Browsing by Subject "ICP-OES"

The literature review of this master’s thesis dealt with major and minor mineral composition of strawberries and the factors affecting it. In addition, the effect of jam production on mineral profile and jam adulteration as a phenomenon were discussed as well as using the mineral profile to detect food adulteration using statistical multivariate methods. The aim of the experimental part of this thesis was to study if the mineral profile in combination with statistical multivariate methods could be used to point out the authenticity of strawberry jam. Alterations in the strawberry mineral profile were studied by determining the mineral profile of several different strawberry samples (n = 51). In addition, the strawberry data was used to create models for classification of other samples. The operability of the method was tested using “forged” model jams created by mixing strawberry jam with apple, pear or pumpkin jam (5 %, 10 %, 20 % and 50 %). The differentiation of mineral profiles of other plant species (n = 10) from strawberry mineral composition was tested with small-scale data. Additionally commercial strawberry jams (n = 33) were tried to classify by their mineral profile to be authentic or adulterated. Mineral profiles (Al, B, Ca, Cd, Cu, Fe, K, Mg, Mn, Mo, P, Pb, S, Si and Zn) were quantified with inductively coupled plasma – optical emission spectrometry (ICP–OES). Sample pretreatment included freeze drying, grinding, wet digestion using nitric acid and hydrogen peroxide and dilution with water. Quantification was based on external standard method. Results were processed by principal component analysis (PCA) and soft independent modelling of class analogies (SIMCA). Fabricated model jams and pure apple, pear and pumpkin jams could be separated from strawberry jam both with principal component analysis and with using SIMCA method to classify them to be something else than strawberry jam with 95 percent probability. Most accurate classification was obtained with mineral profiles combining Mg, P, S, Ca and K or Mg, P, S, Mn, Ca and K. Other plant species studied had different mineral profiles compared to strawberries with exception of raspberry. No clear groups were formed on principal component analysis of the strawberry data in respect to cultivar, growth place or time. The method was not yet applicable for the use of classifying commercial strawberry jam samples reliably. There is a need for additional studies about the effect of ingredients used for jam production on the classification. Also the separation between mineral profiles of species related to strawberries should be studied further. In addition mineral profile library of strawberries for industrial processing should be created in order to classify commercial strawberry jam samples. Based on the separation results of fabricated model jams and authentic strawberry jam the method seems to be suitable for further development at least for detecting strawberry jam adulteration by extending with apple, pear or pumpkin.