The production of high-quality foods requires the precise control of factors influencing their quality. The aim of this doctoral thesis was to monitor the influence of sterilization heating and storage time and temperature on selected parameters of model food matrix using suitable physical, chemical and sensory methods. Sterilized processed cheese was chosen as the model matrix. Processed cheeses are milk protein concentrates, produced by melting of mixture of natural cheeses, emulsifying salts, water and other dairy and/or non dairy ingredients. Desirable transformation of this mixture to homogenous, smooth, shiny mass with desired textural, structural, rheologic and sensory properties is caused by using high temperature (about 80-100 °C) during melting. Sterilized processed cheese is subjected to additional sterilization heating (above 100 °C) after production, significantly elongating its durability. The processed cheeses (dry matter 40 % w/w, fat in dry matter 45 % w/w) were analyzed in this work, the part of them was sterilized (117 °C 20 min). Cheeses were stored at various temperatures (cold 6 ± 2 °C, laboratory 23 ± 2 °C and elevated 40 ± 2 °C), sterilized cheeses for 2 years, non sterilized for 1 year. During storage, the samples for physical (instrumental measuring of colour and texture), chemical (assessment of fatty acids and aroma compounds) and sensory (paired preference test, ranking test and evaluation using scale) analyses were taken at regular intervals. The influence of sterilization heating and for another the influence of storage conditions on mentioned parameters were investigated. Non sterilized processed cheese kept their very good quality during all the declared durability (4 months), however, then the significant worsening of most sensory properties was observed. In consequence of sterilization heating the changes of cheese colour and texture were observed, confirmed by both sensory and instrumental assessment. The impairment of taste and aroma was also found. These changes are obvious immediately after production and differences were observed during all the durability. In the case of sterilized processed cheese, the significant impairment of single sensory properties was determined, the highest in the case of texture, taste and aroma. The results of instrumental techniques confirm conclusions from sensory evaluation. The measurements of colour and texture vindicate the formation of darker colour (increasing total difference of colour delta E*) and higher hardness (increasing Fmax) of sterilized processed cheeses, continuing during storage. The worsening of taste and aroma is in accordance with lower content of aroma active compounds and selected fatty acids.
| Identifer | oai:union.ndltd.org:nusl.cz/oai:invenio.nusl.cz:233345 |
| Date | January 2012 |
| Creators | Loupancová, Blanka |
| Contributors | Vávrová, Milada, Kráčmar, Stanislav, Fišera, Miroslav |
| Publisher | Vysoké učení technické v Brně. Fakulta chemická |
| Source Sets | Czech ETDs |
| Language | Czech |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis |
| Rights | info:eu-repo/semantics/restrictedAccess |
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