Tehnološki postopek izdelave ter kemijska, mikrobiološka in senzorična kakovost trniča

Kastelec, Lara (avtor), Čanžek Majhenič, Andreja (mentor)

Trnič je tradicionalen slovenski mlečni izdelek iz skupine sirov, ki so ga včasih izdelovali pastirji na Veliki planini, danes pa ga izdelujejo le še redki posamezniki. Za namen naše naloge smo obiskali gospo Kropivšek, ki nam je velikodušno pokazala tehnološki postopek izdelave trniča. Izdeluje se iz kislega in posnetega mleka, posebnost pri trniču pa je zadnja faza, ki je pri klasičnih siriščnih sirih faza zorenja, pri trniču pa je to bolj faza sušenja kot zorenja. Namen naloge je bil spoznati tradicionalen postopek izdelave, analizirati kemijsko sestavo ter senzorično opisati trnič. Tako smo v okviru kemijskih analiz določali vsebnost beljakovin, maščob, suhe snovi in soli v vzorcih različno dolgo sušenih trničev. Za pripravo prehranske tabele smo uporabili rezultate analiz konzumno zrelih vzorcev trničev, sušenih en mesec. Iz rezultatov analiz suhe snovi, določene z gravimetrično metodo ISO 5534, in maščob, določene z gravimetrično metodo ISO 1735, smo trniču lahko določili tip sira po vsebnosti vode oz. konsistenci in tip sira po vsebnosti maščobe. Izkazalo se je, da trnič spada med zelo trde sire za ribanje in tričetrtmastne sire. Z metodo za določanje vsebnosti dušika v vzorcu ISO 8968-3 pa smo določili 42 % beljakovin ter z metodo določanja vsebnosti kloridov ISO 2970 okoli 4 % soli. Sir smo ovrednotili tudi mikrobiološko, in sicer smo z metodo štetja na petrijevih ploščah ugotavljali kultivabilnost mlečnokislinskih bakterij po različnih časih sušenja. Ker je za vsa živila, tako tudi za mlečne izdelke oz. natančneje sire, zelo pomembna senzorična kakovost, smo na koncu trnič tudi senzorično opisali, in sicer po 20 točkovni lestvici. Ocenjevali smo zunanji izgled oziroma obliko, barvo, konsistenco testa, prerez, vonj in okus.

• Jezik: Slovenski jezik
• Ključne besede: mlečni izdelki, sir, tradicionalni slovenski sir, trnič, tehnološki postopki, kisanje mleka, sušenje, kemijska sestava, maščobe, beljakovine, sol, suha snov, mikrobiološke značilnosti, mlečnokislinske bakterije, senzorična kakovost
• Vrsta gradiva: Magistrsko delo/naloga
• Tipologija: 2.09 - Magistrsko delo
• Organizacija: BF - Biotehniška fakulteta
• Založnik: [L. Kastelec]
• Leto izida: 2020
• PID: 20.500.12556/RUL-124135
• UDK: 637.354:543.2/.9
• COBISS.SI-ID: 48502531
• Datum objave v RUL: 06.01.2021

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Technological procedure and chemical, microbiological, and sensorial quality of trnič

Izvleček

Trnič is a traditional Slovenian dairy product from the group of cheeses, which used to be made by herdsmen on Velika planina, but today it is only made by few individuals. For the purpose of our thesis, we visited Mrs. Kropivšek, who generously showed us the technological process of trnič making. Trnič is made from soured and skimmed milk, where its peculiarity is the last phase of manufacture, which is the ripening phase for traditional rennet-coagulated cheeses, while for trnič it is more like drying than ripening phase. Our goal was to learn about technological procedure of trnič production, to analyse chemical structure and to determine sensory characteristics. Thus, in the framework of chemical analyses, we determined protein, fat, dry matter and salt content in trnič samples, dried for various lenght of time. The preparation of the nutritional table based on the results of analyzes of consumable mature trnič samples and which is achieved at one month of trnič drying. From the results of analyzes of dry matter determined by ISO 5433, and fats determined by the gravimetric method ISO 1735, we were able to determine the cheese type according to the water content or texture and cheese type according to fat content. It turned out that trnič belongs to the type of very hard grated cheeses and ¾ fat cheeses. The ISO 8968-3 method was used to determine the nitrogen content in the sample which revealed the content of 42 % of proteins and the ISO 2970 method for determining the chloride content revealed the content of about 4 % of salt. The cheese was also evaluated microbiologically, using the count plate method on petri dishes to determine the cultivability of lactic acid bacteria after various length of drying. As for all foods, for dairy products or more precisely, cheeses as well, sensorial quality is of great importance, therefore samples of trnič were also sensory described, in accordance with a 20-point scale. We evaluated the exterior appearance or shape, color, texture, cross section, smell and taste.

• Ključne besede: dairy products, cheese, traditional Slovenian cheese, trnič, technological processes, acidification of milk, straining, drying, chemical composition, fats, proteins, salt, dry matter, microbiological properties, lactic acid bacteria, sensory quality