doctoral thesis
Influence of ingredients on rheological properties of chocolate masses and stability of chocolates

Svjetlana Škrabal (2009)
Josip Juraj Strossmayer University of Osijek
FACULTY OF FOOD TECHNOLOGY
Department of Food Technologies
Sub-department of Carbohydrates Technology
Metadata
TitleUtjecaj sastojaka na reološko ponašanje čokoladnih masa i stabilnost čokolada
AuthorSvjetlana Škrabal
Mentor(s)Drago Šubarić
Abstract
U ovome radu je ispitivan utjecaj sastojaka (mlijeka u prahu, zamjenske masti, paste od lješnjaka, emulgatora: lecitina, poliglicerol poliricinoleata i estera limunske kiseline i mono i diglicerida masnih kiselina, pojedinačno i u smjesama) i vremena končiranja na reološka svojstva čokoladnih masa te utjecaj mlijeka u prahu, zamjenske masti i paste od lješnjaka te uvjeta čuvanja (temperature i vlažnosti zraka) na pojavu sivljenja površine čokolade. Reološka svojstva mjerena su Brookfield-ovim rotacijskim viskozimetrom. Za praćenje sivljenja površine uzoraka korišten je tristimulusni kromametar, a pomoću diferencijalne motridbene kalorimetrije (DMK) praćena je promjena sastava površinskog sloja čokolade u cilju utvrđivanja mehanizma migracije masti na površinu. Rezultati istraživanja pokazali su da vrste i svojstva sirovina imaju značajan utjecaj kako na reološka svojstva čokoladnih masa tako i na stabilnost čokolada prema sivljenju. Tip mlijeka u prahu je značajno utjecao na reološka svojstva čokoladnih masa, pri čemu su mase s mlijekom sušenim na valjcima imale niže vrijednosti reoloških parametara. Utjecaj emulgatora na reološka svojstva čokoladnih masa u značajnoj mjeri je ovisio o svojstvima ostalih sirovina, prije svega mlijeka u prahu. Ester limunske kiseline i mono i diglicerida masnih kiselina pokazao se kao učinkovito sredstvo za podešavanje granice tečenja i plastične viskoznosti čokoladnih masa, kako pojedinačno tako i u kombinaciji s ostalim emulgatorima, prije svega s poliglicerol poliricinoleatom. Utvrđeno je da se u slučaju priprave čokoladnih masa s mlijekom u prahu dobivenim na valjcima i uz lecitin kao emulgator vrijeme priprave mase može skratiti, a da se dobiju proizvodi željenih reoloških svojstva. Kombiniranjem emulgatora, ovisno o sastavu čokoladnih masa, postignuti su pozitivni učinci na reološka svojstva čokoladnih masa koji se ne mogu postići primjenom pojedinačnih emulgatora. Udio i vrsta pojedinih sastojaka, kao i vlažnost zraka tijekom skladištenja, imali su značajan utjecaj na pojavu sivljenja površine čokolada. Čokolade koje su sadržavale mlijeko u prahu sušeno na valjcima bile su otpornije na sivljenje zbog činjenice da mlijeko sušeno na valjcima sadrži veći udio slobodne mliječne masti koja je inhibitor sivljenja. Čokolade koje su sadržavale masti s nižim talištem (pasta od lješnjaka) bile su sklonije sivljenju, već pri nižoj vlažnosti zraka. Uzorci koji su sadržavali kakao maslac ekvivalent (zamjenska mast) više su posivjeli u odnosu na one s istim udjelom ukupne masti koja je iz kakaovog maslaca i mliječnih komponenti. DMK mjerenjima posivljenog površinskog sloja čokolade dobile su se krivulje koje su poslužile za izračunavanje entalpije taljenja (ΔH). Tijekom skladištenja čokolade, posebno pri povišenoj relativnoj vlažnosti (75 %), došlo je do sniženja entalpije taljenja saharoze, a povećanja entalpije taljenja kakaovog maslaca, te se može zaključiti da je povećana vlažnost zraka utjecala na otapanje šećera u površinskim slojevima čokolade što je omogućilo izlazak masti na površinu.
Keywordschocolate rheological properties emulsifiers
Parallel title (English)Influence of ingredients on rheological properties of chocolate masses and stability of chocolates
Committee MembersVlasta Piližota (committee chairperson)
Drago Šubarić (committee member)
Zoran Herceg (committee member)
Tihomir Moslavac (committee member)
GranterJosip Juraj Strossmayer University of Osijek
FACULTY OF FOOD TECHNOLOGY
Lower level organizational unitsDepartment of Food Technologies
Sub-department of Carbohydrates Technology
PlaceOsijek
StateCroatia
Scientific field, discipline, subdisciplineBIOTECHNICAL SCIENCES
Food Technology
Engineering
UDK663
APPLIED SCIENCES. MEDICINE. TECHNOLOGY
Industrial microbiology. Industrial mycology. Zymurgy, fermentation industry. Beverage industry. Stimulant industry
Study programme typeuniversity
Study levelpostgraduate
Study programmeFood Engineering
Academic title abbreviationdr. sc.
Genredoctoral thesis
Language Croatian
Defense date2009-04-14
Parallel abstract (English)
Influence of ingredients (milk powder, vegetable fat, hazelnut paste, emulsifiers: lecithin, polyglycerol polyricinoleate, mono-diglyceride ester of citric acid, individually and in combinations) and conching time on rheological properties of chocolate masses, as well as influence of milk powder, vegetable fat and hazelnut paste on fat bloom of chocolate were investigated in this research. Rheological properties were investigated using Brookfield rotational viscometer. Fat bloom of chocolates was monitored using tristimulus chromameter and, in order to reveal mechanism of fat migration, change in composition of chocolate surface was determined by differential scanning calorimeter. Results showed that types and properties of ingredients significantly influenced both rheological properties and stability of chocolates towards fat bloom. Milk powder type had significant influence on rheological properties of chocolate masses, whereat masses with roller dried milk powder had lower values of rheological parameters. Influence of emulsifiers on rheological properties highly depended on properties of other ingredients, mainly milk powder. Mono-diglyceride ester of citric acid proved to be efficient regulator of rheological properties of chocolate masses, individually and in combinations, primarily with polyglycerolpolyricinoleat. When chocolate masses where produced with roller dried milk powder and emulsifier lecithin, time of chocolate mass preparation could be reduced without unwanted rheological effects. Combinations of emulsifiers positively influenced rheological properties of chocolate masses, in the way which couldn’t be achieved with individual emulsifiers. Content and type of ingredients, as well as relative humidity during storage significantly influenced fat bloom of chocolate. Chocolates containing roller dried milk powder were more resistant to fat bloom due to higher content of free milk fat, which is fat bloom inhibitor. Chocolates containing low melting fats (hazelnut paste) were more prone to fat bloom, even at lower humidity. Samples containing cocoa butter equivalents (vegetable fat) were more bloomed than samples containing same amount of fats from cocoa butter and milk powder. DSC curves, which were used for melting enthalpy (ΔH) calculations, were obtained from DSC analyses of grey layers from chocolate surfaces. During chocolate storage, especially at higher relative humidity (75 %) sucrose melting enthalpy declined, while cocoa butter enthalpy increased. This indicates that increased relative humidity caused sugar melting in surface layers of chocolate, which enabled migration of fat to the surface.
Parallel keywords (Croatian)čokolada reologija emulgatori
Extent143 str.; ilustr., graf. prikazi; 30 cm
Versionaccepted version
Resource typetext
Access conditionAccess restricted to students and staff of home institution
Terms of usehttp://rightsstatements.org/vocab/InC/1.0/
Noteaccepted version
URN:NBNhttps://urn.nsk.hr/urn:nbn:hr:109:615608
CommitterSanda Hasenay