MICRO ENCAPSULATION USING HIGH-VOLTAGE, LOW-CURRENT, HIGH FREQUENCY ALTERNATING-CURRENT SPRAY ATOMIZATION
Disclosed is a spray drying system and process for encapsulating a core material, such as a volatile flavor oil, within a carrier or wall material. The process is achieved by atomizing a liquid emulsion comprising the core material, the wall material, and a liquid solvent, applying a high-voltage, low-current, high frequency alternating-current charge or a high-voltage, low-current, low frequency alternating-current charge at the site of atomization, and drying the atomized emulsion into an encapsulated, free-flowing powder. Applying a high-voltage, low current alternating-current at the site of atomization allows the spray drying to be accomplished at significantly reduced temperatures, in particular, at inlet temperatures in the range of 25° C. to 150° C., and outlet temperatures in the range of 25° C. to 110° C. The low drying temperatures impart improvements in the resulting encapsulated powdered product, including better retention of volatile flavor components, a flavor profile comparable to that of the starting liquid formulation, and better hydration and dissolution in water-based applications.
1 . A method for preparing an encapsulated product having a core component encapsulated within a wall material comprising the steps of:
forming an emulsion by emulsifying at least one core material with at least one liquid solvent and at least one wall material;
atomizing the emulsion into droplets using an atomizing gas and an atomizer connected to a high-voltage low-current alternating-current source that supplies a voltage charge to the droplets in the range of about 2 kV to about 200 kV;
spraying the charged droplets into a drying chamber;
drying the droplets in the drying chamber by contacting the droplets with a drying gas introduced into an inlet of the drying chamber, wherein the drying chamber has an inlet temperature set at about 25° C. to about 110° C.; and
collecting the dried droplets as the encapsulated product.
2 . The method of claim 1 , wherein the core material comprised 5% to 50% by weight, and the wall material comprises 50% to 98% by weight, based on the total dry weight of the core material and the wall material combined.
3 . The method of claim 1 , wherein the emulsion is introduced into the atomizer at a feed rate of about 20 ml/min to about 400 ml/min.
4 . The method of claim 1 , wherein the atomizing gas is an inert gas.
5 . The method of claim 4 , wherein the atomizing gas is pressurized at a pressure of 5 psi to 120 psi.
6 . The method of claim 1 , wherein the drying gas has an oxygen content of less than 5%.
7 . The method of claim 6 , wherein the drying gas has a flow rate of about 150 standard cubic feet per minute (scfm) to about 18,000 scfm.
8 . The method of claim 1 , wherein the method further comprises the steps of separating the drying gas from the dried droplets and recirculating the drying gas to the inlet of the drying chamber.
9 . The method of claim 8 , wherein the drying gas is processed to remove moisture before introducing the recirculated drying gas to the inlet of the drying chamber.
10 . The method of claim 8 , wherein the recirculated drying gas is mixed with nitrogen gas so that the drying gas has an oxygen content of less than 5% by volume.
11 . The method of claim 1 , wherein the wall material comprises at least one material selected from carbohydrates, proteins, gums, lipids, waxes, food grade polymers, celluloses, phospholipids, and cell wall materials.
12 . The method of claim 1 , wherein the core material comprises a volatile oil.
13 . The method of claim 1 , wherein the core material comprises one or more flavor components.
14 . The method of claim 1 , wherein the core material is selected from the group consisting of animal oils, vegetable oils, animal protein, vegetable protein, starch, starch derivatives, coffee, tea, vegetable juices, fruit juices, milk protein fractions, eggs, cereal, stevia, animal feed, cocoa powder, vitamins, nutraceuticals, coloring agents, perfumes, fragrances, spices, enzymes, pharmaceutical actives, agricultural actives, pharmaceutically or nutritionally acceptable salts, ceramic materials, catalyst supports, microalgae, hemoglobin, and combinations thereof.
15 . The method of claim 1 , wherein the high-voltage alternating-current source is a high-voltage low-current high frequency alternating-current source.
16 . The method of claim 15 , wherein the high frequency is in the range of about 3 MHZ to about 30 MHz.
17 . The method of claim 1 , wherein the high-voltage alternating-current source is a high-voltage low-current low frequency alternating-current source.
18 . The method of claim 17 , wherein the low frequency is in the range of about 50 kHz to about 3 MHz.
19 . The method of claim 1 , wherein the high-voltage alternating-current source is an electrical resonant transformer circuit.