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Polymorphism of a highly asymmetrical triacylglycerol in milk fat: 1-butyryl 2-stearoyl 3-palmitoyl-glycerol

DOI: 10.1021/acs.cgd.2c00713 DOI Help

Authors: Yoga Pratama (University of Leeds; Diponegoro University) , Sam Burholt (University of Leeds; Diamond-Leeds Small Angle X-ray Scattering Facility) , Daniel L. Baker (University of Leeds) , Amin Sadeghpour (University of Leeds) , Elena Simone (Politecnico di Torino) , Michael Rappolt (University of Leeds)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Crystal Growth & Design , VOL 43

State: Published (Approved)
Published: September 2022
Diamond Proposal Number(s): 29590

Abstract: Milk fat has more than 200 triacylglycerols (TAGs), which play a pivotal role in its crystallization behavior. Asymmetrical TAGs containing short butyryl chains contribute to a significant portion of milk fat TAGs. This work aims to elucidate the crystallization behavior of asymmetrical milk fat TAGs by employing the pure compound of 1-butyryl 2-stearoyl 3-palmitoyl-glycerol (BuSP). The structural evolution of BuSP after being cooled down to 20 °C from the melt is evaluated by small- and wide-angle X-ray scattering (SAXS and WAXS) and differential scanning calorimetry (DSC). The temporal structural observation shows that BuSP crystallizes into the α-form with short and long spacings of 4.10 and 56.9 Å, respectively, during the first hour of isothermal hold at 20 °C. The polymorphic transformation of the α to β′ phase occurred after 4 h of isothermal hold, and the β′- to α-form fraction ratio was about 70:30 at the end of the isothermal experiment (18 h). Pure β′-form X-ray patterns are obtained from the BuSP powder with short spacings of 4.33, 4.14, and 3.80 Å, while the long spacing of 51.2 Å depicts a three-chain-length lamellar structure with a tilt angle of 32°. Corresponding DSC measurements display that BuSP crystallizes from the melt at 29.1 °C, whereas the melting of α- and β′-forms was recorded at 30.3 and 47.8 °C, respectively. In the absence of the β-form, the β′-polymorph is the most stable observed form in BuSP. This work exemplarily explains the crystallization behavior of asymmetrical milk fat TAGs and thus provides new insights into their role in overall milk fat crystallization.

Journal Keywords: Beverages; Crystal structure; Dairy products; Thickness; X-ray scattering

Diamond Keywords: Dairy Products

Subject Areas: Food Science, Chemistry

Instruments: DL-SAXS-Offline SAXS and Sample Environment Development

Added On: 15/09/2022 09:44

Discipline Tags:

Chemistry Organic Chemistry Food Science

Technical Tags:

Scattering Small Angle X-ray Scattering (SAXS)