1. Introduction

Tualang honey is tropical rainforest honeys that mostly originated from Malaysia. The health benefits of these honeys have recently been gaining increased attention and popularity, as evidenced by numerous documented studies.  This honey possesses anti-microbial, anti-cancer, antioxidant, and anti-inflammatory effects attributed to its high antioxidant contents [6,7]. 

2. Physicochemical Characteristics

These honeys have unique physicochemical properties mostly attributed to Malaysia’s tropical climate.  Table 1;  Table 2 show the physicochemical characterisation of Tualang honey extracted from various studies.

On the one hand, Tualang honey mostly complied with the accepted range by the two most common legislation of honey criteria and standards referred to as the European Honey Legislation [12] and Codex Alimentarius Standards for Honey [13]. According to the European Honey Legislation and the Codex Alimentarius Standards, honey moisture should be less than 20%, with glucose and fructose composition of more than 60 g/100 g, sucrose content of not more than 5 g/100 g and electrical conductivity of not more than 0.8 mS/cm. 

Most of the studies reported that Tualang honey contained more than 20% moisture content, thus violating European Honey Legislation and Codex Alimentarius Standards. Nonetheless, honey samples from tropical countries, such as Malaysia, typically have higher moisture content, which could be due to the rainy season all over the year [15]. Therefore, Malaysia’s honey is always first treated by evaporation to reduce the water content, thereby simultaneously increasing the honey quality [16].

Meanwhile, the electrical conductivity of honey is used to determine the botanical origin and purity of honey [17]. An electrical conductivity of less than 0.8 mS/cm indicates blossom honey, whilst more than 0.8 mS/cm indicates honeydew honey [18]. According to the European Honey Legislation and the Codex Alimentarius Standards, honey’s electrical conductivity should not be more than 0.8 mS/cm. The electrical conductivity of Tualang honey is in a broad range of 0.74–1.51 mS/cm. Various factors, such as storage, time, temperature, water content and concentration of ions and minerals, were reported to contribute to the electrical conductivity of honey [16].

Most bacteria grow in a neutral and mildly alkaline environment, whereas yeasts and moulds could grow in an acidic environment (pH = 4.0–4.5). Conversely, the pH values of honey are neither those needed for bacteria nor yeast growth [15]. This is of great importance during storage, as they influence the texture, stability and shelf-life of honey [18]. The pH value of Tualang honey were reported to be in the range of 3.14–3.83. Moreover, the sugar content has complied with the requirement of the European Honey Legislation and Codex Alimentarius Standards. In terms of honey colour characteristics, Tualang honey is described as light amber honey [15,19].

Many studies found that the antioxidant capacity of honey is strongly correlated with the concentration of its phenolic contents [20,21]. The phenolic content of honey comes from the plant that the bees feed on [22]. Thus, botanical origin plays a significant role in determining the constituents and antioxidant activity of honey [23]. Colour intensity is also associated with antioxidant properties. Numerous studies, including those on Gelam honey, associated the honey colour intensity with antioxidant properties. Darker-coloured honey showed higher antioxidant activity and higher total phenolic content [22,24–26]. The present review also found that the honey have a high content of phenolic and flavonoid.

The determination of trace elements in honey is essential for quality control and monitoring of trace element composition. High levels of trace elements could be dangerous and cause toxicity. The levels of trace elements in Tualang honey was within the permissible value set by the World Health Organization (WHO), and no honey contamination with pesticide residues was found [28].

Table 1. Physicochemical characteristics of Tualang honey.

Table 2. Chemical constituents of Tualang honey.

3. Medicinal Properties

Tualang honey shared these major health benefits; (a) anti-oxidative; (b) anti-cancer; (c) anti-inflammatory; (d) wound-healing; (e) anti-microbial; (f) anti-diabetic and; (g) anti-obesity (as seen in Figure 1).

Figure 1. The medicinal properties of Tualang, Gelam and Kelulut honeys. ROS: reactive oxygen species; MDA: malondialdehyde; SOD: superoxide dismutase; CAT: catalase; GPX: glutathione peroxidase; TGFβ: transforming growth factor beta; Apaf-1: Apoptotic protease activating factor-1; IFN‐γ: interferon‐gamma; IFNGR1: interferon gamma receptor-1; p53: tumor protein P53; ESR1: oestrogen receptor-1; TNF-α: tumor necrosis factor alpha; Bcl-xL: B-cell lymphoma-extra-large; IL-1β: interleukin-1 beta; IL-6: interleukin 6; IL-8: interleukin 8; IL-10: interleukin 10; NF-kB: nuclear factor kappa B; IκBα: NF-kappa-B inhibitor alpha; COX-2: cyclooxygenase-2.

This entry is adapted from the peer-reviewed paper 10.3390/nu13010197