Application of Spectroscopic in the Study of Milk Fat in Dairy Cream
WANG Yun-na1, LI Yan2, LI Yang1, YIN Wei-hua1, ZHANG Lie-bing1*
1. College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China
2. School of Food and Chemical Engineering, Beijing Technology and Business University, Beijing 100048, China
Abstract：Milk fat is the main raw constituent of dairy cream. The source of the milk has a significant influence on its physicochemical properties and the presence of the dispersed phase in the emulsion, which, in turn, influences the quality of cream products. In this paper, Raman spectroscopy combined with dynamic light scattering, near infrared spectrum-stability analysis, and other spectroscopy techniques were used to study the physiochemical characteristics of milk fat from three different sources, namely MF-A, MF-B and MF-C, and to compare the corresponding stability of dairy cream. The Raman spectra results indicatedthat 1 303 and 1 446 cm-1 were —CH2 vibrations, 2 800～3 000 cm-1was a C—H vibration, and 1 131 cm-1 was a C—C vibration, ith a peak intensity of MF-A>MF-B>MF-C (p<0.05). These results established that MF-A had the highest degree of saturation. 1 657 cm-1 was a C=C cis-stretching vibration, thus indicating that all samples contained cis-unsaturated fatty acids and had no trans-fatty acids. The peak intensity was MF-C>MF-B>MF-A (p<0.05), indicating that MF-C had the highest cis-unsaturated fatty acid content. Iodine analysis further showed that MF-A had the highest degree of saturation. Solid fat content (SFC) at different temperatures showed MF-A>MF-B>MF-C (p<0.05) in the heat range of 0～40 ℃. Therefore, dairy cream should be stored at around 4 ℃ and whipped cream at between 10 and 15 ℃. After isothermal crystallization at 25 ℃ for 1 h, the three samples were observed under a polarized light microscope: MF-A, which had a low iodine value and a high melting point, formed the nucleus quickly and induced the surrounding fat to crystallize continuously until aggregated to form a dense crystalline network; MF-B exhibited a combination of spherulites and needle-like crystals, and the crystal network was incomplete; MF-C crystals were sparsely distributed with the diameter of each crystal less than 20 μm. Subsequently, dairy creams XMF-A, XMF-B and XMF-C were prepared using MF-A, MF-B and MF-C, respectively. As can be seen in the particle size distribution chart, XMF-A is basically unimodal, suggesting that the cream emulsion was relatively stable and the fat globules were not coalesced. Both XMF-B and XMF-C are bimodal, suggesting partial coalescence of the fat globules, with XMF-C’s degree of coalescence greater than that of XMF-B, providing XMF-C with the largest average particle size. The dynamic light scattering results recorded the average particle size of milk fat globules as follows: XMF-Ap<0.05). The near infrared transmission map showed that the transmission of XMF-A and its variable range were relatively small, signifying that there was no obvious serum loss or flocculation in the cream system. Both XMF-B and XMF-C had a relatively high transmission, especially XMF-C which had a narrow and sharp transmission area, indicating instability during the centrifugation process, in which severe lactation, fat floating and opacity were apparent. The space stability of the system was recorded as XMF-A>XMF-B>XMF-C (p<0.05). The results of this research, which examines the physicochemical properties of milk fats in their continuous/dispersive phase and the mechanism of milk fat composition and crystallization behavior on dairy cream quality, thus provide a theoretical basis for the selection of raw materials in the preparation of a variety of dairy products.
王筠钠，李 妍，李 扬，尹未华，张列兵. 光谱学技术在稀奶油乳脂肪研究中的应用[J]. 光谱学与光谱分析, 2019, 39(06): 1773-1778.
WANG Yun-na, LI Yan, LI Yang, YIN Wei-hua, ZHANG Lie-bing. Application of Spectroscopic in the Study of Milk Fat in Dairy Cream. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(06): 1773-1778.
[1] WANG Xiang, DAI Chang-jian(王 翔, 戴长建). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2015, 35(4): 929.
[2] Ullah R, Khan S, Khan A, et al. J. Raman Spectrosc., 2017, 48(3): 363.
[3] Zhou X, Chen L, Han J, et al. Int. J. Food Pro., 2016, 20(10): 2223.
[4] Tzompa-Sosa D A, Ramel P R, Van Valenberg H J, et al. J. Agr. Food Chem., 2016, 64(20): 4152.
[5] Queirós M S, Grimaldi R, Gigante M L. Food Res. Int., 2016, 84: 69.
[6] ZHAO Fang, PENG Yan-kun(赵 芳, 彭彦昆). Chinese Journal of Lasers(中国激光), 2017, 44(11): 1111001.
[7] Buyukbese D, Rousseau D, Kaya A. Int. J. Food Pro., 2018, 20(3): 3015.
[8] Bayard M, Leal-Calderon F, Cansell M. Food Chem., 2017, 218: 22.
[9] Thiel A E, Hartel R W, Spicer P T. Journal of the American Oil Chemists’ Society, 2017, 94(2): 325.
[10] Edén J, Dejmek P, Löfgren R, et al. Int Dairy J, 2016, 61: 176.
