Lycopene in tomatoes: chemical and physical properties affected by food processing

Lycopene is the pigment principally responsible for the characteristic deep-red color of ripe tomato fruits and tomato products. It has attracted attention due to its biological and physicochemical properties, especially related to its effects as a natural antioxidant. Although it has no provitamin A activity, lycopene does exhibit a physical quenching rate constant with singlet oxygen almost twice as high as that of beta-carotene. This makes its presence in the diet of considerable interest. Increasing clinical evidence supports the role of lycopene as a micronutrient with important health benefits, because it appears to provide protection against a broad range of epithelial cancers. Tomatoes and related tomato products are the major source of lycopene compounds, and are also considered an important source of carotenoids in the human diet. Undesirable degradation of lycopene not only affects the sensory quality of the final products, but also the health benefit of tomato-based foods for the human body. Lycopene in fresh tomato fruits occurs essentially in the all-trans configuration. The main causes of tomato lycopene degradation during processing are isomerization and oxidation. Isomerization converts all-trans isomers to cis-isomers due to additional energy input and results in an unstable, energy-rich station. Determination of the degree of lycopene isomerization during processing would provide a measure of the potential health benefits of tomato-based foods. Thermal processing (bleaching, retorting, and freezing processes) generally cause some loss of lycopene in tomato-based foods. Heat induces isomerization of the all-trans to cis forms. The cis-isomers increase with temperature and processing time. In general, dehydrated and powdered tomatoes have poor lycopene stability unless carefully processed and promptly placed in a hermetically sealed and inert atmosphere for storage. A significant increase in the cis-isomers with a simultaneous decrease in the all-trans isomers can be observed in the dehydrated tomato samples using the different dehydration methods. Frozen foods and heat-sterilized foods exhibit excellent lycopene stability throughout their normal temperature storage shelf life. Lycopene bioavailability (absorption) can be influenced by many factors. The bioavailability of cis-isomers in food is higher than that of all-trans isomers. Lycopene bioavailability in processed tomato products is higher than in unprocessed fresh tomatoes. The composition and structure of the food also have an impact on the bioavailability of lycopene and may affect the release of lycopene from the tomato tissue matrix. Food processing may improve lycopene bioavailability by breaking down cell walls, which weakens the bonding forces between lycopene and tissue matrix, thus making lycopene more accessible and enhancing the cis-isomerization. More information on lycopene bioavailability, however, is needed. The pharmacokinetic properties of lycopene remain particularly poorly understood. Further research on the bioavalability, pharmacology, biochemistry, and physiology must be done to reveal the mechanism of lycopene in human diet, and the in vivo metabolism of lycopene. Consumer demand for healthy food products provides an opportunity to develop lycopene-rich food as new functional foods, as well as food-grade and pharmaceutical-grade lycopene as new nutraceutical products. An industrial scale, environmentally friendly lycopene extraction and purification procedure with minimal loss of bioactivities is highly desirable for the foods, feed, cosmetic, and pharmaceutical industries. High-quality lycopene products that meet food safety regulations will offer potential benefits to the food industry.     

番茄红素热异构化机制及其影响因素研究进展

番茄红素是来自植物性食物中最重要的类胡萝卜素之一,它具有抗氧化、预防前列腺癌和心血管疾病的功 能。生鲜植物性食品中的番茄红素主要为全反式构型,但研究表明全反式番茄红素的生物活性和生物利用率不及其 顺式异构体。因此,利用食品加工技术（光照、加热、氧化、改变pH值、添加表面活性剂）促进食品中番茄红素 的异构化对提升产品营养品质具有重要意义,其中热处理是最方便、最经济的方式。本文在论述番茄红素热异构化 作用机制的基础上,分别对模拟体系和食物体系中的番茄红素热异构化的影响因素（溶剂种类、加热温度、加热时 间等）进行探讨,并得出溶剂种类和食物基质对番茄红素热异构化影响较大,提高温度或延长加热时间可促进番茄 红素异构化甚至使其发生降解的结论。最后提出了该领域研究中存在的问题及今后的研究方向。     

番茄加工新趋势

综述了当今番茄加工的新趋势:采用新方法、新技术生产高质量传统番茄制品,科学合理地从番茄中分离番茄红素,综合利用番茄皮渣,并给我国番茄加工的研究和发展提出一些有用的建议。     

加工方式对两种贝类中8种重金属元素生物可及性的影响

目的 分析水煮和烘烤两种加工方式对两种贝类元素中8种金属元素生物可及性的影响。方法 采用体外模拟消化实验,利用电感耦合等离子体质谱仪(inductively coupled plasma-mass spectrometry, ICP-MS)分析牡蛎(Crassostrea gigas)和扇贝(Azumapecten farreri)体内8种元素(铁、砷、镉、铜、铁、锌、锰、汞)的生物可及性和含量的变化。结果 两种贝类元素含量的趋势大体一致,从高到低依次为锌>铁>铜>镉>砷>铅>汞。两种贝类中生物可及性最高的是牡蛎中的砷元素,为98.4%。生物可及性最低的是扇贝中的铁元素,为3.4%。经过不同的加工方式处理后,能显著提高两种贝类锰元素的生物可及性及显著降低牡蛎中铜、砷、铅元素的生物可及性。加热处理后扇贝中砷和镉元素的生物可及性增加。相较于蒸煮的加热方式,烘烤的加工方式对贝类元素生物可及性的影响更大。通过相关性分析可以看出,贝类元素生物可及性不仅与元素种类、加工方式相关,也与其他元素浓度相关。结论 水煮和烘烤两种加工方式对贝类中8种重金属元素浓度和生物可...     

温度对高顺式占比番茄红素稳定性影响研究

相比全反式,顺式番茄红素异构体具有更高的生物活性和生物利用率,但易氧化降解及向反式构型的回复。作者以YMC Carotenoid C30-HPLC为检测系统研究温度对其稳定性影响。结果表明以乙酸乙酯为介质,热回流-重结晶联用技术制备了顺式异构体占比达78%~85%的番茄红素产品。贮存稳定性试验表明,温度越低,各异构体降解速率常数的绝对值(k)越小,表明其降解越慢、贮藏越稳定。同时模型参数表明,等温条件下,kAll-Ek9-Zk13-Z。9-Z、13-Z、All-E和AllZ异构体在贮藏过程中表现出来的活化能分别为46.42,29.19,56.94,32.45 kJ/mol。所以3种主要番茄红素异构体中,稳定性由高到低依次为:All-E9Z13Z。高顺式占比产品表现出总的活化能为33.76 kJ/mol。     

Lycopene: Isomerization Effects on Bioavailability and Bioactivity Properties

Lycopene cis-isomers have shown to be more bioavailable and bioactive than the naturally occurring all-trans-isomer. During food processing, lycopene undergoes geometrical isomerization, increasing the proportion of cis-isomers. However, lycopene tends to retro-isomerize during food storage. Because the stability, bioavailability, and distribution of lycopene isomers are physiochemical characteristics critical for health benefits, it is essential to preserve these properties in food products containing lycopene isomers.

The objective of this article is to review thermal and nonthermal technologies available for lycopene geometrical isomerization with a focus on the stability, bioavailability, and bioactivity of lycopene isomers.     

热处理对不同颜色番茄中类胡萝卜素异构化和降解的影响

为综合利用彩色番茄资源,对比不同颜色番茄中类胡萝卜素的组成,研究类胡萝卜素热稳定性,阐述其异构化和降解的规律.利用高效液相色谱-二极管阵列检测器(HPLC-PDA)并配备YMC Carotenoid C30色谱柱分离类胡萝 卜素,并以光谱特征鉴定异构体,系统分析番茄中类胡萝卜素组成,并探究热处理温度和时间对其类胡萝卜素...     

超声波湿法提取番茄酱中番茄红素工艺的研究

采用超声波辅助提取工艺，以番茄酱为原料，研究了提取溶剂、原料预处理方式、超声输出功率、提取料液比、提取温度、提取时间等因素对番茄红素提取效果的影响，通过正交实验，确定超声波湿法提取番茄酱中番茄红素的最佳工艺条件为：以乙酸乙酯为提取溶剂，70％乙醇按1：3（w／v）的比例对番茄酱脱水处理3次，超声输出功率160W，料液比1：9（w／v），提取温度40℃，提取时间20min，二级提取，番茄红素提取率为98．7％。所得油树脂番茄红素含量为7．7％。     

4种白藜芦醇蛋白纳米颗粒的生物可及性研究

白藜芦醇的低水溶性和不稳定性等缺点限制了其生物利用度。本文通过探究4种蛋白纳米颗粒的包封性能及体外消化形式,研究其对白藜芦醇生物可及性的影响。结果表明,白藜芦醇与各蛋白主要通过疏水相互作用结合,并以无定形状态包封在颗粒内部。玉米醇溶蛋白纳米颗粒（ZRNP）和酪蛋白酸钠纳米颗粒（CRNP）由于良好的疏水性,包封率在80%以上。在体外模拟消化过程中,ZRNP聚集使白藜芦醇释放率低至（33.95±0.98）%;乳清分离蛋白纳米颗粒（WRNP）具有较强的抗消化能力,导致游离氨基酸释放率仅为（22.84±1.40）%。CRNP和大豆分离蛋白纳米颗粒（SRNP）可以显著提高游离白藜芦醇的体外生物可及性达50%以上。结合包封性能以及体外消化过程中的作用形式,CRNP作为白藜芦醇的包封载体,有望提高其生物可及性。本研究为提高疏水性多酚的生物利用及其在功能性食品上的应用提供理论基础。