Effect of Microwave Treatment on Microbial Contamination of Honeys and in Their Physicochemical and Thermal Properties

Abstract

In recent years, microwave heating has become a common method for pasteurization and sterilization of food. Honey is a sweet substance produced by worker honeybees from nectar of fl owers. The major microbial contaminants include moulds and yeasts, as well as the spore-forming bacteria, being their counts indicative of honeys' commercial quality and safety. Paenibacillus larvae is also of interest since it causes American foulbrood (AFB) in honeybee larvae. The main quality factors that are used in the honey international trade are moisture, hydroxymethylfurfural content (HMF), and enzymatic indices. Moreover, honey exhibits several thermal events, the most important being the glass transition temperature (Tg). The aim of this work was to evaluate microwave effect (800 watts during 45 and 90 seconds) on microbial content in particular over P. larvae spores retained in honey, and on physicochemical and thermal properties. Microwave promoted a decrease of microbial count with time of exposure, including P. larvae. Moisture content diminished after treatment, while Tg increased linearly, and acidity decremented in the majority of cases. Honeys darkened and HMF exceeded the permissible value. Diastase and glucose-oxidase enzymes were totally inactivated by microwave treatment.Unauthenticated Download Date | 5/8/18 7:10 AM

The Influence of Preventing Crystallization Treatment on the Selected Quality Parameters of Honey

“…Such a result in relation to honey could be expected because of the heat effect of the treatments applied. Similar observations were made by other researchers, testing heating with air, microwaves and sonication [21,14,16,23]. The proportion of water in honey increased only with long and sequential heating of honey with air having a temperature of 45 °C.…”

“…Water and HMF contents in the samples subjected to the treatment to prevent crystallization by heating, exposure to microwaves and sonication, are shown in Table 2. The moisture of honey depends on many factors, such as the harvesting season, a degree of maturity, climatic factors and a post-harvest treatment [16]. An increase or loss in product moisture after exposure to air depends on the temperature, moisture and relative humidity of air [14].…”

Conventional and emergent technologies for honey processing: A perspective on microbiological safety, bioactivity, and quality

“…An additional effect of microwave heating seems to be the loss of antimicrobial activity, mainly due to the inactivation of enzymes, such as glucose oxidase, which play a significant role in honey's antimicrobial activity (Bucekova, Juricova, Monton, et al, 2018;Moline et al, 2015). Other effects of microwave heating are summarized in Table 5.…”

Microbiological Quality of Polish Artisanal Varietal Honeys

“…Another biological threat found in honey is microorganisms that produce spores resistant to adverse environmental conditions. Among them, Gram-positive anaerobic spore-producing Clostridium , aerobic spore-producing bacilli and moulds are detected [ 11 , 12 ]. Spores can survive in honey for a long time, withstanding ambient (environmental) temperatures and thermal processes.…”

“…It is generally accepted that a small number of low-diversity microbiota are present in honey [ 14 ]. The phenomenon of spores not converting to vegetative forms and remaining alive in honey indicates its inhibitory role against microorganisms [ 4 , 12 ].…”