# A Comprehensive Review of Stingless Bee Products:
## 2 Stingless Bee Honey  
Stingless bees are a highly eusocial insect, and similar to European honeybees, stingless bees produce and store honey in their hives. However, the amount of honey stored in the hive of a stingless bee is less than that of European honeybees [11]. Honey stored by stingless bees is fivefold less than that of European honeybees, with the average production per colony of stingless bee honey only up to 1 kg, compared to European honeybee honey, which can be up to 5 kg per colony [12]. In general, the quality parameters used to evaluate stingless bee honey include moisture content, pH, free acidity, organic acids, and 5-hydroxymethylfurfural [13]. Unlike European honeybee honey, which has International Honey Commission (IHC) standards to monitor the honey quality [14], the international standard for quality control of stingless bee honey has not yet been established. [PERSON] et al. [15] proposed that stingless bee honey quality should have a moisture content maximum value of 30 g/100 g, sum of fructose and glucose minimum value of 50 g/100 g, sucrose content maximum value of 6 g/100 g, free acidity maximum value of 85 meq/kg, ash content maximum value of  
Figure 1: Mustafa-Hive system used by Malaysian farmers. Reprinted with permission from Ref. [10]. 2018, Penerbit Universiti Sains Malaysia. 0.5 g/100 g, hydroxymethylfurfural (HMF) content maximum value of 40 mg/kg, and diastase activity minimum value of 3 diastase number (DN). Recently, the Department of Malaysian Standards [16] published quality standards for Malaysian stingless bee honey to control the supply and sale of stingless bee honey in Malaysia. The department stated that good-quality stingless bee honey should have a moisture content with a maximum value of 35 g/100 g, sum of fructose and glucose maximum value of 85 g/100 g, sucrose content maximum value of 7.5 g/100 g, maltose content maximum value of 9.5 g/100 g, ash content maximum value of 1.0 g/100 g, HMF content maximum value of 30 mg/kg, pH value within 2.5 and 3.8, and natural phenolic compounds to be present without any value limit. Though IHC Standards were not meant for stingless bee honey, a comparison of the proposed standards by [PERSON] et al. [15] and the Malaysian Standards for stingless bee honey is shown in Table 1.  
Stingless bee honey has been reported to have a low pH value, which could be affected by several factors such as storage conditions and the extraction process. Furthermore, the pH itself affects the texture, stability, and shelf life of the honey. In addition, the acidity also gives extra flavour to the honey and is an indicator of microbial stability, as most bacteria cannot grow in an acidic environment [17]. Several reports that comply with the Malaysian Standards are from the species of _Tetragonula fusecobaltate_ ([PERSON], 1908), _Tetragonula hecviceps-pagdeni_ complex, _Tetragonula testacitasis_ ([PERSON], 1901), _Tetrigona melanoucca_ ([PERSON], 1929), _Tetrigona apialis_ ([PERSON], 1857) [11], _Tetrigona laevis_ (18), and _Tetrigona binghami_ ([PERSON], 1937) [19; 20]. Furthermore, the free acidity was not set by the Malaysian Standards but was set by the IHC and [PERSON] et al. [15], in which the maximum free acidity of European honeybee honey is 50 and 85 meg/100 g. Some of the reported stingless bees that comply with both of the standards are _Geniotrigona thoracica_ [21], _Melipona arufivestris_, _Trigona tuscipennis_, _Melipona quadrifusciata_ ([PERSON], 1836), _Melipona murginata_ ([PERSON], 1836), _Melipona montury_ ([PERSON], 1863), _Melipona scutellaris_ ([PERSON], 1811), _Scaptorrigona bipunctata_ ([PERSON], 1836), and _Tetrigonaisca angustula_ ([PERSON], 1811) [9]. Moisture is the second largest component in honey, which is attributed to the botanical origin of nectar, climate, and handling during harvesting. Furthermore, the moisture content is considered an important component in honey, as it could affect the viscosity, specific weight, maturity, flavour, and crystallisation [22].