7. Food applications of OBs
OBs as natural emulsions have shown prospects in the preparation of
liquid or semi-liquid food
products such as milk, yogurt, mayonnaise
and salad dressings (Nikiforidis et
al., 2012).
Consumer demand for cow’s milk alternatives has increased as a result of
lactose intolerance of some people and the demand for vegetarianism and
health (Aydar, Tutuncu & Ozcelik, 2020).
Plant-based
milk substitute (PBMS) is often
perceived as healthy possibly due to they contain dietary fiber,
vitamins, minerals, and antioxidants (Jeske, Zannini & Arendt, 2018).
Generally,
PBMS
is emulsified systems composed of
OBs,
solid particles and starch granules all dispersed in an aqueous phase
and the presence of water-soluble proteins on the surface of the OBs
(e.g. oleosins, caleosins, and steroleosins) improves the texture,
stability and nutrition of PBMS
(Huang, 2018; Zaaboul, Raza, Cao & Yuanfa, 2019). Ultrafiltration is
commonly used to produce an OBs-based emulsion with a lipid content
similar to cow milk and rich in polyunsaturated and monounsaturated
fatty acids to obtain PBMS and the PBMS can maintain its aroma
characteristics and bioactive constituents upon heating and exhibit
appreciable microbial, physical and oxidative storage stability (Naziri,
Koupantsis, Mantzouridou, Paraskevopoulou, Tsimidou & Kiosseoglou,
2017). Shakerardekani, Karim & Vaseli (2013) prepared pistachio milk by
using pistachio OB as a natural pre-emulsified emulsion and adding 5.0%
sugar, 0.02% vanilla and 0.0% salt.
Fat globules play an important role
in the production of yogurt. The acidification of milk induces the
formation of continuous gel networks of aggregated protein molecules
where fat globules are incorporated (Horne, 1999). The strength of the
gel depends on the size of the fat globules and the extent of their
surface interactions with the gel network (Kirimlidou et al., 2017). The
physical properties and microstructure of the gel are reflected in the
texture and sensory characteristics of yogurt (Öztürk, Aydın, Sözeri,
Demirci, Sert & Akın, 2018). Gallier et al. (2012) studied the
differences in chemical, physical and structural properties between the
almond OBs, and bovine
milk
fat globules. It was found that almond
OBs contained mostly long-chain
unsaturated fatty acids, phytosterols and nosphingomyelin. Bovine milk
fat globules were rich in saturated fatty acids and cholesterol, larger
in size, and richer in sphingomyelin and phosphatidylethanolamine. The
monolayer
membrane
around almond OBs and the trilayer membrane around bovine fat globules
might affect the stability of the lipid droplets in a food matrix and
the way the lipids were digested. Mantzouridou, Naziri, Kyriakidou,
Paraskevopoulou, Tsimidou & Kiosseoglou (2019) replaced the cow milk
fat globules in yogurt with maize germ OBs, which had a good
acidification kinetic pattern, forming a liquid structure acidic gel and
the quality and stability of yogurt improved compared with that prepared
with whole cow milk. Romero-Guzmán, Köllmann, Zhang, Boom & Nikiforidis
(2020) obtained a plant-based mayonnaise by controlling the conditions
of the aqueous extraction process of OBs and co-extracted proteins and
soluble fibers.
8. Conclusion
and future perspectives
At present, the basic structure of
OBs
has been determined. The unique
conformation of the OBs
membranes makes the OBs highly
stable. This special structure can be used as reference for the
development of synthetic oil droplets such as interface stabilizers for
Pickering emulsions. It is necessary to study the interaction and
structural dynamics between phospholipid and protein molecules, and
investigate the mechanical properties of the OBs membranes to provide
the OBs membranes with stability and stretchability. In order to promote
large-scale extraction of OBs, it is necessary to design a process with
low cost, easy to be sustained, high yield and complete structure of
OBs. There has been a tendency to
develop alternative extraction processes including enzyme assisted
extraction and supercritical fluid extraction. Complete OBs extraction
can be realized under the condition of ensuring that the OBs membrane is
not destroyed by screening specific enzyme and adjusting operating
parameters. At the same time, high pressure, ultrasonic, microwave,
steam flash and other auxiliary processing technology can be developed
to achieve efficient extraction. The application of OBs dispersion as a
naturally pre-emulsified oil-in-water emulsion is a research hotspot. It
can be considered as an alternative to animal fat in the development of
healthier meat products to reduce fat percentage and improve fatty acid
profile. However, its
potential
allergenic behavior and toxicity cannot be ignored if put into actual
production and in vitro and in vivo studies are needed to
take care of the associated side effects. It is also worth exploring the
important functions of individual
OBs components.