Study on Power Ultrasound Optimization and Its Comparison with Conventional Thermal Processing for Treatment of Raw Honey

Svrha je ovog rada bila optimirati postupak obrade ultrazvukom visokog intenziteta pomoću metodologije odzivnih površina i postići maksimalnu aktivnost dijastaze i minimalni udjel hidroksimetilfurfurala u medu. Proveden je eksperimentalni dizajn s različitim trajanjem obrade (1 do 15 min), amplitudom (20 do 100 %) i volumenom (40 do 80 mL) kao nezavisnim varijablama pri kontroliranoj temperaturi, te je zaključeno da se optimalna aktivnost dijastaze od 32,07 Schade jedinica i udjel hidroksimetilfurfurala od 30,14 mg/kg postižu nakon 8 min obrade, uz amplitudu od 60 % i volumen od 60 mL. Daljnja ispitivanja temperaturnog profila obavljena su na početnim temperaturama od 65, 75, 85 i 95 °C do postizanja konačne temperature uzoraka od 65 °C, nakon čega je temperatura održavana konstantnom tijekom 25 min. Rezultati su uspoređeni s onima dobivenim optimiranom obradom ultrazvukom visokog intenziteta. Ultrazvučna obrada najmanje je utjecala na značajke kakvoće, poput udjela vlage, pH-vrijednosti, aktivnosti dijastaze, udjela hidroksimetilfurfurala, karakteristike boje i ukupne razlike u boji meda. Također, mikrobiološkom je analizom potvrđeno da je med obrađen ultrazvukom visokog intenziteta imao manji ukupni broj aerobnih mezofilnih i koliformnih bakterija, te kvasaca i plijesni od toplinski obrađenog meda. Stoga je zaključeno da se obrada ultrazvukom visokog intenziteta pri navedenim uvjetima može primijeniti kao alternativni netermalni postupak obrade meda.
The present study was done to optimize the power ultrasound processing for maximizing diastase activity of and minimizing hydroxymethylfurfural (HMF) content in honey using response surface methodology. Experimental design with treatment time (1-15 min), amplitude (20-100 %) and volume (40-80 mL) as independent variables under controlled temperature conditions was studied and it was concluded that treatment time of 8 min, amplitude of 60 % and volume of 60 mL give optimal diastase activity and HMF content, i.e. 32.07 Schade units and 30.14 mg/kg, respectively. Further thermal profile analyses were done with initial heating temperatures of 65, 75, 85 and 95 ºC until temperature of honey reached up to 65 ºC followed by holding time of 25 min at 65 ºC, and the results were compared with thermal profile of honey treated with optimized power ultrasound. The quality characteristics like moisture, pH, diastase activity, HMF content, colour parameters and total colour difference were least affected by optimized power ultrasound treatment. Microbiological analysis also showed lower counts of aerobic mesophilic bacteria and in ultrasonically treated honey than in thermally processed honey samples complete destruction of coliforms, yeasts and moulds. Thus, it was concluded that power ultrasound under suggested operating conditions is an alternative nonthermal processing technique for honey.