Uticaj odabranih faktora na tok kisele i sirišne koagulacije kozjeg mleka i kvalitet jogurta i sireva
Influence of selected factors on the acid and rennet coagulation of goat's milk and the quality of yoghurts and cheeses
Докторанд
Hovjecki, MarinaМентор
Miočinović, JelenaЧланови комисије
Puđa, PredragIličić, Mirela
Rac, Vladislav
Mirković, Milica M.
Метаподаци
Приказ свих података о дисертацијиСажетак
rasta. Njegov značaj sa socijalno-ekonomskog stanovišta posebno je veliki u pojedinim
regionima, gde se znatna količina proizvedenog mleka koristi za konzumiranje ili prerađuje u
veliki broj varijeteta sireva, koji često nose oznaku geografskog porekla, kao i jogurt.
Cilj ove disertacije je bio da se detaljnije prouči efekat niza odabranih faktora na
reološke parametre kisele i sirišne koagulacije kozjeg mleka, svojstva dobijenog gela kao i
kvalitet proizvedenih jogurta i sireva. Za istraživanje je korišćeno mleko dve rase koza, Sanske
i Alpske i obuhvaćena su sva tri laktaciona perioda (rani, srednji i kasni).
Iako je fizičko-hemijski sastav kozjeg mleka veoma sličan kravljem, razlike na nivou
strukture i svojstava pojedinih komponenata kozjeg mleka, pre svega proteina, predstavljaju
uzrok njegovih drugačijih tehnoloških svojstava i značajan su faktor koji utiče na inferiorniju
teksturu proizvedenog jogurta ili manji randman sira. Sa druge strane, pojedini procesni
parametri u proizvo...dnji mlečnih proizvoda, poput termičke obrade mleka ili dodavanja
kalcijum-hlorida, imaju dobro poznat efekat na kravlje mleko, ali njihov uticaj na kozje mleko
je često drugačiji, zbog čega se postavlja pitanje njihove adekvatne primene. Ovo polje
ispitivanja je još uvek otvoreno i potrebna su dodatna istraživanja u cilju optimizacije
tehnoloških postupaka proizvodnje kozjih mlečnih proizvoda.
Kako bi se istražio uticaj pojedinih faktora na svojstva kozjeg mleka tokom kisele i
sirišne koagulacije kao i mogućnosti unapređenja kvaliteta jogurta i sireva, u okviru ove
disertacije obavljen je niz ogleda.
U prvom delu disertacije ispitan je uticaj dodatka izolata proteina mleka na reološka
svojstva kisele koagulacije i kvalitet jogurta od kozjeg i kravljeg mleka, kako bi se utvrdile
mogućnosti primene ovog dodatka za poboljšanje teksture kozjeg jogurta u poređenju sa
jogurtom od kravljeg mleka.
U drugom delu je istražen uticaj enzima transglutaminaze i dva termička tretmana
mleka na tok kisele koagulacije kozjeg mleka i teksturu jogurta tokom perioda skladištenja.
Efekti ovog enzima, termičkih tretmana i acidifikacije pod dejstvom starter kulture na proteine
mleka i jogurta određeni su elektroforetski. Takođe, ispitan je i uticaj ovog enzima na
preživljavanje starter kulture tokom skladištenja i obavljena je senzorna ocena ovih proizvoda.
Efekti tri termička tretmana (72 °C/30 s, 85 °C/5 min i 95 °C/5 min) istraženi su u
narednom delu ogleda u pogledu reoloških svojstava kiselog gela i teksture jogurta čvrstog tipa
(eng. set style). Ovom prilikom je ispitan i uticaj koji ovi tretmani imaju na prosečnu veličinu
kazeinskih micela metodom dinamičkog rasejanja svetlosti i proteinski profil tretiranih mleka.
Sledeći segment disertacije obuhvatio je reološka ispitivanja uticaja niza faktora na tok
sirišne koagulacije mleka i svojstva sirišnog gela. U okviru ovih ogleda ispitani su navedeni
faktori: 1) koncentracija sirila (0,054 g/l, 0,020 g/l, 0,015 g/l i 0,010 g/l); 2) pH mleka (6,5, 6,3
i 6,1); 3) temperatura koagulacije (27, 31 i 35 °C); 4) period laktacije (rani, srednji i kasni) i 5)
termički tretmani mleka i dodatak kalcijum-hlorida (65 °C/30 min, 80 °C/5 min i 90 °C/5 min,
bez ili sa dodatkom 200 mg/l CaCl2)...
Goat's milk is a nutritionally high-value food whose production in the world has a
growing trend. Its importance from the socio-economic point of view is especially great in some
regions, where a significant amount of this milk is used for consumption or processed into a
large number of varieties of cheeses, which often posess a geographical indication, and yogurt.
The aim of this dissertation was to study in more detail the effect of a number of selected
factors on the rheological properties of acid and rennet coagulation of goat's milk, the
characteristics of the obtained gel as well as the quality of produced yoghurts and cheeses. Milk
from two breeds of goats, Saanen and Alpine, was used for the research and all three lactation
periods (early, middle and late) were included.
Although the physicochemical composition of goat's milk is very similar to cow's milk,
differences in the structure and properties of individual components of goat's milk, primarily
proteins, are the cause of i...ts different technological properties and are a significant factor
affecting the inferior texture of yoghurt or lower yield of final cheese. On the other hand, certain
process parameters in the production of dairy products, such as heat treatment of milk or
addition of calcium chloride, have a well-known effect on cow's milk, but their impact on goat's
milk is often different, which raises the question of their adequate application. This field of
research is still open and further research is needed in order to optimize the technological
procedures of goat dairy production.
In order to investigate the influence of certain factors on the properties of goat's milk
during acid and rennet coagulation, as well as the possibility of improving the quality of yogurt
and cheese, a series of experiments was performed within this dissertation.
In the first part of the dissertation, the influence of milk protein isolate on the rheological
properties of acid coagulation and the quality of goat's and cow's milk yogurt was examined, in
order to determine the possibilities of using this supplement to improve the texture of goat's
yogurt compared to cow's milk yogurt.
In the second part, the influence of the enzyme transglutaminase and two heat
treatments of milk on the course of acid coagulation of goat milk and the texture of yogurt
during the storage period was investigated. The effects of this enzyme, heat treatments and
acidification under the action of starter culture on milk and yoghurt proteins were determined
electrophoretically. Also, the influence of this enzyme on the survival of starter culture during
storage was examined and a sensory evaluation of these products was conducted.
The effects of three goat milk heat treatments (72 °C/30 s, 85 °C/5 min and 95 °C/5 min)
were investigated in the next part of the experiment in terms of rheological properties of acid
gel and texture of set type yogurt. On this occasion, the influence that these treatments have on
the average size of casein micelles by the method of dynamic light scattering and the protein
profile of treated milk was also examined.
The next segment of the dissertation included rheological investigations of the influence
of a number of factors on the course of rennet coagulation of milk and the properties of rennet
gel. Within these experiments, the following factors were examined: 1) rennet concentration
(0.054 g/l, 0.020 g/l, 0.015 g/l and 0.010 g/l); 2) milk pH (6.5, 6.3 and 6.1); 3) coagulation
temperature (27, 31 and 35 °C); 4)lactation period (early, middle and late) and 5) heat
treatments of milk and addition of calcium chloride (65 °C/30 min, 80 °C/5 min and 90 °C/5
min, without or with the addition of 200 mg/l CaCl2)...
Факултет:
Универзитет у Београду, Пољопривредни факултетДатум одбране:
01-06-2021Пројекти:
- Унапређење и развој хигијенских и технолошких поступака у производњи намирница животињског порекла у циљу добијања квалитетних и безбедних производа конкурентних на светском тржишту (RS-MESTD-Integrated and Interdisciplinary Research (IIR or III)-46009)