Effect of solubilised carbon dioxide at low partial pressure on crystallisation behaviour, microstructure and texture of anhydrous milk fat

Abstract

The crystallisation and melting behaviour, fat polymorphs, microstructure and texture of anhydrous milk fat (AMF) was investigated in the presence of dissolved CO (0-2000ppm) under two crystallising conditions (non-isothermal versus isothermal). CO was found to induce higher onset crystallisation temperature during cooling from 35 to 5°C at 0.5°Cmin. X-ray scattering analysis showed that, in the presence of dissolved CO this rapid crystallisation caused the formation of unstable, α polymorph fat crystals. For milk fat crystallised under isothermal condition at 25°C for 48h, dissolved CO improved solid fat content, slightly depressed melting temperature and exhibited a sharper melting peak. Microstructure of AMF visualised by Polarised light microscopy of crystallised AMF showed that increasing dissolved CO concentration was associated with smaller crystal size and greater crystal number. The bulk properties of the fat appeared to mirror the microstructural differences, in that the texture of CO-treated AMF was harder under isothermal condition but became softer than untreated AMF under cooling condition. The results of this study are of significance in understanding how CO treatment might be used to modulate the crystallisation behaviour of milkfat and thereby the structural development and physical functionality of fat-containing dairy products.

Butter and Dairy Fat Spreads

“…Influence of carbon dioxide (CO 2 ) on crystallization and bulk properties of milkfat has been studied recently (Truong, Palmer, Bansal, & Bhandari, 2017;Truong, Palmer, Bansal, Bhandari, & Hub, 2018). Mechanisms and kinetics of nucleation and crystal growth can be influenced by dissolved or suspended entities present in the fat.…”

“…Due to rapid crystallization, unstable species of α-form crystals were formed together with β′ and β polymorphs whereas non-treated AMF exhibited only β′ and β fat polymorphs. Increasing dissolved CO 2 concentration further to 2000 ppm was associated with relatively smaller sized crystals with two-to threefold increase in crystal numbers and solid fat content during isothermal crystallization at 28 °C for 20 min (Truong et al, 2017). Carbonation in cream and butter has also been investigated to study its effect on microbial stability, flavour and keeping quality (Hunziker, 1924;Prucha, Brannon, & Ruehe, 1925).…”

Effect of dissolved carbon dioxide on the sonocrystallisation and physical properties of anhydrous milk fat

“…Our previous research demonstrated the effect of dissolved CO 2 at low pressure on crystallisation, microstructural and textural properties of AMF (Truong et al, 2017a). This study has shown that, depending on crystallisation conditions, the effects of CO 2 mirror those M A N U S C R I P T…”

“…In a previous study, we demonstrated that infused carbon dioxide (CO 2 ) can also be used to modulate crystallisation behaviour, microstructure and texture of AMF (Truong, Palmer, Bansal, & Bhandari, 2017a) and that some of these effects are similar to those seen in sonocrystallisation. That is, dissolved CO 2 enhanced crystallinity, accelerated crystal nucleation and induced a larger number of smaller crystals than observed in untreated AMF.…”

“…Compared with untreated AMF, the texture of carbonated AMF was harder under isothermal crystallisation (25 °C) but softer when crystallised by rapid cooling from 35 to 5 °C. In this system, it was suggested that CO 2 molecules acted as impurities to enhance crystallisation, with CO 2 microbubbles also providing templates for heterogeneous crystal nucleation (Truong et al, 2017a).…”