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Received Jan 19, 2018; Revised Mar 29, 2018; Accepted Apr 3, 2018
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
Coffee has been a major economic plant in Thailand for a long time. Thailand is the third largest producer of coffee in Asia. The most widely cultivated species is Coffea canephora or robusta, which accounts for 99% of coffee production in Thailand [1]. Conditions in the south of Thailand are perfect for growth, such as Chumphon, Nakhrn Si Thammarat, Yala, and Krabi provinces. Geography has a strong effect on the characteristics and physiological properties of coffee beans, such as flavors, quality, and chemical content [2]. Despite the lower quality of robusta coffee beans, it is popular as instant coffee in the beverage industry [3]. Green coffee beans contain polyphenol compounds, such as chlorogenic acid and its related compounds (caffeic acid, ferulic acid, and coumaric acid) which are used to inhibit the oxidative stress [4]. Phenolic compounds have attracted interest because of their antioxidant potential and anti-inflammatory activity [5, 6]. According to a previous scientific study, green coffee beans contain a higher amount of chlorogenic acid than roasted coffee beans and other plants [7]. Our preliminary study found that the green robusta coffee beans extract contained phenolic compounds that were unstable under light and temperature. The antioxidant activities of the extract declined at high temperature after a period of storage. These problems affected the stability of phenolic compounds, and thus nanostructured lipid carriers (NLCs) were selected to reduce this problem.
Nanotechnology involves the synthesis of nanoparticles with a particle size ranging from 20 to 200 nm having been applied in food, pharmaceutical, and cosmetic industries. Several lipid nanoparticles including liposomes, nanoemulsions, and solid lipid nanoparticles (SLNs) have been studied for decades. Liposomes can contain lipophilic drugs and hydrophilic drugs. However, they have many disadvantages including low drug loading, drug leakage, and fast release [8]. Nanoemulsions are optically transparent or slightly opaque emulsion with a small droplet size. Nanoemulsions are unstable due to Ostwald ripening, and controlled drug release is improbable due to their small particle size. SLNs are the first generation of lipid...