## 1 Introduction  
Honeydew honey is a type of honey which bees (_Apis mellifera_) produce from excretions of plant-sucking insects or secretions of plants. Thus, the composition of honeydew is dependent on both plant and aphid species, and may also be influenced by environmental factors including water stress and temperature [1, 2]. Two varieties of honeydew honey are distinguished: deciduous honeydew honey andiferous honeydew honey, which in Poland is mainly produced from _Abies alba_. This species occurs mainly in southern and south-eastern Poland. Podkarpackie, an ecologically clean region in south-eastern Poland, is a natural basin of coniferous forests with a predominance of fir trees; therefore, it has a huge potential for the production of honeydew honey. Podkarpackie honeydew honey was registered by the European Commission as a Protected Designation of Origin (PDO) in 2010 [3]. This label was established by the EC to protect the designations of origin of traditional regional food products. Podkarpackie honeydew honey is characterized by a high content of macro- and microelements such as potassium, calcium, magnesium, manganese, copper, iron, and others [4, 5]. This characteristic also results from its geographical origin because Podkarpackie's soil is rich in mineral salts [6]. The characteristic dark color of Podkarpackie honeydew honey results from the species of fir trees (_Abies alba_) found in the described area [5]. Moreover, this Polish honeydew honey is characterized by a higher than standard content of simple sugars, which, combined with its moderate acidity, improves the flavor bouquet of the honey and reduces the sweet taste [7]. The increased interest in honeydew honey is due to its nutritional, sensory, and, therefore, medicinal properties, which are different from flower honey. Considering the organoleptic properties honey is distinguished by its dark color, which in pure fir honey becomes greenish, and specific sensory characteristics such as a delicate resin aroma [7]. Compared to nectar honey, honeydew honey is characterized by higher pH values, electrical conductivity, net absorbance, and ash content; a higher content of disaccharides and trisaccharides; and lower levels of monosaccharides [5; 8]. Actually, according to the applicable standards, a special parameter that distinguishes honeydew honey is its electrical conductivity: for this variety of honey the minimum required is 0.8 mS/cm, while for all nectar honeys it is below the mentioned value [9]. However, researchers are still working on chemical markers of honeydew honey. The presence of melezitose was considered a characteristic feature of honeydew honey, and usually the level of this sugar may indicate what part of a given honey sample was produced from honeydew (also with regard to nectar-honeydew honey) [5; 8]. It is known that a specific feature of honeydew honey is its positive specific rotation assessed polarimetrically, in contrast to nectar honeys [10]. Another marker of honeydew honey often analyzed by scientists is the polyphenol profile; however, the results have not been consistent. Among the proposed polyphenic markers, protocatechic acid (3\(\mathcal{A}\)-dihydroxybenzoic acid), specific for honeydew honey, is commonly determined [11; 12]. Other authors state that the most frequently recurrent polyphenols determined in honeydew honeys are protocatechic, p-hydroxybenzoic acid, caffe acid, p-coumaric acid, ferulic acid, and vanillic acid, as well as the flavonoids chrysin and pinochemrin, which were also proposed to be honeydew honey markers [13; 14]. In addition to polyphenols, which are considered to be the main bioactive ingredients, honeydew honey is characterized by a higher content of minerals, proteins, organic acids, enzymes, amino acids, and vitamins, which are also responsible for the antibacterial and antioxidant activity [5; 7; 8; 15; 16; 17; 18].