1、PDF外文：http:/ 1 页 中文 6900 字 出处： Journal of Food Engineering, 2010, 96(4): 533-539. 原 文 题目： Concentration of avonoids and phenolic compounds in aqueous and ethanolicpropolis extracts through nanoltration Abstract Propolis has a variable and complex chem
2、ical composition with high concentration of avonoids andphenolic compounds present in the extract. The extract varies with the solvent used in extraction. Ethanol extracts more phenolic acid and polar compounds than water. Before their use in industry, extracts must be concentrated but the use of hi
3、gh temperatures can degrade some compounds. Membrane pro-cesses is an option that allows concentration at low temperatures. Nanoltration was carried out withaqueous and ethanolic extracts and each extract results in two distinct fractions: permeate and retentate. The capacity of the membrane to reta
4、in the compounds was veried by spectrophotometric analysis: for aqueous solution, the membrane retained around 94% of the phenolic compounds and 99% of the avonoids, while for the ethanolic solution these values were 53% and 90%, respectively. Ferulic acid retentionindex was 1.00 and 0.88 to aqueous
5、 and ethanolic solutions, respectively. Thus, the nanoltration processshowed high efciency in the concentration of propolis extracts. 1 Introduction Over the last few decades, interest in functional foods has beengrowing fast, leading to the discovery of new functional components or processes that c
6、an improve food processing, as well as products that may help to retard aging or avoid diseases. In this context, bee products have gained the attention of consumers and researchers, due to their chemical compositions and functional properties. Propolis is one of the bee products with functional pro
7、perties, but it cannot be consumed as a food because it is a resinous substance. It is prepared from the buds and exudates of certain trees and plants. These substances are transformed by the addition of wax and the enzyme glucosidase present in the bee saliva in order to form propolis (Bankova et a
8、l., 2000； Park et al., 1998). The product obtained is used by honeybees to protect the hives against invaders and contamination, to seal holes and 第 2 页 to maintain the temperature. Some important characteristics have been reported for this substance, such as anti-microbial and antioxida
9、nt effects, anesthetic properties and others. Due to these characteristics, which can bring health benets, propolis is considered a functional ingredient and is used in food, beverages, cosmetics and medicine to improve health and prevent diseases (Burdock, 1998； IFIC, 2009). There are over 150 cons
10、tituents in propolis, including polyphenols, terpenoids, steroids and amino acids. Flavonoids are one of the most important groups and can represent around 50% of the propolis contents,depending on the region where it is collected, since its characteristics is inuenced by plants and weather (Krell,
11、1996； Park et al., 1998). Kumazawa et al. (2004) tested the antioxidant activity of propolis from various geographic origins and showed different activities for each sample. Other studies indicated that the propolis from Europe and China contained many kinds of avonoids and phenolic acids, whereas t
12、he Brazilian samples had more terpenoids and prenylated derivatives of p-cumaric acid (Bankova et al., 2000). Finally, each combination of compounds in the propolis of acertain origin can represent specic characteristics in the nal product. The most common propolis extracting process uses ethanol as
13、 the solvent. However, this has some disadvantages such as the strong residual avor, adverse reactions and intolerance to alcohol of some people (Konishi et al., 2004). Researchers and industry are interested in producing a new type of extract with the same compounds extracted by the ethanolic metho
14、d, but without the disadvantages. Water has been tested as the solvent, but resulted in a product containing less extracted compounds (Park et al., 1998). Konishi et al. (2004) tested water with a combination of some tensoactive compounds to replace part of the alcohol used in propolis extraction an
15、d all the tests were efcient in extracting it, and the product showed good anti-microbial activity. Depending on the application, the solvent in propolis extracts must be reduced or eliminated. The processes that are used today, as lyophilization, vacuum distillation and evaporation, have some disad
16、vantages like the use of high temperatures and high energy consumption. Lyophilization requires large amounts of energy, since the sample needs to be maintained at 20 C for at least 24 h, and energy is also required for the sublimation of the solvent used during preparation of the extract. Moreover,
17、 the method often requires a previous stage of concentration, maintaining the product at 70 C until part of the solvent is 第 3 页 evaporated. Vacuum distillation requires great amounts of energy to generate the vacuum, and can lead to loss of compounds of low molecular weight, which can b
18、e removed together with the solvent evaporated in the system. Evaporation maintains the extract underheating at 70 C, until all the solvent is removed. This process, in addition to the high demand for energy, can degrade the avonoid and phenolic compounds in propolis, due to the temperature used. Ho
19、wever, it is the process that gives greater ease of implementation in companies due to low cost on the equipment required compared with the previous cases. The use of membrane concentration processes has been growing due to certain advantages, such as: low temperatures, absence of phase transition a
20、nd low energy consumption (Matta et al., 2004). This procedure is based on the principle of selective permeation of the solute molecules through semi-permeable, polymeric or inorganic membranes. The driving force for mass transfer across the membrane in most membrane processes, such as a microltrati
21、on, ultraltration, nanoltration and reverse osmosis is mechanical pressure (Maroulis and Saravacos, 2003). Nanoltration is a unit operation that permits many applications, such as solvent recovery from ltered oil, exchange of solvents in the chemical industry (Geens et al., 2006), concentration and
22、purication of ethanolic extracts of xantophylls, which is important in both the pharmaceutical and food industries (Tsui and Cheryan, 2007) and in wine concentration (Banvolgyi et al., 2006), as well as in juice concentration (Vincze et al., 2006) in the food industry. The objective of this study wa
23、s to investigate the membrane concentration of propolis extracts using water and ethanol as the solvents, exclusively, verifying the quality of the concentrated products in terms of the retention of avonoids and phenolic compounds during processing. The process was evaluated according to the permeat
24、e ux, inuence of temperature and pressure and concentration factor. The results obtained for each solution were compared to verify the viability of developing a new propolis product, based on water as the solvent. 2. Materials and methods 2.1. Propolis Raw propolis was obtained from Apis mellifera beehives in the State of So Paulo, Brazil, and was acquired in a single batch, in order to minimize the variability associated
