16 Technology of wafer biscuits

Dr. Sangita Ganguly

1.1 Introduction

Wafers are low-moisture-baked-foods. The primary textural attributes of products, the crunchiness or crispness is highly affected by the product’s physical state (glassy or rubbery). Wafers represent a specialized type of light-textured biscuit, generally made from cereals. The thin, crisp, precisely shaped wafers are available in variety of shapes including flat, hollow, molded cones, rolled cones and sticks. The wafer sheet itself is baked from a simple batter containing little or no sugar. It is a rather tasteless product which has a smooth surface. Wafers usually serve as the edible carriers of an added food. However, the crispness of the wafer enhances the appeal of added food, making the wafer more than an inert carrier. Compared to other biscuits, starch gelatinization in wafer is quite high.

The characteristics of wafer

Wafers are baked in different fancy shapes like cones, sheets, sticks etc. The main features of wafers with respect to other bakery products are:

1. Wafers are very thin biscuits: the thickness lies between 1 and 5 mm.

2. Wafers often have a typical “wafer pattern” on one or both surface of the product. The surfaces are smooth and precisely formed with the dimensions, engravings, logos etc.

3. Wafers are cereal based low fat products. They are made of wheat flour, sometimes with combination of other flours or starches.

4. The product density of wafer ranges from 0.10 to 0.25 g/cm3. The cross-section of product reveals that wafer matrix is highly aerated and primarily composed of gelatinized starch.

5.  Wafers by their delicate crisp texture combine well with different types of coatings and fillings like cream, ice cream, foam etc.

Classification of wafer

Wafers may be classified in two basic types:

• No-or low-sugar wafers
•  High-sugar wafers

Wafer may be following three types:

• Plain
• Sandwiched
• Coated

No-or low-sugar wafers: After baking, these contain from zero to a very low percentage of sucrose or other sugars. The products are of flat and hollow wafer sheets, molded cones, cups, and fancy shapes.

Higher-sugar wafers: This type of product contains over 10% of sucrose or other sugars, which are responsible for the plasticity of the hot, freshly baked sheets. These are formed into different shapes before sugar recrystallization occurs. The products are obtained in rolled sugar cones, rolled wafer sticks or tubes, and deep-formed fancy shapes.

Plain wafers: Plain wafers may be hollow or flat or in any shape desired by the purchaser.

Sandwiched wafers: These types of wafers shall have two or more plain wafers, sandwiched with filling in between. The filling may be cream, jam, jelly, marshmallow, caramel, figs, raisins etc. The fillings shall be not less than 50% by mass of the filled wafer.

Coated wafers: These types of wafers include both half-coated and full-coated wafers. The coating may be of chocolate, substitute fats butter scotch etc. and the fillings shall be not less than 60% by mass of the coated wafers.

Compositional requirement of wafers: The wafers shall comply with the requirements given in Table 1 according to BIS (1988).

Ingredients of wafer biscuits

According to BIS (1988) the ingredients of wafer biscuit preparation can be classified in two types.

Essential ingredients:

The essential ingredients for preparation of batter of wafers are a) Flour and b) Water.

Optional ingredients:

In addition to essential ingredients following ingredients may be added to wafer batter are a) baking powder and other leavening agents, b) cereals, c) chocolate, cocoa powder, coffee extract, d) citric, malic, lactic, tartaric, acetic acid e) food colours, flavouring essences, flavour improvers and fixers f) desiccated coconut, dry fruits and nuts, g) fruit and fruit products, h) salt, dextrose, liquid glucose and sugar products (gur, jiggery etc.), i) emulsifying and stabilizing agents agents, j) preservatives and antioxidents, k) enzymes –fungal alpha amylase for dough conditioning, l) Fat and shortenings, m) malt products, n) milk and milk products,

o)  eggs and egg products, p) spices, condiments and their extracts , q) nutrients-vitamins, minerals etc. and r) yeast.

Wafer oven:

The oven is the heart of the process as it both forms and bakes the wafer. Originally, wafers were made one at a time in hand-held tongs heated over an open fire. The tongs consisted of a pair of strong metal plates which, immediately batter was placed between them, were lached to resist the strong forces. This technique has been mechanized and nearly all wafer ovens still work on this principle producing sheets typically 470×290 mm. Larger sheets are possible but it rarely go above 470×350 mm. The flat wafer sheets have an overall thickness of not more than 2-5 mm. The baking plates can also carry special figures (nuts, sticks, hemispheres, fancy shapes) up to depth of around 20 mm, yielding „hollow wafer sheets‟.

The plate pairs are fixed to heavy carriers which are linked together to form a chain which is circulated continuously through an insulated box (oven). The heavy carriers are required not only support the plates and to keep them rigid, but also maintain their parallel positions against the steam pressures as the baking proceeds. Wafer baking ovens frequently have 32-104 pairs of plates, continuously circulating on a chain. The length of the oven chains and the number of plate pairs has steadily increased so that presently up to 120 plate pairs may form a single plant. However ovens with 41-61 plates are most common. The plates are edged with metal strips to give a closed baking mold, except for small venting channels for steam release.

The plates are heated either directly by gas or by electric heaters and wafer ovens generally operate at temperatures between 160°C and 190°C. The quality of wafer sheets is judged principally by their weight, surface colour and uniformity of moisture content. Texture and crispness tend to be related to one or more of these properties, but basic differences in wafer sheet thickness will affect the internal structure.

Wafer oven maintenance programme is needed periodically to clean the plate surfaces. Deposits of charred oils and sugars build up, blackening the surfaces and causing wafer release problems. Under steady baking conditions with low sugar recipes, cleaning may be needed after about 1000 hours of running. Plate cleaning is best achieved with caustic soda solution. Modern wafer- baking plates often are surface plated, e.g. with chromium for easier release and reduction of cleaning stops.

Role of different ingredients in wafers preparation

Flour:

Gluten strength of flour is a key to finished wafer quality, so selection of flour is also important. Gluten content should be sufficient to provide strength to the wafer without making it too weak and fragile or excessively hard and flinty. Flour milled from soft wheat for biscuit production is preferred for wafer preparation. The medium protein strength (9.5%) flour is usually used for wafer preparation. Flour with protein content between 8.1% and 10.9% gives acceptable wafer sheet. Flours with increased protein content (12.8-13.2%) lead to an unacceptable product.

Flour particle size distribution is also important parameter to produce a high-quality sheet. Flour with smaller particle size gives less dense, soft and friable sheet; course flour gives unacceptable and incomplete sheets.

A few published data are available on wafers made from flours other than wheat flours. However, it is possible theoretically to make wafer from any source of starch, provided the starch is not pre-gelatinized. In wafers there is much more complete gelatinization of the starch as compared to in other biscuits.

The water absorption of flour is important as variation in this property will affect the batter consistency for any given solids content.

Water:

Water is one of the important parameter of wafer sheet preparation. Water is added to produce a convenient consistency and makes the batter pumpable. Water helps in the distribution of ingredients. As a result of evaporation during baking, water also functions as a leavening agent. Wafer formulation should include sufficient water to disperse the ingredients and to obtain a low viscosity to flow over cover plates. Flour and water ratio should be controlled as water levels affect the texture of the sheet. The quantity of water added to wafer batter is roughly 150% of flour weight. Less water decreases the completeness of the sheet; therefore, thick, heavy and unbaked sheets occur. No relationship, still now have been established between wafer quality and hardness of water. The temperature of water alters the viscosity of batter affecting the quality of the sheet. Water temperature should be around 20°C to prevent gluten strand formation. In warm condition, if flour has a high α-amylase activity, viscosity of the batter quickly drops. The unfavourable effect on viscosity could be minimized by using batter within 10-30 min.

Fat and lecithin:

Fat and lecithin are used to help release wafer sheets from plates. There is little or no shortening effect by fats, but microphotographs have revealed that wafer surface is smoother when fats are present in the recipe. Without fats there would be a strong tendency for wafers to stick on the plates. Certain fats are preferred than other for incorporation at the time of mixing. For convenience, liquid vegetable oils are favoured (e.g. groundnut oil, cottonseed oil or sunflower oil). The precaution should be taken to ensure that setting of fat does not occur in the mixer prior to dispersion. Lecithin is a useful addition, it is better to include a fluidized soya lecithin with the fat or oil rather than use powdered lecithin to save cost. Though, the fat content of wafers is low, the inclusion of antioxidant in the oil is necessary to retard rancidity as the surface area of wafer and the internal texture is extremely large.

Egg:

Eggs can serve as a source of both fat and emulsifier (lecithin).

Sugar and milk powder:

They may be added in small quantities to improve quality. The problem associated with these ingredients that both these ingredients promote wafer colouring and sticking to the plates during baking. It is believed, that staling is retarded by incorporation of sugar and crispiness is maintained for longer as the moisture content rises. Sugar, when used in ice cream cones, it is necessary to employ specially designed equipments.

Salt:

Salt is added as a flavour enhancer and the level is usually around 0.25 units per 100 units of flour.

Aeration:

This is most important in wafer preparation. Although bubbles of air are included during batter mixing, most of these float out of the batter before it is deposited onto the plates. If insufficient time is allowed for the bubbles to leave the batter, the density of the batter changes during the course of use ultimately affecting baked sheet weights. Leavening agents help in development of porous texture of wafers by increasing the number of gas cells in batter. Sodium bicarbonate and ammonium bicarbonate or a mixture of two can work to create chemical aeration. Ammonium bicarbonate is particularly effective. Combination of batter consistency and ammonium bicarbonate level is the best way to control batter spread and wafer weight.

Sodium bicarbonate and ammonium-bi-carbonate also affects the final pH and influence the colour development during baking. High pH of batter retards the gluten strands formation which is undesirable.

Yeast is added as a means of aeration. It is most unlikely that any flavour or textural benefits are contributed to the wafer sheet; yeast cells probably form the nuclei for water vapour production which is important for the formation of a good wafer texture. Batter standing times and suitable temperatures to allow multiplication of yeast are not usually very practical, so yeast is now rarely used in batter preparation.

Other ingredients:

The information available about flavouring ingredients of wafer is scanty. Most synthetic flavours and essential oils are prone to steam distillation and hence are lost in wafer production. Protein hydrolysates are fairy heat stable, but they are prone to colour development. Still they may be used for preparation of savoury wafers.

Role of different processing parameter in wafers weight and thickness

The processing parameters that affect wafer sheet weight and thickness has given in Fig. 1 and discussed as below:

Plate gap setting

The thickness of a wafer sheet is determined by the body thickness, related to the gap between the plates and also the depth of the relief or reeding in the plates. The relief cut into the plates gives not only more interest to the appearance of the wafers, but also contributes to their mechanical strength. Thus, any reeding on the top surface should be at 45º to that on the bottom. It is interesting to note that the wafer thickness is not constantly related to the mechanical gap setting between the plates. It is always thicker. The difference is between 19–30% from older slower plants and between 5–13% for newer faster plants.

Volume of batter

The volume is adjusted to just fill the plates allowing a minimum of extrusion through the steam vents. It has been observed that excess deposit gave not only excessive waste but also increased sheet weight.

Batter viscosity

Changes in batter viscosity affect more than one factor. Thick batters have high solids contents and do not flow well on the plates after deposition therefore a high volume has to be applied to achieve a full wafer sheet. This gives a heavier, more dense and harder wafer. The flow of thick batter on a plate can be increased by adding extra ammonium bicarbonate; the gas produced blows the batter to the edges of the plate.

Plate closure speed

Modern plants, operate with very fast latch closure mechanisms for the plates, whereas, the older ovens operated with delayed latching operation. The change in closure speed led to different wafer quality from the same batter. Faster closure gives lower weights and thinner wafers. On some ovens the final locking position of the plates and therefore the closure time can be adjusted slightly.

Steam venting

Large areas for steam venting allow excessive losses of batter but aid in moisture removal. Whereas, small areas control losses and batter spreading better but allow development of excessive pressures. These higher pressures cause increased wear on bearings and set up strains which have bad effects on plate settings.

Baking speed

Baking times vary between 1.5–3 minutes with 2 minutes being about average. On large plants there is a mechanical consideration and it is generally felt that 55 plates per minute is the fastest reasonable speed. Most ovens, even new plants, run at approximately 60% of this speed, that is only 33 plates per minute. Fast baking speeds require high plate temperatures with increased tendency to „shelling‟ (wafers with extremely fragile centre texture) and appreciable moisture gradients across the sheet when they are released. This is because there is not sufficient time for the moisture to move to the steam vents around the edges. The release of the wafers from the plates is affected because some shrinkage occurs after the wafer structure sets and is the result of drying. If the wafer is not sufficiently dried out at the time of plate opening, the shrinkage may not be sufficient to allow the sheet easily to drop away. Conversely, if the drying is too much and some surface burning has occurred sticking may be experienced for this reason also. If the heat disposition across a plate is uneven some cracks may occur in the sheet immediately the plate opens and before the sheet drops away.

Manufacture Technology of wafer biscuits

The ingredients required for preparation of Low-sugar and Higher-sugar wafer batter has listed in Table 3.

Table 3. Waffer batter ingredients (weight parts, flour=100)

Ingredients	Low-sugar wafer	Higher-sugar wafer
Wheat flour	100	100
Water	120-160	100-140
Starch	0-12	0-5
Sucrose	0-4	25-75
Oil/ fat	0.5-2.0	1-6
Milk powder	0-2	0-2
Soy lecithin	0.2-1.0	0.2-1.5
Salt	0-0.6	0-0.6
Sodium bicarbonate	0.1-0.5	0-0.3

Batter preparation

Wafer batters are low viscosity batter prepared from mixing all ingredients. For preparation of wafer batter first, the water-soluble components are dissolved followed by addition of farinaceous ingredients. The batter should be of homogenous nature containing about 35-40% dry matter. Appropriate mixing is necessary for to achieve a homogenous suspension.

Mixing of batter

The aim of the mixing process is to achieve a homogenization of ingredients and hydration of flour. Commercial mixing times range from 2.5 to 6 min. It has been observed that 4 min time is minimum required to achieve homogeneity with a good shear mixer. A high shear mixer is the best as slower mixers may allow gluten stand formation resulting the strings and lumps in the batter. The mixing process should be started as soon as possible after the assembly of all the ingredients. This reduces the possibility of a „dough‟ formation. The use of cold water also reduces the tendency for string formation.

Viscosity of batter

The viscosity of batter should be low enough to flow over and cover the oven plate. The high viscosity results in undesirable quality of wafer. The desirable quality wafers are made from a fluid batter with a viscosity in the range of 300-2000 mPs. It was observed that hard wheat varieties produced batter with stronger rheological properties than soft varieties and the bulk elastic moduli of batter was correlated with hydration of gluten. Greater dominance of elastic properties due to increased dispersion time of gluten led to difficulties in wafer production.

Batter transport and deposition

Immediately after mixing, the batter has much incorporated air, as the air rises out to mix, the batter viscosity reduces. The batter may be slightly lumpy just after preparation due to incomplete mixing. A screen is needed to remove lumps and constant gentle agitation is needed to maintain viscosity of batter. The batter is transferred just after preparation into intermediate tank. The batter is pumped to the oven from the tank via a ring main and spread on to baking plates.

Wafer sheet baking

The baking of wafer sheets is carried out in pairs of cast-iron metal plates with a hinge and latch on opposite sides. Within a few seconds after batter deposition, the baking molds close and locked. At first, the batter is distributed mechanically, but after some time the mold is filled completely by the steam that evolves. A small quantity of batter is extruded as waste through venting channels. The gelatinization of starch starts immediately, the pressurization of mold by steam occurs at right moment, resulting in a well-aerated starch foam.

The glass temperature of wafer matrix rises, when most of the water has been driven off, resulting formation of stable structure. The temperature of wafer increases to 160-190°C. The Maillard reactions take place at this point, resulting typical wafer colour and flavour formation. The baking times are between 1.5 and 2.5 min, depending on the wafer thickness and baking temperature.

During wafer manufacturing process, there is no substantial degradation of starch molecules compared with other bakery products and extruded cereals. Therefore wafers comprise of two unique textural properties:

a) Extreme crispness on biting and initial chewing.

b) Good mouth feeling during prolonged chewing and swallowing owing to the absence of sticky, glutinous stimuli.

Wafer release and cooldown

At the end of the baking operation the plates of the oven open to release the baked sheets. The fresh batter is spread on the plates and reclosed very quickly. The sheets are cooled to room temperature by passing over an arch-type sheet cooler.

Wafer conditioning

Wafers are passed to a conditioning unit, where the moisture content of the sheets is carefully increased so as to achieve some stability in both the texture and size of the wafer. Conditioning is particularly important for wafers that are to be chocolate enrobed. Conditioning usually involves the deliberate addition of moisture to the wafer either by storage in a humid room or by passing the sheets through a high-humidity chamber. In some cases water is actually sprayed onto wafer.

After baking, the residual moisture is 0.8-1.5%. As both the water activity of the air in the production area and the water activity of the air in the production area and the water activity of filling creams or coatings are well above that, wafers pick up moisture very easily. In line with this sorption, the dimensions of the sheet increase by 0.2-0.3% for every 1% of additional moisture. This can result in cracking of the coating in enrobed wafer biscuits. To compensate for low water activity, humidity conditioning up to ~4.5% wafer moisture is possible. This is specially recommended if enrobed or chocolate molded wafer products are made to, to avoid cracking of chocolate during its shelf life. Moreover, with increasing water activity, the wafer texture changes from a soft to a harder crispness, accompanied by a higher mechanical stability, which is good both for handling and for the final product texture. Up to 5-6% moisture content, the wafer sheets keep their typical crisp texture, but higher moisture levels will result in most cases in inadequate, tough, or even soft and soggy textures.

Creaming and Book building

The wafer sheets are passed to the creaming station, where a layer of a sugar-and-fat-based cream is applied to one side. The most common type of cream flavours are chocolate, vanilla, hazelnut, milk, strawberry, and lemon. Creaming is done at temperatures of 30-40°C either by contact spreading with a cream coated roller or by depositing a performed cream film. Bonding between wafers and cream is improved if a warm soft cream is applied rather than cooler stiffer one. As the cream is much softer than biscuit sandwitch cream, handling with pumps and pipes, possibly in a ring main arrangement, is possible.

Coated sheets are built up into piles as desired and a plain topping sheet is added finally. Typically there will be 3 or 4 wafers with 2 or 3 layers of cream respectively in a pile or „book‟. The assembled book must then be pressed together before cooling. For hollow wafers, the cream is added to the hollow parts either by spreading or by controlled single depositing. Two hollow wafer sheets or a hollow and a flat sheet can be combined to form a „book‟.

Cooling and cutting

The wafer books pass into a cooling tunnel to set the cream. The convected cool air can also be applied. The humidity of air should be kept as low as possible to avoid moisture pick-up by the exposed wafers.

The cooled books are cut into eating-size squares, rectangles, fingers, etc. by cutting them in small piles through sets of taut wires, blades or circular saws. There are two cuts at 90° to each other and resulting piles of wafer pieces are ready for packaging, storage or chocolate coating.

Packaging

The wafer biscuits have be to protect against humidity, oxygen and light to prevent oxidative deterioration and to insure a shelf life of 6-9 months. Inadequate packaging-film moisture barriers and bad sealing are the most frequent reasons for latter complaints by customers. Laminated or specially coated films are used for wafer packaging in flow packs, boxes and bags.

Molded Wafer Cones

The molded wafer cones are „hollow‟ wafers in shape of cups and fancy shapes with up to 185 mm in length. They are mainly of two types, a) No-or low-sugar cones, generally known as „cake cones‟ b) molded sugar cones. Low-sugar cones are generally similar to those for sheets and molded sugar cones have an intermediate sugar content, about below 20 parts of sucrose for 100 parts of flour. The traditionally molded a cones have flat tops and regular, symmetric reedings, now a days molds for more sophisticated products are available. The cones and cups with curvilinear tops and artfully designed outsides are available in market in recent times.

The products are produced in cast-iron molds, holds for four to six items are provided in each of these molds, and 12-72 molds are circulated in one oven. The lower part of mold is made of two symmetric halves that open to release the baked pieces. The baked cones are cooled down and stacked for packaging.

Rolled Wafer Cones

‘Rolled sugar cones‟ are the product containing more than 20% concentration of sucrose or other sugars in finished product. The preparation procedure of rolled sugar cone manufacturing are rather similar to no-or low sugat wafer sheet baking with requirement of reduced steam pressure. The deposit is just to form an oval circular sheet. The preparation steps comprise of batter preparation, batter transport and deposition, wafer sheet bakingand wafer take-off, rolling and cone release. After baking, the mold reopens, the sheet is automatically stripped off the plate and rolled immediately on tapered mandrels to form the finished cone. A series of rolling devises mounted on round table operates continuously: sheet removal, rolling, release etc.

Rolled Wafer sticks

Rolled wafer sticks are hollow tubes with walls consisting of very thin multiple layers, similar in texture to crunchy cereals. These layers do not carry a wafer pattern and are ~0.5 mm thick. Rolled wafer sticks have a unique brittle wall texture without being too hard in biting and chewing. The sticks are typical higher-sugar wafers. A strip of batter is applied to a heated drum and baked into a continuous wafer band. The band is rolled immediately while hot into a continuous still formable tube with an internal diameter of ~6-36 mm. From here, a large family of finished product can be created. The tube is automatically cut into wafer stick pieces and cooled. These are consumed as sweet snacks or with ice cream. These can be used as intermediate products of confectionary and other preparations. The tube can be coated inside with compound chocolate or filled partially or fully with chocolate or cream. Cutting and cooldown can be followed by an optional coating or decorating process.

Innovations in wafer-manufacturing equipment

In recent times some new technical concepts have seen in wafer-manufacturing equipment:

1. The oven with vertically stacked baking plates. The floor area requirement is less in this machine. The weight of the stacks eliminates the need for hinges as compared to traditional oven.
2. Rolled wafer stick ovens with “low-emission” heating concept together with a 60% reduction in energy consumption has come into operation. Application of induction heating and replacement of gas-heated drum by a ring is the main key of the instrument. The resultant output is more consistent and controllable product quality with huge reduction in energy consumption for baking.

Further reading

• Dogan IS. 2006. Factors affecting wafer sheet quality. International Journal of Food Science and Technology. 41: 569-576.
• Manley   DJR.   2000.   Technology   of   Biscuits,   crakers   and   Cookies,   3rd   edn.
• Cambridge, UK: Woodheaf Publishing. Pp: 290-306.
• Oliver G. and Sahi SS. 1995. Wafer batters: a rheological study.  Journal of the Science of Food and Agriculture. 67: 221-227.
• Tiefenbacher  K.  F.   1993.  ‘Wafers‟.  in  Encyclopaedia  of  Food  Science,  Food Technology and Nutrition, Academic Press, London. Vol., pp: 417–420.