3.5 Microstructure analysis
In conclusion, among FLWB, CLA-WB were closer to the quality of
commercial walnut butter. Therefore, the walnut butter with CLA addition
was selected for further microstructural analysis. Image analysis
provided information on the pixel organization of the different regions
of the samples (Backes and Bruno, 2013). The walnut butter samples
prepared with CLA were further analyzed using optical microscopy Fig. 7
showed the optical microstructure of walnut butter prepared by CLA and
commercially available walnut butter. The results indicated that all
walnut butter showed a porous matrix structure encasing the oil
droplets. Proteins were adsorbed on the surface of the oil droplets
while some of them formed aggregates between the oil droplets and the
proteins. The aggregation of SS1 and SS2 was higher while the oil
droplet size of SS1 was more homogeneous. Emulsion droplets with smaller
average particle size may result in a larger total interfacial area of
emulsion droplets and more adsorbed proteins (Farshchi et al., 2013),
thus preventing aggregation between oil droplets. The formation of high
oil content and low interfacial adsorbed proteins may result in unstable
oil droplets that tended to form aggregated large oil droplets (Fig.
7F). Due to protein and oil droplet interactions, FLWB had a particle
size and emulsion structure, which was similar to that of commercial
products (Xu et al., 2020). The results showed that the quality of
CLA-WB was closer to that of commercial walnut butter. Further
microscopic results showed that the particle size, distribution and
aggregation of CLA-6.5 were closer to the microstructure of commercial
walnut butter.
Conclusion
In this study, different types and additions of FL (MCT, DG, CLA) were
selected to prepare walnut butter. By measuring the physicochemical
properties of the three groups of samples, it was obtained that when the
addition ratio of CLA and defatted walnut meal was 6.5:3.5, the prepared
walnut butter had the similar properties to commercial walnut butter.
FLWB with similar processing physical properties and microscopic
morphology as commercial walnut butter could be obtained after vibratory
ball mill grinding. In addition, FLWB contained 65% CLA had higher
bioactive functions. This study provided a new way for the comprehensive
development and utilization of defatted walnut meal, which could help
the development of functional lipids walnut butter. Vibratory ball
milling technology was used to grind walnut butter in a single process
to streamline the milling process. which provided a new method for the
preparation of functional lipids walnut butter.