Oil-in-water emulsion glazing agent for foodstuffs

A glazing agent for bakery products comprises a homogenized emulsion of 10-50 wt. % of an edible oil (e.g. soybean oil), 5-15 wt. % (of the aqueous phase) of a protein (e.g. sodium caseinate), 2-10 wt. % of a thin-boiling starch (e.g. a dextrin) and water. Optionally an emulsifier like lecithin can xanthan gum is being used. The emulsion may be spray-dried.

The present invention relates to a glazing agent for bakery products such 
as bread, bread-rolls, biscuits and the like. 
It is known that gloss can be imparted to the surface of baked goods by 
brushing the baked goods, at the place where this gloss is desired, with 
lightly beaten egg before baking. Indeed, such a glazing agent yields a 
reasonably well adhering, shiny coating, but the disadvantage thereof is 
that this agent is expensive, which makes use on industrial scale 
unattractive. Moreover, the agent has bad keeping qualities. 
From experiments it has now appeared that an excellent glazing agent for 
bakery products can be obtained by providing this agent in the form of a 
homogenized emulsion of a protein, an edible oil, water and a thin-boiling 
starch. The homogenized emulsion can be dried and, before use, the dried, 
homogenized emulsion may be reconstituted with water. 
The requirements for a good glazing agent are manifold. On the one hand, 
good optical properties should be imparted to the baked goods, owing to 
the glazing agent being present in a smooth, shiny, homogeneous layer on 
the baked goods. On the other hand the agent must be readily applicable 
and therefore its rheological properties should be favourable. Lastly, the 
agent should be suitable for processing on a large industrial scale, in 
which the microbiological keepability also plays a great role. 
With respect to the rheological properties, it has appeared from 
experiments that the viscosity of the glazing agent is an important 
property. If the viscosity of the emulsion is too low, the danger exists 
that the agent tends to form islands or droplets on the goods to be baked, 
so that, after baking, no firm, shiny, homogeneous film is obtained. 
Moreover, with a low-viscosity emulsion the solids content is generally 
too low, so that too much glazing agent has to be applied in order still 
to obtain sufficient film on the baked goods after baking. 
When the viscosity is too high, the glazing agent cannot be applied readily 
to the goods to be baked and, moreover, the thickness of the film cannot 
be controlled well and the optical properties of the films are clearly 
worse (e.g. less gloss). Besides that, the danger of skin formation 
exists, i.e. that the glaze layer becomes detached locally or completely 
from the baked goods. 
The amount of oil used in the emulsion is important for the flexibility of 
the film obtained after baking. It has appeared that, when the glazing 
agent is used in the form of an emulsion, even with prolonged storage at 
5.degree. C., when the upper layer of the baked goods is already becoming 
soft, yet the glaze layer still remains of visually good quality. 
The stability of the emulsion is related to the particle size of the 
emulsion, with small particles indeed quickly giving rise to a high 
viscosity, but, on the other hand, leading to a stable emulsion. The 
particle size of the emulsion is also determined by the amount and the 
type of a possibly used emulsifier, such as e.g. lecithin. 
Finally, it has appeared that the stability and the viscosity of the 
emulsion can also be influenced by the addition of xanthan gum. By this 
addition, thixotropic properties are imparted to the emulsion, which 
prevent the emulsion from dripping off when used on curved surfaces. 
When the glazing agent, upon heating on the surface of the baked goods, 
becomes brown too quickly, indeed a smooth and shiny layer is obtained in 
an early stage of the baking process, but the baked goods have not yet 
been sufficiently well baked and the further heating necessary for this 
then leads to deterioration of the quality of the glaze layer. Therefore a 
good balance should be found between the browing speed of the glazing 
agent on the one hand and, on the other hand, the baking speed of the 
goods to be baked. 
It has now been found, that a good glazing agent for bakery products, 
meeting the requirements mentioned above, consists of a homogenized 
emulsion of a protein, an edible oil, water and a thin-boiling starch. 
preferably the homogenized emulsion is of the oil-in-water (O/W) type and 
it consists of sodium caseinate, an edible oil, water and a roasted 
dextrin starch. 
Hence the present invention relates to a glazing agent for bakery products, 
which is characterized in that it consists of a homogenized emulsion of a 
protein, an edible oil, water and a thin-boiling starch. Preferably the 
homogenized emulsion comprises 10 to 50% by weight (calculated on the 
total emulsion) of an edible oil, from 2 to 10% by weight (calculated on 
the total emulsion) of a thin-boiling starch, from 5 to 15% by weight 
(calculated on the weight of the aqueous phase) of a protein, the 
remainder of the emulsion being water, and the weight ratio between the 
oil phase and the aqueous phase being from 1:1 to 1:9. Particularly good 
results were obtained with a glazing agent consisting of a dispersion of 
from 8 to 12% by weight (calculated on the weight of the aqueous phase) of 
a protein, from 25 to 35% by weight (calculated on the total emulsion) of 
an edible oil from 3 to 5% by weight (calculated on the total emulsion) of 
a thin-boiling starch, the remainder of the emulsion being water, and the 
weight ratio between the aqueous phase and the oil phase being (1-4):1. 
In U.S. Pat. No. 3,323,922 (The Pillsbury Comp.) a coating agent is 
described that can also be used for the coating of foodstuffs and that 
consists of three components, namely a film-forming substance (such as 
e.g. sodium caseinate), a plasticizer for this film-forming substance 
(such as e.g. water) and a substance which is liquid at the temperature at 
which the coating is formed and which is immiscible with the plasticizer 
(e.g. an edible oil or fat). In the examples of this patent specification, 
a system of sodium caseinate, water and soybean oil is described. In this 
patent specification however, it is nowhere mentioned or even suggested 
that this coating agent would be a good glazing agent. On the contrary, it 
is observed that the excess plasticizer is removed by applying a drying 
treatment after the coating of the product, in which the temperature 
should be kept below the boiling point of the plasticizer (thus, in the 
case of water, below 100.degree. C.). Moreover, the purpose of the coating 
agent is that it protects the product lying under it against the effects 
of the atmosphere, and for this purpose this coating agent should lead 
primarily to a well closed film on the product. The film of a glazing 
agent, however, should not be closed, because the vapour formed during 
baking must be able to escape. 
The terms "oil" and "fat" are used as synonyms in this description and the 
claims. The term "oil" relates to mixtures of glycerides, which are liquid 
at room temperature (18.degree. C.). Such oils can be single oils, but 
also mixtures of different kinds of oils and/or fat fractions. The oils 
may have been subjected to various treatments, such as partial 
hydrogenation, interesterification and the like, and combinations of these 
treatments. Examples of suitable oils are soybean oil, sunflower oil and 
maize oil. 
The protein used is preferably sodium caseinate, but also other proteins, 
which yield stable dispersions in combination with the remaining 
components of the glazing agent can be used, such as soya protein, blood 
protein, proteins obtained with the aid of microorganisms, partial 
hydrolysates of proteins and mixtures of these proteins. 
The thin-boiling starch is preferably a dextrin and, as such, "Crystal Gum" 
(Trade-name; a tapioca dextrin ex National Starch Corp.) has appeared to 
be very effective. But also thin-boiling, modified potato starches and 
thin-boiling corn starches may be used. 
In the preparation of the oil-in-water emulsion it has appeared to be 
effective to use an emulsifier, for example lecithin, in an amount of 0.5 
to 1% by weight, preferably about 0.7% by weight (calculated on the total 
emulsion). When xanthan gum is used as an emulsion stabilizer, it is used, 
depending on the desired viscosity, in an amount of up to about 0.25% by 
weight (calculated on the total emulsion). In practice it has appeared 
that the glaze emulsion preferably has a dynamic viscosity of 150 to 400 
mPas. The viscosity employed is partly determined by the technique used 
for applying the glazing agent. At this viscosity the emulsion can also be 
used on industrial scale and it is applied to the goods to be baked, 
preferably by spraying or atomizing, in an amount of about 30 to 70 
mg/cm.sup.2. The glazing agent according to the invention can also be 
applied to the goods to be baked by other means than spraying. Moreover, 
it can be applied shortly or just before baking, but it can also be 
applied to dough products which are subsequently deep-frozen, then thawed 
and finally baked. 
The present invention also relates to a process for the preparation of a 
glazing agent according to the invention. 
In a first process, the protein is mixed with the thin-boiling starch and 
this mixture is kneaded with a portion of the water to a paste which is 
allowed to stand for one night at 5.degree. C. Subsequently the rest of 
the water, which has been heated to 75.degree. C., is stirred together 
with the paste until all lumps have disappeared. The edible oil (possibly 
mixed with the emulsifier) is then added to the slurry thus obtained, with 
intensive stirring for 15-30 minutes. The emulsion obtained is then 
homogenized under pressure (e.g. 200 bar). 
In a modification of this process, the thin-boiling starch is first boiled 
with an amount of water such that an approximately 25 wt.% solution in 
water is obtained, whereafter this solution is mixed with the paste of the 
protein and another portion of the water, until all lumps has disappeared. 
Thereafter, with very intensive mixing, the edible oil (possibly mixed 
with the emulsifier) is added, whereafter the emulsion obtained is 
homogenized under pressure. 
In a second process according to the present invention, the glazing agent 
is obtained by dispersing the sodium caseinate together with the 
thin-boiling starch in the edible oil (in which the optional emulsifier 
has been dissolved), whereafter the slurry obtained is mixed, while 
stirring, with hot water (heated to about 75.degree. C.). Finally, the 
emulsion is cooled to about 30.degree. C. and homogenized at a pressure 
of, for example, 200 bar. 
From tests, it has appeared that if the thin-boiling starch as such as used 
as glazing agent, it yielded a glaze layer that was too hard and lacked 
flexibility and that, as a result of mechanical handling of the baked 
goods, such as e.g. the packaging thereof, quickly became detached from 
baked goods. In combination with the other components of the glazing agent 
according to the present invention, however, the thin-boiling starch 
appeared to be an excellent viscosity regulator, which substantially 
contributed to the smoothness of the surface and which also brought about 
a good balance between the browning speed of the glazing agent and the 
baking speed of the goods to be baked. 
It has also appeared that it is possible to dry the oil-in-water emulsion, 
preferably by spray-drying. In spite of the high oil content of the 
glazing agent, a non-sticky, free-flowing powder is obtained that can be 
rehydrated to an oil-in-water emulsion both with cold and with hot water. 
The advantage of this embodiment of the invention is that in this way the 
glazing agent can be provided in a form with good keepability, which is of 
great importance particularly for use on industrial scale. 
The invention will now be further explained with the help of the following 
non-limiting examples.

EXAMPLE I 
6.3% by weight (calculated on the total emulsion) of sodium caseinate was 
mixed with 5.0% by weight of "Crystal Gum" (Trade-name; ex National Starch 
Corp.), whereafter 30.0% by weight of soybean oil mixed with 0.7% by 
weight of lecithin (both amounts calculated on the total emulsion) heated 
to 75.degree. C. were mixed with the mixture of sodium caseinate and 
"Crystal Gum" to a homogeneous slurry. Subsequently, with intensive 
stirring, this slurry was mixed with 58% by weight of water of 80.degree. 
C. (calculated on the total emulsion). The emulsion obtained was cooled 
and homogenized at 200 bar. 
The emulsion was sprayed onto the lids of meat pies in an amount of 30 to 
60 mg/cm.sup.2, whereafter the pies were baked in an oven with forced air 
current for 20-25 min. at 220.degree. C. 
Meat pies were obtained with an attractive, smooth homogeneous film, which 
had an excellent gloss. 
EXAMPLE II 
With the aid of a kneading machine, a paste was formed from 6.3% by weight 
(calculated on the total emulsion) of sodium caseinate and 11.6% by weight 
(calculated on the total emulsion) of water. This paste was allowed to 
stand for one night at 5.degree. C. 
Subsequently a 25 wt.% solution of "Crystal Gum" (Trade-name; ex National 
Starch Corp.) in water was prepared by boiling the appropriate amount of 
"Crystal Gum" in water. The solution was cooled to room temperature and an 
amount of it, such that in total 5.0% by weight of "Crystal Gum" 
(calculated on the total emulsion) was added, was mixed with the paste of 
the sodium caseinate. Stirring was carried out until all lumps had 
disappeared. Finally, under very vigorous stirring, 30.0% by weight of 
soybean oil mixed with 0.7% by weight of lecithin (both calculated on the 
total emulsion) was added to the slurry of sodium caseinate and "Crystal 
Gum", after which stirring was carried out for a further 30 minutes and 
the emulsion obtained was subsequently homogenized at 200 bar. 
The emulsion was applied to puff-pastry biscuits in an amount of about 50 
mg/cm.sup.2, whereafter they were baked in an oven with forced air current 
for 20 min. at 220.degree. C. 
EXAMPLE III 
With the aid of a powder mixer, a homogeneous mixture was made of 6.3% by 
weight of sodium caseinate, 5.0% by weight of thin-boiling starch 
("Crystal-Gum"; Trade-name; ex National Starch Corp.), 0.2% by weight of 
common salt and 0.1% by weight of xanthan gum (all amounts calculated on 
the total emulsion). 
This powdery mixture was added at 30.degree. C., with stirring, to 35% by 
weight soybean oil (calculated on the total emulsion) to which 0.7% by 
weight of soya lecithin (calculated on the total emulsion) had been added 
beforehand. After the slurry had been homogeneously distributed, water of 
80.degree. C. was added under stirring, and in an amount of 100% by weight 
calculated on the emulsion. 
After being stirred for about 15 minutes, the mixture was homogenized at a 
temperature of 65.degree. C. and subsequently the emulsion was pasteurised 
for 20 sec. at 80.degree. C. in a plate heat exchanger and finally cooled 
to 10.degree. C. 
After storage for 14 hours at 10.degree. C. the emulsion was sprayed onto 
splices of puff pastry with the aid of a high pressure spraying pistol, 
which slices were subsequently baked for 20 minutes at 220.degree. C. 
After application and before and during the baking, the glazing agent 
displayed no tendency towards dripping off or to island or droplet 
formation. 
After baking, the glaze formed a smooth, closed, glossy layer on the puffy 
pastry. 
EXAMPLES IV-VII 
With the aid of a powder mixer, a homogeneous mixture was made of the 
sodium caseinate, the thin-boiling starch, the common salt and the xanthan 
gum in the amounts as indicated in Table I (all amounts calculated on the 
total emulsion). 
The powdery mixture obtained was added with stirring to the soybean oil (at 
70.degree. C.) to which the soya lecithin had been added while stirring at 
70.degree. C. After the slurry had been homogeneously distributed, water 
of 70.degree. C. was added under stirring, and, after being stirred for 15 
minutes, the mixture was homogenized at a temperature of 65.degree. C. and 
subsequently the emulsion was pasteurised for 20 sec. at 80.degree. C. in 
a plate heat exchanger and finally cooled to 10.degree. C. 
TABLE I 
______________________________________ 
Example IV V VI VII 
______________________________________ 
Soybean oil 30.0% 30.0% 30.0% 30.0% 
Sodium caseinate 
6.3% 6.3% 6.3% 6.3% 
Crystal Gum 5.0% -- -- -- 
Soya lecithin 
0.7% 0.7% 0.7% 0.7% 
Xanthan gum 0.05% 0.05% 0.05% 0.05% 
Sodium chloride 
0.1% 0.1% 0.1% 0.1% 
Water 57.85% 57.85% 57.85% 57.85% 
Mor Sweet 01924.sup.(1) 
-- 5.0% -- -- 
Perfactamyl gel.sup.(2) 
-- -- 5.0% -- 
Perfactamyl gel 45.sup.(3) 
-- -- -- 5.0% 
______________________________________ 
All percentages are weight percentages, based on the final emulsion. 
.sup.(1) A hydrolysate, obtained by acid hydrolysis of corn starch, ex 
CPC; Trade Mark. 
.sup.(2) An oxidised potato starch, ex Avebe, The Netherlands; Trade Mark 
.sup.(3) A starch acetate, ex Avebe, The Netherlands; Trade Mark. 
The final emulsion in all examples was sprayed onto slices of puff pastry 
with the aid of a high pressure spraying pistol in a thickness of 2 mm, 
after which the slices were baked for 15 minutes at 210.degree. C. In 
Examples VI and VII 75 grams of the total emulsion were diluted with 25 
grams of water before being sprayed onto the puff pastry. 
After baking, the glaze formed a smooth, closed, glossy layer on the puff 
party.