Detergent additive absorbed into a porous hydrophobic material having a hydrophobic coating

The present invention provides a detergent additive comprising a water-soluble or water-dispersible detergent active compound such as enzyme characterized in that said compound is mixed with a surfactant before absorption into a porous hydrophobic material such as silica, said porous material subsequently being coated with a hydrophobic material such as silicone oil. Detergent compositions containing said additive are also encompassed.

FIELD OF THE INVENTION 
The present invention relates to detergent active compounds and use thereof 
in liquid detergent compositions. More particularly, it relates to 
detergent active compounds having improved storage stability within a full 
detergent composition. 
BACKGROUND OF THE INVENTION 
There are many detergent active materials which require protection from 
atmospheric moisture, air and co-ingredients of compositions with which 
they are formulated. 
Some of these actives include enzymes, bleaches, colourants, catalysts and 
other detergent active compounds. 
For instance, it is well known in the art that enzyme deactivation occurs 
in aqueous detergent compositions containing proteolytic enzymes or 
mixtures of enzymes one of which is proteolytic. 
The loss of detergent activity of said detergent active compounds, also 
referred to as detergent instability has already been retarded by chemical 
stabilization methods. 
Yet the effectiveness of these methods tend to be limited in that different 
chemicals at different levels are needed to protect different detergent 
active compounds. 
Therefore, it is an object of the present invention to provide a 
stabilization system that can be used to protect any detergent active 
compound in any detergent formulation. 
According to the present invention, a detergent additive is provided 
comprising a hydrophillic detergent active compound characterized in that 
said compound is mixed with a surfactant before absorption into a porous 
hydrophobic material, said porous material subsequently being coated with 
a hydrophobic material. 
According to one embodiment, the present invention provides detergent 
compositions comprising detergent active compounds which have improved 
stability upon storage. 
According to another embodiment, the porous hydrophobic material comprising 
a detergent active compound being absorbed into said hydrophobic material 
can be used to store said detergent active compounds in the form of 
non-dusting granulates. 
SUMMARY OF THE INVENTION 
The present invention provides a detergent additive comprising a 
water-soluble or water-dispersible detergent active compound characterized 
in that a mixture of said compound with a surfactant is absorbed into a 
porous hydrophobic material, said porous material being coated with a 
hydrophobic material. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention relates to a stabilization system for detergent 
active compounds having improved storage stability within a full detergent 
composition. 
As utilized herein "stabilization" refers to protecting the detergent 
active compounds by isolating and protecting them from their hostile 
environment upon storage but releasing said compounds during washing 
conditions. 
According to the present invention the detergent active compounds are 
isolated from their hostile environment by reversibly absorbing said 
compounds into a porous hydrophobic material. 
In this way, the porous hydrophobic material serves as a "cage" wherein the 
detergent active compound is enclosed. Subsequently, the pores of the 
detergent additive filled hydrophobic porous material are sealed by 
dispersing said porous material into a hydrophobic liquid. 
By sealing the pores of the hydrophobic material, the hydrophobic liquid 
acts as a "shell", thereby protecting the detergent additive from its 
environment. 
It has now been found that by using the "shell and cage" system of the 
present invention the loss of activity of the detergent active compounds 
is substantially reduced. 
Moreover, it has been found that the protected detergent active compound 
according to the present invention can be readily released under washing 
conditions without losing the ability to perform its normal function. 
More in particular, the present invention provides a detergent additive 
comprising a hydrophillic detergent active compound characterized in that 
said compound is mixed with a surfactant before absorption into a porous 
hydrophobic material, said porous material subsequently being coated with 
a hydrophobic material. 
The present invention also provides a process whereby a detergent active 
compound is reversibly absorbed into particles of a porous hydrophobic 
material, said particles subsequently being dispersed into a hydrophobic 
liquid. 
The detergent active solution 
The detergent active solution comprises a detergent active compound and a 
surfactant. 
Detergent active 
It is widely recognized that the function of a detergent active compound 
can be significantly impaired in detergent compositions by interaction 
between the active compound and other coingredients of the detergent 
composition. For example, detergency enzymes can be affected by 
interaction with other enzymes, bleaches, acids and bases. Perfumes and 
bleaches can be effected by bleach activators. Cationic fabric 
conditioners can be effected by interaction with anionic surfactants; 
organic bleaches can be effected by moisture, metal contamination; 
brighteners/fluorescers can be affected with bleaches. 
The detergent active compounds suitable for the present invention include 
enzymes, bleaches, bleach activators, bleach catalysts, perfumes, 
photoactivators, dyes, brighteners/fluorescers, through the wash 
sanitizers, fabric softening or conditioning agents, hydrolysable 
surfactants, and other detergent active compounds which are water-soluble 
or water-dispersible and mixtures thereof. 
A preferred class of a detergent active compound is a detergency enzyme. 
Examples of enzymes suitable for the present invention are enzymes which 
are active in the removal of soils or stains such as protease, lipase, 
amylase, carboxylase, cellulase, oxidase, peroxidase or mixtures thereof. 
The enzyme may be present in the form of an enzyme solution, e.g. in water 
or a lower water miscible, mono-, di- or polyhydric alcohol such as 
propylene glycol and optionally containing enzyme stabilizers such as is 
known in the art. Enzyme stabilizers which may be present include lower 
alcohols, e.g. glycerol, lower mono- or di- carboxylic acid and their 
salts, especially formates and oxidates, borates and calcium salts. 
Suitable detergent active compounds can also be represented by bleaches, 
bleach activator and bleach catalysts. Suitable inorganic bleaches include 
perborates, percarbonates. Suitable organic bleaches include peroxyacids 
known in art. Suitable bleach precursors are peracetic acid bleach 
precursors such as tetraacetylethylenediamine, triacetin, and acethyl 
trimethyl citrate. 
Other detergent active compounds suitable for the present invention are 
fabric softening or conditioning agents, fluorescers, dyes, 
photoactivators through the wash sanitizers such as phenoxyethanol, and 
other detergent active compounds which are water-soluble or 
water-dispersible and which tend to be unstable upon storage, and mixtures 
thereof. 
Surfactant 
An essential feature of the present invention is that the detergent active 
compound is mixed with a surfactant before being absorbed into the porous 
material. 
Due to the hydrophillic nature of the detergent active suitable for the 
present invention, the detergent active does not spontaneously wet the 
surfaces of the hydrophobic material. It has been found that by adding 
surfactant the detergent active solution is readily absorbed into the 
pores of the hydrophobic material. 
Furthermore, it has been surprisingly found that by adding said surfactant 
to the detergent active the detergent active solution is not immobilized 
onto the hydrophobic material and can be readily desorbed during washing 
conditions. 
The surfactant suitable for the present invention should be compatible with 
the detergent active compound. 
The surfactant to be used for instance, in the case the detergent active is 
an enzyme a surfactant used is preferably a nonionic surfactant. A wide 
range of nonionic surfactants can be used. 
One class of nonionic surfactants useful in the present invention are 
condensates of ethylene oxide with a hydrophobic moiety to provide a 
surfactant having an average hydrophilic-lipophilic balance (HLB) in the 
range from 8 to 17, preferably from 9.5 to 13.5, more preferably from 10 
to 12.5. The hydrophobic (lipophilic) moiety may be aliphatic or aromatic 
in nature and the length of the polyoxyethylene group which is condensed 
with any particular hydrophobic group can be readily adjusted to yield a 
water-soluble compound having the desired degree of balance between 
hydrophilic and hydrophobic elements. 
Especially preferred nonionic surfactants of this type are the C.sub.9 
-C.sub.15 primary alcohol ethoxylates containing 3-8 moles of ethylene 
oxide per mole of alcohol, particularly the C.sub.14 -C.sub.15 primary 
alcohols containing 6-8 moles of ethylene oxide per mole of alcohol and 
the C.sub.12 -C.sub.14 primary alcohols containing 3-5 moles of ethylene 
oxide per mole of alcohol. 
Anionic or cationic surfactants are less likely to be used. However, if the 
absorbed detergent active is unaffected by these surfactants they can 
alternatively be used. 
The level of surfactant used in the present invention should be such to 
ensure sufficient wetting of the hydrophobic material. At high levels of 
surfactant, agglomerates can be formed. Therefore, the level of surfactant 
that can be used should be such to maintain a free flowing hydrophobic 
powder. 
The active-filled porous hydrophobic material may contain additional 
ingredients, which can be premixed with the surfactant before they are 
absorbed into the porous hydrophobic material. These materials include 
other active compounds such as perfumes, brighteners, bleaches, softeners 
and other conventional optional ingredients such as buffers, electrolytes, 
etc. as far as they are chemically compatible with the surfactant active 
solution. 
Porous hydrophobic material 
The surfactant containing detergent active solution is absorbed into the 
pores of the hydrophobic material. 
The porous hydrophobic material suitable for the present invention can be 
any hydrophobic porous material having an average pore diameter larger 
than the size of the molecules that are to be absorbed in the porous 
material. Pore volumes and pore size distributions may be measured by the 
recognized technique of mercury intrusion porosimetry. 
For instance, if the detergent active compound is an enzyme, an average 
pore diameter of the hydrophobic material of 500 angstroms or higher is 
preferred. 
The preferred hydrophobic material that then can be used is silica. The 
average pore diameter of the currently used silica is 1000 .ANG. while the 
absorbed enzyme molecules have diameters in the range of 50 to 150 .ANG.. 
The silica particles can be rendered hyrophobic by treating them with 
dialkylsilane groups and/or trialkylsilane groups either bonded directly 
onto the silica or by means of silicone resin. The silica is further 
characterized by a high absorption value. The absorption can be expressed 
as Dibutylphthalate (DBP) number. Porous silica suitable for the present 
invention is available under the trade name Sipernat.RTM. from Degussa. 
Hydrophobic coating material 
The hydrophobic coating material provides a protective coating for the 
active-filled porous hydrophobic materials herein. 
Coating the pores of the hydrophobic material isolates the detergent active 
compound from environments which causes the degradation of the active 
compounds. 
The active compounds remain in their stabilized material environment 
without interacting with other potentially harmful detergent ingredients 
or the environment is protected from the detergent active compound itself. 
The level of hydrophobic coating material should be such that appropriate 
coverage of all additive-filled porous hydrophobic material is secured. 
The hydrophobic coating material herein is preferably a hydrophobic liquid 
polymer. 
Such a polymer may be an organo polysiloxane oil, e.g. a polydi(alkyl) 
siloxane, especially a polydi(methyl) siloxane. Especially preferred are 
hydrophobic silicone oils which have been proposed for use as antifoam in 
liquid detergents. 
If the detergent active compound is an enzyme, the silicone oil to 
enzyme-filled silica ratio should be at least 1.5:1. 
Alternatively the hydrophobic coating material may be a high molecular 
weight hydrocarbon like petroleum jelly, wax, or water insoluble but water 
permeable polymeric material such as carboxymethylcellulose, polyvinyl 
alcohol, polyvinyl pyrrolidone or polycaprolactone. 
Detergent ingredients 
In another embodiment of the present invention, detergent compositions are 
provided, comprising the detergent active composition of the present 
invention, and further comprising detergent ingredients. Detergent 
compositions within the meaning herein, include laundry detergent 
compositions, dishwashing compositions or hard surface cleaning 
compositions. Detergent ingredients include surfactants, builders and 
optional detergent additives. A wide range of surfactants can be used in 
the detergent composition of the present invention. 
A typical listing of anionic, nonionic, ampholytic and zwitterionic 
classes, and species of these surfactants, is given in U.S. Pat. No. 
3,664,961 issued to Norris on May 23, 1972. 
Mixtures of anionic surfactants are particularly suitable herein, 
especially mixtures of sulphonate and sulphate surfactants in a weight 
ratio of from 5:1 to 1:2, preferably from 3:1 to 2:3, more preferably from 
3:1 to 1:1. Preferred sulphonates include alkyl benzene sulphonates having 
from 9 to 15, especially 11 to 13 carbon atoms in the alkyl radical, and 
alpha-sulphonated methyl fatty acid esters in which the fatty acid is 
derived from a C.sub.12 -C.sub.18 fatty source preferably from a C.sub.16 
-C.sub.18 fatty source. In each instance the cation is an alkali metal, 
preferably sodium. Preferred sulphate surfactants are alkyl sulphates 
having from 12 to 18 carbon atoms in the alkyl radical, optionally in 
admixture with ethoxy sulphates having from 10 to 20, preferably 10 to 16 
carbon atoms in the alkyl radical and an average degree of ethoxylation of 
1 to 6. Examples of preferred alkyl sulphates herein are tallow alkyl 
sulphate, coconut alkyl sulphate, and C.sub.14-15 alkyl sulphates. The 
cation in each instance is again an alkali metal cation, preferably 
sodium. 
One class of nonionic surfactants useful in the present invention are 
condensates of ethylene oxide with a hydrophobic moiety to provide a 
surfactant having an average hydrophilic-lipophilic from 9.5 to 13.5, more 
preferably from 10 to 12.5. The hydrophobic (lipophilic) moiety may be 
aliphatic or aromatic in nature and the length of the polyoxyethylene 
group which is condensed with any particular hydrophobic group can be 
readily adjusted to yield a water-soluble compound having the desired 
degree of balance between hydrophilic and hydrophobic elements. 
Especially preferred nonionic surfactants of this type are the C.sub.9 
-C.sub.15 primary alcohol ethoxylates containing 3-8 moles of ethylene 
oxide per mole of alcohol, particularly the C.sub.14 -C.sub.15 primary 
alcohols containing 6-8 moles of ethylene oxide per mole of alcohol and 
the C.sub.12 -C.sub.14 primary alcohols containing 3-5 moles of ethylene 
oxide per mole of alcohol. 
Another class of nonionic surfactants comprises alkyl polyglucoside 
compounds of general formula 
EQU RO (C.sub.n H.sub.2n O) t.sup.Z x 
wherein Z is a moiety derived from glucose; R is a saturated hydrophobic 
alkyl group that contains from 12 to 18 carbon atoms; t is from 0 to 10 
and n is 2 or 3; x is from 1.3 to 4, the compounds including less than 10% 
unreacted fatty alcohol and less than 50% short chain alkyl 
polyglucosides. Compounds of this type and their use in detergent are 
disclosed in EP-B 0 070 077, 0 075 996 and 0 094 118. 
Also suitable as nonionic surfactants are poly hydroxy fatty acid amide 
surfactants of the formula 
##STR1## 
wherein R.sup.1 is H, or R.sup.1 is C.sub.1-4 hydrocarbyl, 2-hydroxy 
ethyl, 2-hydroxy propyl or a mixture thereof, R.sup.2 is C.sub.5-31 
hydrocarbyl and Z is a polyhydroxyhydrocarbyl having a linear hydrocarbyl 
chain with at least 3 hydroxyls directly connected to the chain, or an 
alkoxylated derivative thereof. Preferably, R.sup.1 is methyl, R.sup.2 is 
a straight C.sub.11-15 alkyl or alkenyl chain such as coconut alkyl or 
mixtures thereof, and Z is derived from a reducing sugar such as glucose, 
fructose, maltose, lactose, in a reductive amination reaction. 
The compositions according to the present invention may further comprise a 
builder system. Any conventional builder system is suitable for use herein 
including aluminosilicate materials, silicates, polycarboxylates and fatty 
acids, materials such as ethylenediamine tetraacetate, metal ion 
sequestrants such as aminopolyphosphonates, particularly ethylenediamine 
tetramethylene phosphonic acid and diethylene triamine 
pentamethylenephosphonic acid. Though less preferred for obvious 
environmental reasons, phosphate builders can also be used herein. 
Suitable builders can be an inorganic ion exchange material, commonly an 
inorganic hydrated aluminosilicate material, more particularly a hydrated 
synthetic zeolite such as hydrated zeolite A, X, B or HS. 
Another suitable inorganic builder material is layered silicate, e.g. SKS-6 
(Hoechst). SKS-6 is a crystalline layered silicate consisting of sodium 
silicate (Na.sub.2 Si.sub.2 O.sub.5). 
Suitable polycarboxylates builders for use herein include citric acid, 
preferably in the form of a water-soluble salt, derivatives of succinic 
acid of the formula R--CH(COOH)CH2(COOH) wherein R is C10-20 alkyl or 
alkenyl, preferably C12-16, or wherein R can be substituted with hydroxyl, 
sulfo sulfoxyl or sulfone substituents. Specific examples include lauryl 
succinate , myristyl succinate, palmityl succinate2-dodecenylsuccinate, 
2-tetradecenyl succinate. Succinate builders are preferably used in the 
form of their water-soluble salts, including sodium, potassium, ammonium 
and alkanolammonium salts. 
Other suitable polycarboxylates are oxodisuccinates and mixtures of 
tartrate monosuccinic and tartrate disuccinic acid such as described in 
U.S. Pat. No. 4,663,071. 
Especially suitable fatty acid builders for use herein are saturated or 
unsaturated C10-18 fatty acids, as well as the corresponding soaps. 
Preferred saturated species have from 12 to 16 carbon atoms in the alkyl 
chain. The preferred unsaturated fatty acid is oleic acid. Another 
preferred builder system for liquid compositions is based on dodecenyl 
succinic acid. 
Other suitable water-soluble organic salts are the homo- or copolymeric 
acids or their salts, in which the polycarboxylic acid comprises at least 
two carboxyl radicals separated from each other by not more than two 
carbon atoms. 
Polymers of this type are disclosed in GB-A-1,596,756. Examples of such 
salts are polyacrylates of MW 2000-5000 and their copolymers with maleic 
anhydride, such copolymers having a molecular weight of from 20,000 to 
70,000, especially about 40,000. 
In laundry detergent compositions detergency builder salts are normally 
included in amounts of from 10% to 80% by weight of the composition 
preferably from 20% to 70% and most usually from 30% to 60% by weight. 
Other components used in detergent compositions may be employed, such 
enzymes and stabilizers or activators therefore, soil-suspending agents, 
soil-release agents, optical brighteners, abrasives, bactericides, tarnish 
inhibitors, coloring agents, and perfumes. 
The laundry detergent compositions according to the present invention can 
be in the liquid form and in particular in "compact form"; in such case, 
the liquid detergent compositions according to the present invention will 
contain a lower amount of water, compared to conventional liquid 
detergents. The detergent additive in liquid form according to the present 
invention will typically be emulsified in said liquid detergent 
composition. 
The laundry detergent compositions according to the present invention can 
be in granular form and incorporate a builder salt. Granular compositions 
according to the present invention can also be in in "compact form"; i.e. 
they may have a relatively higher density than conventional granular 
detergent compositions according to the present invention will contain a 
lower amount of "inorganic filler salt", compared to conventional granular 
detergents; typical filler salts are alkaline earth metal salts of 
sulphates and chlorides, typically sodium sulphate; "compact" detergents 
typically comprise not more than 10% filler salt. 
The detergent additives herein in liquid form will typically be sprayed 
onto the granules of said detergent compositions. 
Liquid dishwashing compositions according to the present invention 
typically contains an enzyme or a mixture of enzymes as the protected 
detergent active. 
Liquid dishwashing compositions, and hard surface cleaning compositions are 
described in, resp., International Applications WO 92/06171 and EP-A- 428 
816.

The following examples illustrate the present invention and the improved 
stability of detergent actives obtained therefrom. 
More in particular, these examples illustrate the benefits of the present 
invention if enzymes are used as a detergent active. 
EXAMPLE I 
A detergent additive according to the present invention is processed by 
adsorbing the enzyme solution into the pores of hydrophobic silica which 
is then dispersed in silicone oil. In order to provide a detergent 
composition comprising the detergent additive of the present invention, 
the silicone oil dispersion is finally dispersed in the liquid detergent 
matrix. The process encompasses the following steps and is exemplified 
with silica as a porous hydrophobic material and silica oil as a 
hydrophobic protective coating layer: 
1. Non-ionic surfactant (alkyl alcohol ethylene oxide condensate with an 
average of 7 ethoxylate units and an alkyl chain length of 13 to 15 carbon 
atoms having a HLB-value of 9 to 13) is added at approximately 3 to 5% by 
weight in the raw enzyme solution. 
2. The surfactant containing enzyme solution is then combined with porous 
hydrophobic silica (currently used Sipernat D10 ex Degussa) at ratio 2.5 
times the silica's weight (corresponding to the silica's total pore 
volume). The enzyme solution is added in a dropwise manner under stirring 
(no more than 1000 rpms to aid the production of a homogeneously enzyme 
filled silica). At this stage the product is still in powder form. A 
variant of this step includes the addition of 5% of hydrophobic silica 
Aerosil R972 ex Degussa after the enzyme adsorption has occured. 
3. This powder is subsequently dispersed in silicone oil 
(polydimethylsiloxane). We have currently experimented with silicone oils 
with viscosities of 500, 1000, 5000, 12500 and 30000 cs. Dispersion occurs 
under continuous stirring with a propeller mixer at 1600 to 1850 rpm for 
about 3 minutes. 
4. The silicone oil dispersion is finally emulsified in the detergent 
matrix by techniques known in art. 
EXAMPLE II 
Selection of the hydrophobic porous material 
The porous hydrophobic material suitable for the present invention has a 
high absorption value and an average pore diameter larger than the average 
enzyme molecular size. 
Porous silica corresponding to the above specification available under the 
trade name Sipernat.sup..RTM. from Degussa is used. Based on DBP (Dibutyl 
Phthalate) absorption data for Sipernat.sup.200 D10 (2.4 g DBP absorbed/g 
of silica) and DBP's density (=1.0484 cm.sup.3 /g), the total pore volume 
per gram of silica is calculated. 
Pore Volume (PV) =2.289 cm.sup.3 /g of silica The average pore diameter is 
given by the empirical equation: 
##EQU1## 
where S is the specific surface area of Sipernat D10(=90 m2/g). Since the 
average enzyme molecular diameter does not exceed approximately 150 .ANG. 
there is no hindrance. 
EXAMPLE III 
The following detergent compositions are prepared, all based on a liquid 
detergent composition. Such a liquid detergent composition typically 
contains the following ingredients: 
TABLE I 
______________________________________ 
% by weight of the total detergent composition 
I II 
______________________________________ 
Linear alkylbenzene sulfonate 
10 15 
Alkyl sulphate 4 
Fatty alcohol (C.sub.12 -C.sub.15) ethoxylate 
9 14 
Fatty acid 5 10 
Oleic acid 4 
Citric acid 5 9 
KOH 3 
NaOH 5.4 
Monoethanolamine 9 
Propanediol 1.5 9 
Ethanol 5 1 
Minors up to 100 
______________________________________ 
The stability of protected enzymes according to the present invention is 
demonstrated by storage tests. The storage stability of the "caged" enzyme 
formulated in a detergent compositions is compared versus the stability of 
a "free" (not encaged) enzyme. 
The extent of the enzyme release and the activity of the released enzyme 
was measured in the presence of other enzymes, More in particular, the 
stability of caged and free cellulase was determined in the presence of 
Savinase. The liquid detergent composition of Table I was supplemented as 
indicated below: 
I) 0.2% Savinase (16KNPU/g) caged cellulase having a composition as 
indicated below: 
__________________________________________________________________________ 
silica/cellulase 
Silica Cellulase solution 
ratio sil./cell.. 
extra addition 
amount 
sil. oil 200 fluid 
amount 
__________________________________________________________________________ 
Sipernat D10 
+3% NIAO.sub.7 
1:2.5 5% Aerosil R972 
10 g 
1000 cs 30 g 
__________________________________________________________________________ 
II) 0.2% Savinase (16KNPU/g) Free cellulase 
The samples containing caged cellulase-solution were processed according to 
Example I. 
The samples were stored at 35.degree. C. and analyzed for residual 
cellulase activity at the end of 1 week of storage. 
The cellulase activity was determined indirectly by Launderometer tests. 
The degree of depilling of the fabrics was visually observed. 
Test procedure: 0.5 kg of fabric laundry load was washed in a launderometer 
at 40.degree. C. The hardness of the water was 2.5 mM Calcium and the 
composition concentration was 0.8% in the wash liquor. For depilling 
evaluation swatches of worn cotton fabrics were dried in a tumble-dryer 
for 30 minutes prior to assessment of the depilling performance. 
Comparative depilling assessment was done by expert judges using a 
reference, the reference being worn cotton fabrics washed in the presence 
of fresh added cellulase and no Savinase. Depilling was assessed after two 
washcycles of three hours. 
First a calibration curve was graded in order to correlate the level of 
cellulase with the softening performance. 
Then the swatches were washed with the samples containing caged cellulase 
and with samples containing free cellulase and the softness performance 
was assessed of both samples. 
Then the cellulase residual activity of both samples was determined by the 
calibration curve. The results are shown in the following table with 
activity expressed as a percentage of the initial activity of that 
formulation. Results: 
______________________________________ 
Sample 1 wk, 35.degree. C. 
______________________________________ 
Free cellulase 0 
caged cellulase 
75 
______________________________________ 
The samples containing caged cellulase according to the present invention 
are found to exhibit substantially improved retention of enzyme activity 
compared with samples containing free enzyme in the presence of Savinase.