Abstract

Chocolate is a complex rheological system in which non-fat cocoa particles and sugar particles are enveloped by crystal matrix of cocoa butter. Physical properties of chocolate depend on ingredient composition, method of production and properly performed pre-crystallization phase. In this work, chocolate was produced in an unconventional way, i.e. in a ball mill applying variable refining time (30, 60 and 90 min) and pre-crystallization temperature in chocolate masses (26, 28 and 30?C). Two types of chocolate were produced: chocolate with 20% of powdered cow?s milk (R1) and chocolate with 20% of soya milk powder (R2). The quality of chocolate was followed by comparing nutritive composition, 23 polyphenol content, hardness of chocolate, solid triglyceride content (SFC) and rheological parameters (Casson yield flow (Pa), Casson viscosity (Pas), the area of the thixotropic loop, elastic modulus and creep curves). The aim of this paper is determining changes caused by replacing cow?s milk with soya milk powder in respect of nutritive, rheological and sensory properties, as well as defining optimal parameters: precrystallization temperature and refining time of soya milk chocolate in order to obtain suitable sensory and physical properties identical to those of milk chocolate mass. The results show that replacing powdered cow?s milk with soya milk powder affects the increase in nutritive value of soya milk chocolate. R2 chocolate mass showed the increase in essential amino acids and fatty acids. This chocolate mass also showed the increase in total polyphenols by 28.1% comparing to R1 chocolate mass. By comparing viscosity, yield stress, shear stress and the area of the thixotropic loop, it can be observed that R1 chocolate mass represents a more organized and simpler system than the mass with soya milk (R2), as it shows lower values for all the above mentioned parameters, regardless of the refining time and pre-crystallization temperature. Viscoelastic behavior of R2 is also evident, as a consequence of soya protein presence. In order to maintain optimal hardness as well as melting resistance of chocolate, in case of R2 chocolate mass it is necessary to apply pre-crystallization temperature of 26?C, while for the chocolate mass R1 it is 30?C.

Highlights

  • Lipidi su uklonjeni iz uzoraka čokolade, tako što se 2 g uzorka ekstrahovano tri puta sa 10 ml heksana

  • Nakon 2 h merena je apsorbancija na 750 nm (Ultraspec 3300 pro, Amersham Bioscience, Sweden)

  • Comparative analysis of SFC in R1 and R2 chocolate masses depending on pre-crystallization temperature and refining time: a) 30 b) 60 and c) 90 min

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Summary

NAUČNI RAD

Proces proizvodnje čokolade je detaljno proučen i sa malim odstupanjima u konstrukciji uređaja, poznat već oko 150 godina. Kompanija Mazzeti je konstruisala kuglični mlin sa rezervoarom za skladištenje čokoladne mase, koji je snabdeven tankoslojnim isparivačem čime se čokoladnoj masi koriguje viskozitet i ukus [5]. Kuglični mlin zamenjuje dve faze u standardnom procesu proizvodnje čokoladne mase: usitnjavanje i končiranje koje se dešavaju istovremeno. Mehaničkim putem, odnosno dugotrajnim mešanjem, mlevenjem i stalnom recirkulacijom čokoladne mase pri određenoj temperaturi, dobija se stabilna suspenzija čvrstih čestica u kakao maslacu [8]. Na reologiju čokolade najveći uticaj ima sirovinski sastav, sadržaj masti, izbor emulgatora, raspodela veličine čvrstih čestica i način pakovanja čestica. Sadržaj čvrstih triglicerida (SČT) u očvrsloj čokoladi zavisi od sastava masne faze, kao i od pravilnog vođenja postupka kristalizacije kakao maslaca i definiše se kao odnos tečne i čvrste faze na datoj temperaturi. Novija istraživanja ukazuju da proteini mleka smanjuju antioksidativnu aktivnost mlečne čokolade, u poređenju sa crnom čokoladom [31]

EKSPERIMENTALNI DEO
Hemijska analiza čokoladne mase
Sadržaj ukupnih polifenola i antioksidativna aktivnost
Reološke osobine čokoladne mase
Određivanje čvrstoće čokolade
REZULTATI I DISKUSIJA
Histidin Fenilalanin Glutamat Aspartat
Određivanje sadržaja čvrstih triglicerida
Reološke karakteristike čokoladnih masa
Faza Creep
Dinamička oscilatorna merenja
Findings
SUMMARY

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