Abstract
In this study, linoleic acid (LA) was encapsulated in the presence or absence of quercetin into a dual polymer system of whey protein and kappa-carrageenan using power ultrasound. Atomic Force Microscopy (AFM) and FlowCam imaging technology were used for imaging and size determination of nano-and micro-capsules. Differential scanning calorimeter (DSC) was used to determine the glass transition temperature (Tg) of the freeze-dried nanocapsules. In order to examine the effect of water activity (aw) on the release profile of the encapsulated LA, the nanocapsules were equilibrated over saturated salt solution conditions corresponding to the range of aw between 0.333 and 0.769 in evacuated desiccators at room temperature. Gravimetric measurements of the steady state linoleic acid (LA) contents were conducted. The anti-oxidant activity of quercetin and the stability of encapsulated LA toward long term and thermally induced rancidity was investigated. The capsules were in the nanosize regime and 83% of the LA was effectively encapsulated. Furthermore, at aw of 0.764, the highest percentage of LA (74%) was released from the expelling nanocapsules. Quercetin was found to exhibit protective antioxidant effect against time-dependent oxidation and thermally induced rancidity of LA. Water activity values of 0.662 and 0.764 provided ideal humidity and pressure conditions for sustained release of nanoencapsulated LA at room temperature.
Highlights
Encapsulation is known as one of the “nature made” techniques for protecting biological structures [1]
Since the encapsulation was conducted at the same ultrasound frequency, it can be assumed that the capsules were first produced at a nanosize and possibly underwent aggregation or agglomeration during drying and storage resulting in an increased size. 3.2
These results indicate that nanoencapsulation provides a minimum protection against oxidative attacks, and quercetin is a potential antioxidant for linoleic acid, exhibiting antioxidant activity relatively closed to that of α-tocopherol
Summary
Encapsulation is known as one of the “nature made” techniques for protecting biological structures [1]. Encap- sulation is used in product formulation to entrap essential ingredients into a carrier, in order to impart protection against oxidation, isomerization, and degradation; and to extend the shelf life of materials over a period of time [1]. Encapsulation can be used for controlled/sustained delivery of functional substances when ingested in the body. This means, the unstable constituents should re- main intact for a certain period of time in the digestive system and released in the intestine over a range of physiological conditions [2]. Nanomaterials, objects having one dimension in the nanometer regime below 100 nm, [4] take advantage of their dramatically increased surface area to volume ratio. When brought into a bulk system, nanomaterials can strongly influence the mechanical and textural properties, such as stiffness and elasticity [5,6]
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