Determination of phytosterol oxides in some food products by using an optimized transesterification method

An increased intake of phytosterols (PS), as well as new products launched on the market enriched with PS and phytostanols, increases the demands for improved analytical techniques. In the present study, a method for the determination of phytosterol oxidation products (POP) was evaluated and optimized. The method included transesterification, enrichment with amino SPE cartridges and quantification by GC. The methodology was evaluated with authentic samples of sito-, campe- and stigma-sterol oxidation products and the linearity and recovery for some POP were >0.95 and 80–120%, respectively. The lowest spiking level determined was 0.5 μg and lower levels could be quantified. In addition, the formation of POP during thermal oxidation of vegetable oils at 180 °C for 0–2 h was studied and increased levels were observed. A commercially available PS ester-enriched margarine was also included in the investigation and the level of POP was 12 μg/g of spread.     

Separation and isolation of β-sitosterol oxides and their non-mutagenic potential in the Salmonella microsome assay

The recent increase in phytosterol-enriched functional food provokes questions concerning the safety of their oxidation products. However, most of the existing toxicity studies have been performed with mixtures instead of single compounds, a consequence of the lack of pure phytosterol oxidation product (POP)-standards.     

食品中植物甾醇氧化物研究进展

植物甾醇作为一种降胆固醇的功能性成分已被广泛用于食品及其配料中,但是其化学结构与胆固醇类似,易受光、热、氧、金属离子等作用,转变成对人体具有潜在危害的植物甾醇氧化物(POPs)。虽然对这种潜在危害还存在争议,但POPs已经引起了人们的关注。本文综合现有国内外有关文献,对POPs的来源分布、形成机理、生理作用及抑制有害POPs生成等几个方面的研究进展进行了总结,并对其研究发展趋势进行了展望。     

Oxidative stability of functional phytosterol-enriched dark chocolate

A dark chocolate containing phytosterols (PS) esters was developed to reduce cholesterol in individuals. However, oxidative instability during chocolate processing and storage could reduce the PS bioactivity. Chocolate bars were prepared containing palm oil (CONT) or 2.2 g of PS (PHYT). All samples were stored at 20 °C and 30 °C during 5 months. A peak of hydroperoxides formation was observed after 60 days at 20 °C and after 30 days at 30 °C. PS-enriched samples presented higher values of hydroperoxides than control samples, which could be attributed to the higher level of alpha-linolenic acid present in the PHYT samples. All chocolate bars became lighter and softer after 90 days of storage. However, these physical changes did not reduce their sensory acceptability. In addition, PS bioactivity was kept during the storage, since no significant alterations in the PS esters were observed up to 5 months. However, some PS oxidation occurred in the PHYT bars, being sitostanetriol, 6-ketositosterol, 6β-hydroxycampesterol and 7-ketocampesterol the major phytosterol oxidation products (POPs). The POPs/PS ratio was low (0.001). Therefore, the dark chocolate bars developed in this study kept their potential functionality after 5 months of storage at room temperature, representing an option as a functional food.     

植物甾醇的研究进展概述

植物甾醇是一类具有较强的生理活性和表面活性的物质,广泛地运用于医药、食品、化妆品、光学产品、饲料、化工、纺织等各个领域。本文简要介绍了植物甾醇的理化性质和生物活性及其应用,综述了近年来植物甾醇研究进展,探讨了其今后的发展方向,旨在为植物甾醇的开发利用提供参考。     

Lipids and phytosterol oxidation products in commercial potato crisps commonly consumed in Sweden

The stability of frying oils and fried foods is mainly affected by the fatty acids present and by the types and levels of minor components such as phytosterols and tocopherols. This study assessed the current status of lipid composition and the occurrence of oxidised phytosterols as a parameter of lipid oxidation in potato crisps available in the Swedish market. Fatty acid composition and concentrations of tocopherols, sterols and phytosterol oxidation products (POPs) were determined in 16 commercial potato crisp samples of two types, distinguished by a high or low fat content. The fatty acid composition in most samples was dominated by saturated and monounsaturated fatty acids. The sum of α-tocopherol and γ-tocopherol content varied from undetectable levels to 10.2 mg/100 g potato crisps, with α-tocopherol dominating. Among the tocotrienols, α-tocotrienol and γ-tocotrienol were present in almost equal proportions, while δ-tocotrienol was present in all samples but in smaller amounts. Fatty acid composition, tocopherol and tocotrienol content, showed that all potato crisp samples were prepared in palm oil or a blend of palm oil and unspecified fats and oils. Total sterol content ranged from 10.2 to 93.1 mg/100 g sample, with β-sitosterol being the major sterol in all samples. The content of POPs ranged from 0.05 to 0.68 mg/100 g potato crisps. In general, there were no significant differences in content of POPs between high and low fat samples, and generally no correlations could be established between content of POPs and fatty acid, tocopherol, tocotrienol, and sterol content among the potato crisp samples.     

植物甾醇和植物甾烷醇:来源、安全性以及在保健食品中的应用

包括植物甾醇和植物甾烷醇在内的植物固醇天然存在于植物细胞中,作为构成细胞膜的组成成分。在植物油和松科树木的树油中含有丰富的植物固醇,特别是β-谷甾醇、菜油甾醇和豆甾醇。在动物实验和人体临床实验中发现植物固醇具有降低总胆固醇和LDL胆固醇的作用。临床实验的结果表明,每日摄入1—2g的植物固醇可以达到降低州10％—15％的血清胆固醇的作用。其作用机制与植物固醇同胆固醇的结构类似性及其在乳糜微粒中的溶解度有关,从而降低胆固醇在肠道中的吸收。一般认为植物固醇是安全的,它本身是正常膳食中的一部份。临床毒理学研究发现有效剂量之内的植物固醇不仅能降低胆固醇而且对人和动物没有毒性,虽然有对于食物中的植物固醇影响类胡萝卜素吸收的担心,但从临床研究的结果中证明只要在膳食中增加一份的富含类胡萝卜素的水果和蔬菜就可以轻易解决这一问题。     

基因食品的营养安全问题

随着生物技术的发展,基因食品逐渐走进我们的生活。本文概述的基因食品的概念,探讨了国内外倍受关注的转基因食品营养及安全问题,详细阐述了转基因食品的功能及其营养,安全问题的解决方法。最后对转基因食品的发展前景进行了展望。     

Inhibition of cholesterol oxidation in marinated foods as affected by antioxidants during heating

Chinese marinated foods rich in cholesterol, such as eggs and pork, can be susceptible to formation of carcinogenic cholesterol oxidation products (COPs) during prolonged heating. The objectives of this study were to compare the effects of various antioxidants on the inhibition of COPs in marinated eggs, pork and juice. The various COPs in marinated food samples were analyzed by a GC–MS technique. The incorporation of antioxidants, vitamin C, vitamin E, BHA and trolox were all effective in inhibiting COPs formation, with vitamin C being the most pronounced in marinated eggs, and BHA in marinated pork and juice. The inhibition effect increased with increasing levels of BHA and trolox. However, vitamin E was more effective at a low level (0.02%) than at a high level (0.1%), probably because of prooxidant activity of the latter. The same phenomenon also occurred for 0.1% vitamin C in marinated eggs, but a reversed trend was observed in marinated pork and juice. The residual amounts of each antioxidant in marinated eggs, pork and juice were also determined by HPLC.     

Risk assessment of Belgian adults for furan contamination through the food chain

Risk assessment is an interdisciplinary process used to quantify the risk linked to a hazard. In the present paper it is applied to quantify the risk linked to furan ingestion through the food chain for the Belgian adult population. Two approaches, deterministic and probabilistic, were carried out in parallel. The deterministic method relied on a case study, whereas the probabilistic approach involved statistical distributions of contamination and consumption data to calculate a statistical distribution of the daily intake. First, the deterministic method revealed a low estimated daily intake (EDI) for the average population (380?ng*(kg_bw*day)^–1) and a huge contribution of coffee consumption to the EDI (55%). Increasing or decreasing the daily coffee consumption by one cup can affect the EDI by about 22%. Afterwards, the probabilistic approach showed that the average population has a low EDI (494?ng*(kg_bw*day)^?1), and that high contamination levels were only registered in a small proportion of the population. Finally, a comparison of the RfD_{chronic oral} showed that less than 10% of the Belgian population had an EDI above the reference dose proposed by the USEPA; the majority of the population had an EDI 20% below the reference dose. The margin of exposure (MoE) approach indicated that the level of risk related to furan intake through ingestion is low, with a MoE?>?10,000 for more than 10% of the population and no result?<?100.     

Antioxidant assessment of an anthocyanin-enriched blackberry extract

Gel filtration of black berry (Rubus fruticosus sp) ethanolic extracts was employed to obtain an anthocyanin-enriched extract. The anthocyanin profile identified cyanidin-3-glucoside as the primary (e.g., 90% of total) anthocyanin present in blackberry. Gel filtration of crude extracts resulted in a 20-fold increase in total anthocyanin content, with no change in the proportion of cyanidin-3-glucoside. Antioxidant activities of both the crude and anthocyanin-enriched blackberry extracts were determined using cell-free (ORAC) and cell-based (INT-407 intracellular) antioxidant assays. Antioxidant activity, assessed by the ORAC assay, indicated a 7-fold increase in activity for the anthocyanin-enriched fraction. Similar results were obtained for the anthocyanin-enriched extract using the intracellular antioxidant assay with INT-407 cells. Our results indicate that the anthocyanin content, and more specifically the presence of cyanidin-3-glucoside, in blackberry, contributes a major part of the antioxidant ability to suppress both peroxyl radical-induced chemical and intracellular oxidation.     

食品中不同铁强化措施的安全性研究

目的研究不同食品强化措施对人群铁摄入水平的影响,为食品强化标准的制修订提供参考。方法基于风险评估基本原则,利用2002年中国居民营养与健康状况调查数据,按年龄、性别、经济发展水平等分层计算模拟实施3种不同的强化措施(强化酱油、强化面粉及酱油面粉同时强化)前后居民的铁摄入水平。结果在全人群水平上,模拟场景下的酱油强化使各组人群中达到适宜摄入量(AI值)的人群比例增加了3%～10%,超出可耐受最高摄入量(UL)的人群比例基本没有增加。面粉强化则使达到AI值的人群比例增加了4%～22%,同时5%左右的2～10岁组人群超出UL。大城市强化前后铁摄入水平变化趋势与全人群基本相同;三类农村地区面粉强化使得2～10岁组、男性18～49岁组人群铁摄入超出UL的比例增加了近20%。结论以铁的最大强化量(27.3mg/100ml)进行的模拟全民酱油铁强化,在改善人群铁缺乏状况的同时能够保证绝大多数居民的食用安全性,因此标准中的现有规定是安全的。以铁的最大强化量(4.8mg/100g)进行的模拟全民面粉强化,可以普遍提高居民铁摄入水平,但也使某些地区的相当部分人群的铁摄入量超过了UL,而2.6mg/100g的铁强化水平相对安全。建议食品强化标准的制定应充分考虑不同地区、不同人群的膳食结构和营养摄入状况。     

Intake and risk assessment of nitrate and nitrite from New Zealand foods and drinking water

Exposure to excess nitrite is a potential health risk for humans. One hundred meat and processed foods and 100 vegetable samples purchased from New Zealand retail outlets were prepared as for consumption and analysed for nitrite and nitrate concentration using a standard, validated methodology. Nitrate concentrations ranged from less than the limit of detection (LOD = 5 mg kg^-1) in cheddar cheese and cream cheese-based dips to 3420 mg kg^-1 in lettuce. Nitrite was detected in half the processed foods and meats analysed (levels up to 119 mg kg^-1), but detected in only one vegetable sample above the LOD (broccoli at 27 mg kg^-1 nitrite). Concentration data were combined with 24 h dietary recall information to generate 4398 individual adult daily exposure scenarios for exogenous nitrite and nitrate including a contribution from water assessed from 1021 drinking water samples. The mean adult daily intake of exogenous nitrate and nitrite from food and water combined was 16 and 13% of the Acceptable Daily Intake (ADI), respectively, and therefore should not pose a health risk for the average consumer. A maximally exposed New Zealand adult is estimated to have an intake of up to seven times the ADI for nitrate. When the endogenous conversion of nitrate to nitrite is taken into account, approximately 10% of people with an average rate of conversion and half of all people with a high rate of conversion are estimated to exceed the ADI. Either the ADI is inappropriate and needs to be re-evaluated, or those individuals who have a high rate of conversion of nitrate to nitrite are at risk to adverse effects of nitrite exposure.     

Use of Volatiles as Indicators of Lipid Oxidation in Muscle Foods

Lipid oxidation has long been recognized as a leading cause of quality deterioration in muscle foods and is often the decisive factor in determining food product storage life. Lipid oxidation generates a number of products, including volatile compounds, which are the major contributors to the development of rancid off‐flavors and odors. Over the years, methodologies have been developed to quantify lipid oxidation products in muscle foods. This article reviews the analytical methods that have been used to quantify volatile compounds as indicators of lipid oxidation in muscle foods. The sampling methodologies of distillation/solvent extraction and headspace analysis, and isolation methods associated with gas chromatographic (GC) and high‐performance liquid chromatography (HPLC) analyses are discussed. Within gas chromatographic methodologies, headspace (HS) sampling (static HS, dynamic purge‐and‐trap HS techniques, and solid‐phase microextraction [SPME]) are addressed.     

乳化食品中油脂氧化分析及其货架期评价方法的研究进展

油脂氧化是导致乳化食品变质的主要原因。油脂中的不饱和脂肪酸发生氧化,不仅会降低乳化食品的营养价值,还会产生不良风味、有害成分,进而影响乳化食品货架期和食用安全。相对于纯油体系,以乳化形式存在的油脂在高油-水界面比下极易发生氧化,缩短乳化食品的货架期。为明确乳化食品中油脂氧化分析以及其货架期评价方法,在介绍乳化食品中油脂氧化的基本过程的基础上,综述了乳化食品中油脂氧化分析方法(过氧化值、共轭二烯值、硫代巴比妥酸值、茴香胺值、挥发性物质含量)以及货架期的评价方法,为乳化食品中油脂氧化程度分析及其货架期预测提供参考。