Vpliv vrste medu na tokovno vedenje

diplomsko delo

Sara Rovan (Author), Lidija Slemenik Perše (Mentor)

Abstract

Raziskave o reološkem vedenju medu so pomembne, saj je reološko vedenje povezano s senzoričnimi lastnostmi in je bistvenega pomena za nadzorovanje kakovosti produkta. Te raziskave nam dajejo pomembne informacije, kako med pravilno pridelamo, pakiramo, skladiščimo in ravnamo z njim. Na reološke lastnosti medu vplivajo številni dejavniki, kot je sestava in temperatura. Sestava in lastnosti medu so odvisne od vrste rastlin, iz katerih čebele nabirajo nektar oziroma mano, od geografskega izvora medu in podnebnih razmer, v katerih med dozori. Viskoznost je ena izmed najpomembnejših reoloških lastnosti medu, saj vpliva na njegovo kakovost. Tokovno vedenje medu največkrat merimo z rotacijskimi reometri z nastavljivo strižno napetostjo. Večina vrst medu izkazuje newtonsko vedenje, nekatere vrste pa se vedejo nenewtonsko s strižno odvisnim upadanjem viskoznosti. Viskoznost pri teh vrstah je časovno odvisna, govorimo o tiksotropiji. Razlog za takšno tokovno vedenje pripišemo koloidnim snovem v medu, ki imajo visoko molekulsko maso, kot so dekstrani in proteini. Nenewtonsko vedenje lahko opišemo z Herschel-Bulkley-jevim modelom, tiksotropijo pa z Weltmann-ovim. Poleg koloidnih snovi, kristalov in vsebnosti vode v medu vpliva na viskoznost tudi temperatura. Z Arrhenius-ovim modelom lahko natančno in najenostavnejše opišemo vpliv temperature na viskoznost medu ter določimo aktivacijsko energijo, ki nam poda informacijo, kako je viskoznost določene vrste medu občutljiva na spremembo temperature. V svojem diplomskem delu sem s pomočjo ustrezne literature proučevala proizvodnjo in sestavo medu, modele, s katerimi opišemo newtonsko in nenewtonsko vedenje ter modele za opis vpliva temperature na viskoznost medu. S pomočjo meritev iz objavljenih raziskav, sem proučila, kaj vpliva na tokovno vedenje in kako je viskoznost različnih vrst medu glede na različni geografski izvor odvisna od temperature.

Keywords

proizvodnja medu;sestava medu;tokovno vedenje;viskoznost;tiksotropija;diplomska dela;

Data

Language:	Slovenian
Year of publishing:	2022
Typology:	2.11 - Undergraduate Thesis
Organization:	UL FKKT - Faculty of Chemistry and Chemical Technology
Publisher:	[S. Rovan]
UDC:	532.135:638.16(043.2)
COBISS:	122500355
Views:	23
Downloads:	11
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	The influence of honey type on flow behaviour
Secondary abstract:	Research on the rheological behavior of honey is important, as rheological behavior is related to sensorial properties and is essential for product quality control. This research provides important information on how honey is properly produced, packaged, stored, and handled. The rheological properties of honey are influenced by many factors, such as composition and temperature. The composition and properties of honey depend on the type of plants from which bees collect nectar or honeydew, from the geographical origin of the honey and the climatic conditions in which it matures. Viscosity is one of the most important rheological properties of honey, as it affects its quality. The flow behaviour of honey is most often measured by controlled stress rheometers. Most types of honey exhibit Newtonian behaviour, while some of them are non-Newtonian with shear thinning flow behaviour. The viscosity of these types is usually also time-dependent, i.e.; thixotropic. The reason for such flow behavior is attributed to high molecular weight colloidal substances such as dextran and proteins. Non-Newtonian behaviour can be described by the Herschel-Bulkley model, and thixotropy by the Weltmann model. In addition to colloidal substances, crystals and water content in honey, the viscosity is also affected by temperature. With the Arrhenius model, we can accurately and simply describe the effect of temperature on the viscosity of honey and determine the activation energy, which gives us the information on how sensitive the viscosity of a particular type of honey is to changes in temperature. With the help of reported studies in the literature, I studied the production and composition of honey, models to describe Newtonian and non-Newtonian behaviour, and models to describe the effect of temperature on the viscosity of honey. Using measurements from published research, I studied what influences flow behaviour and how the viscosity of different types of honey of different geographical origins depends on temperature.
Secondary keywords:	honey production;composition of honey;flow behaviour;viscosity;thixotropy;Med;Reologija;Univerzitetna in visokošolska dela;
Type (COBISS):	Bachelor thesis/paper
Study programme:	1000372
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Fak. za kemijo in kemijsko tehnologijo, UNI Kemijsko inženirstvo
Pages:	42 str.
ID:	16327070