin). They were present in both soluble and insoluble forms. Phenolic acid dehydrodimers are cell wall bound and only appeared in the insoluble fractions featured by diferulic acids (DiFA) and disinapic acids (DiSA). The chemical structures of DiFA included 8-8′, 5-5′, 8-O-4′, and 8-5′ (benzofuran form) coupled dimers, with 8-O-4′ as the predominant form (up to 34 mg/kg). DiSA only appeared as 8-8′-coupled products with the linear isomers in the most quantities (up to 19 mg/kg). The DPPH free radical scavenging activities of soluble and insoluble fractions suggest that the antioxidant activity of wild rice is partially attributed to its phenolic acid profile.     

枳椇籽油理化性质及其脂肪酸分析

对枳椇籽油的理化特性进行了测定,并利用气相色谱-质谱(GC-MS)联用技术对枳椇籽油的脂肪酸组成进行了分析和鉴定.结果表明:枳椇籽舍油率为8.0%,其中不饱和脂肪酸占87.46%以上,亚麻酸含量高达45.56%;枳椇籽油折光指数(20℃)为1.478 9,相对密度(d204)0.918 7,碘值(Ⅰ)170.7 g/100 g,皂化值(KOH)178.9 mg/g.枳椇籽油具有较高的营养价值.     

Compositions of phenolic compounds,amino acids and reducing sugars in commercial potato varieties and their effects on acrylamide formation

BACKGROUND: Potato is consumed as an important source of carbohydrate and other nutrients as well as a good source of phenolics. Acrylamide is a potential carcinogen formed during frying of potato products. This study investigated the compositions of phenolic compounds, amino acids and reducing sugars in 16 commercial potato varieties from eight countries and analysed the relationships between these compositions and the levels of acrylamide generated by heating (185 °C, 25 min) potato powders. RESULTS: Major phenolic compounds in the tested potato varieties were identified as hydroxycinnamoylquinic/hydroxycinnamoyl derivatives by liquid chromatography/mass spectrometry. Great variations in the contents of phenolic compounds, free reducing sugars and amino acids as well as wide variations in acrylamide concentration were found among the different potato varieties. Correlation analysis revealed that fructose (r = 0.956***), glucose (r = 0.826***) and asparagine (r = 0.842***) were positively correlated with acrylamide formation. Interestingly, it was observed that higher levels of phenolic compounds were related to lower levels of acrylamide (r = ? 0.692*). CONCLUSION: Careful selection of potato varieties with lower levels of fructose, glucose and asparagine and higher levels of phenolic compounds may mitigate acrylamide formation during thermal processing of potato products. Copyright © 2010 Society of Chemical Industry     

Effect of processing techniques on antioxidative enzyme activities, antioxidant capacity, phenolic compounds, and fatty acids of table olives

In this study, olive fruits (Olea europeae cv. Gemlik) of the most common sources of table olives in Turkey were used. Total polyphenol content (TPC), antioxidant capacity (AC), and antioxidant enzymes (catalase, CAT; ascorbate peroxidase, APX; and glutathione reductase, GR) of table olives were compared by 4 different methods of ripe table olive processing. Results revealed that TPC of the processed olives ranged from 117.44 to 418.69 mg gallic acid equivalents/g fresh weight (f.w.). The highest AC as mg Trolox equivalents of 189.58/g f.w. was obtained from unprocessed black olives. CAT, APX, and GR activities of unprocessed olives were higher than those obtained in all processed olives. In conclusion, TPC, AC, and antioxidant enzyme activities are strongly affected by fruit ripening and processing in table olives of ‘Gemlik’ cultivar. In addition, the best processing technique is untreated black olives in brine for antioxidant properties.     

成熟度指数对不同品种橄榄油脂肪酸、 酚类化合物及风味属性的影响

以甘肃省陇南市油橄榄研究所种质资源基因库的‘城固32号’和‘莱星’油橄榄果为原料提取橄榄油,运用GC-MS、HPLC和E-Nose对不同品种与不同成熟度指数的橄榄油脂肪酸、酚类化合物及风味属性进行检测分析,以探究成熟度指数与不同品种橄榄油品质的关系。结果表明：随着成熟度指数的增大,‘城固32号’橄榄油中的硬脂酸、油酸、亚麻酸、饱和脂肪酸（SFA）含量及单不饱和脂肪酸/多不饱和脂肪酸（MUFA/PUFA）和油酸/亚油酸值呈下降趋势,亚油酸和不饱和脂肪酸（UFA）含量呈上升趋势,‘莱星’橄榄油中油酸和UFA含量及MUFA/PUFA和油酸/亚油酸值呈上升趋势,而亚油酸、亚麻酸和SFA含量呈下降趋势;油酸/亚油酸和MUFA/PUFA值在2个品种间存在差异,可作为鉴别‘城固32号’和‘莱星’橄榄油的依据;2个品种橄榄油中酪醇和总酚含量总体呈下降趋势,香草酸和木犀草素含量总体呈上升趋势,而羟基酪醇含量在‘城固32号’中总体逐渐减少,在‘莱星’中总体逐渐增加,木犀草苷含量在2个品种中保持稳定;风味物质的E-Nose信号响应值在2个品种中均显著减小。利用橄榄油中脂肪酸和酚类化合物的组成与含量以及风味属性的信号响应值差异结合主成分（PCA）分析可有效鉴别和区分不同成熟度指数的‘城固32号’和‘莱星’橄榄油。