Abstract
The aim of this study was to evaluate the effect of ultrasound treatment for preventing honey crystallization on the physicochemical and microbiological properties of unifloral honey and polyfloral honey. Honey samples without any treatment were used as a control group for comparison. The effect of applying ultrasound treatment was evaluated by studying over time the tendency of crystallization, the rheological properties of honey and chemical and microbiological properties. The parameters analyzed for the two groups of samples (treated and untreated with ultrasound), which did not vary or had small variations during the research were water content, acidity, water activity, glucose, fructose, sucrose, glucose/water ratio, glucose/fructose ratio. The crystallization process was installed in the control samples from the first month of the study, and much later in the treated samples. The color of the untreated samples varied considerably, and the color of the treated ones remained stable or slightly varied. For the control samples, the smallest variation in hydroxymethylfurfural (HMF) concentration was in raspberry honey (5%), and the most significant variation was in honeydew honey (30%). For the treated samples, the largest variation of this parameter was found in tillia honey (127%), and the smallest variation was in rapeseed honey (26%). The microbiological quality was higher for the treated samples. In the ultrasound-treated samples of acacia honey, honeydew honey and grassland honey, yeasts, molds or standard plate counts (SPCs) were undetectable. For control samples, SPC values were <10–50 cfu/g. Ultrasound-treated samples maintained their SPC parameter levels or were thus reduced (<10–20 cfu/g). Yeasts and molds were undetectable or had value between <10 and 10 cfu/g. The yeasts and the molds ranged in the control samples between <10 and 40 cfu/g.
Highlights
Honey is a natural sweet substance produced by Apis mellifera bees, according to Directive 2001/110 EC [1]
The glucose/water ratio is considered another indicator of honey crystallization [9]
In the treated sample, the diastatic activity varied between 18.1◦ and 16.5◦ Göthe, for raspberry honey it varied between 27.8◦ and 27.1◦ Göthe, in tillia honey between 22.9◦ and 21.8◦ Göthe, in polyfloral honey between 17.8◦ and 16.3◦ Göthe, in rapeseed honey between 17.9◦ and 16.5◦ Göthe, in honeydew honey between 17.5◦ and 16.0◦ Göthe and in grassland honey between 29.0◦ and 24.4◦ Göthe. These results show that the ultrasound treatment application, at a frequency of 42 kHz, has the same effect for all the types of honey subject to our analysis; it acts on diastase, reducing the value of its activity in time
Summary
Honey is a natural sweet substance produced by Apis mellifera bees, according to Directive 2001/110 EC [1]. The chemical composition of honey is characterized mainly by the high percentage of sugars (approximately 80%), glucose and fructose being the main compounds [2]. The ratio of the main sugars, glucose and fructose, is important in the evaluation of the crystallization tendency of honey [5]. Glucose tends to crystallize spontaneously due to its low solubility in water [6]. The glucose/water ratio is considered another indicator of honey crystallization [9]. The value of the glucose/water ratio below 1.7 indicates that the honey crystallizes slowly, and a value higher than 2.0 indicates rapid crystallization [10,11]. The appearance of crystallization in honey is an undesirable process [12] because for consumers this process is a reason to refuse the consumption of the product [13]
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