Changes in α-amylase activity in honey during the freeze-drying process

A. Keke* and I. Cinkmanis

Latvia University of Life Sciences and Technologies, Faculty of Food Technology, Department of Chemistry, Liela Street 2, LV-3001 Jelgava, Latvia
*Correspondence: anete.keke@llu.lv

Abstract:

Honey is a natural product, which is appreciated for its sweetness, high nutritional value and health benefits all over the world. Despite all benefits, the usage of honey in food industry is limited due to its high viscosity. The use of dried honey could be an alternative to liquid honey, and would allow to use it as an additive in a range of many different food products such as sauces, beverages, yogurts etc. There are many parameters, which are used to determinate the quality of honey. α-amylase (diastase) activity is one of the most important criteria to determine the quality and freshness of honey. The aim of the present study was to investigate and compare α-amylase activity in liquid honey samples and freeze-dried honey samples. Overall, 18 honey samples were dehydrated using a freeze-drying method. Freeze-drying of the samples was carried out at – 50.6 °C and the pressure was 0.036 mbar for 72 hours. α-amylase activity in the honey samples was tested using Amylazyme test tablets. The obtained results showed variability in α-amylase activity after the freeze-drying process. As hydroxymethylfurfural (HMF) is another important quality parameter of honey, the content of HMF was determined in the samples by high performance liquid chromatography. In some samples the concentration of HMF after freeze-drying increased and was higher than it is allowed according to the International Honey Commission (for example, 55.75 mg kg^-1).

Key words:

Developing a household vacuum cooking equipment, testing its performance on strawberry jam production and its comparison with atmospheric cooking

D. Tomruk¹, E. Devseren¹, M. Koç², Ö.Ö. Ocak¹, H. Karataş³ and F. Kaymak-Ertekin¹*

¹Ege University, Faculty of Engineering, Food Engineering Department, TR 35100 Bornova-İzmir, Turkey
²Adnan Menderes University, Faculty of Engineering, Food Engineering Department, TR 09010 Aydın, Turkey
³Arçelik A. Ş., R&D Center, TR 34940 İstanbul, Turkey
*Correspondence: figen.ertekin@ege.edu.tr

Abstract:

In this research, the performance of a kitchen appliance cooking equipment prototype, which can operate either under vacuum or at atmospheric pressure, is aimed to be developed and tested on strawberry jam production. Vacuum cooking applications were carried out at two different conditions as 17.5 and 25 minutes at 75 °C. Strawberry jam was also cooked at atmospheric pressure for 5, 10, 15 and 20 min. The effect of cooking conditions under vacuum and atmospheric pressure was determined by the following analysis; brix, color (L*, a*, b*) values, chroma (C*), hue (h°), pH value, titratable acidity, reducing and total sugar content (%), hydroxymethylfurfural content (HMF) and sensorial analysis. When the strawberry jam that is produced at atmospheric pressure is compared to the ones that are produced under vacuum, atmospheric cooked jam got higher Brix and was more viscous depending on the applied elevated temperature. HMF content of jam produced at atmospheric pressure was also found to be excessively high compared to the jam produced under vacuum. As it has been foreseen in the beginning of the study, vacuum cooking has been effective in reducing the HMF content of the strawberry jam due to the low temperature application. Sensorial quality of the vacuum-processed strawberry jam was superior in terms of color, appearance, consistency, taste and overall acceptance comparing to the atmosphere processed jams. This data could be utilized to contribute to the development of a household vacuum cooking equipment and the opportunity to produce with less harmful ingredients in home environment.

Key words:

Evaporation, HMF, Jam, Strawberry jam, Vacuum Cooking