COMMON FORMS OF CHOCOLATE AND THEIR COMPOSITION:

In its simplest form, chocolate is a combination of sugar and processed cocoa beans, including both cocoa solids and the lipid fraction known as cocoa butter. In this form, it is sometimes referred to as plain chocolate but is commonly known as dark chocolate. Incorporating dried milk (both milk solids and milkfat) produces the obvious result:milk chocolate. A combination of sugar, dried milk and cocoa butter with cocoa solids omitted yields what is commonly called white chocolate. In most countries with moderate to high chocolate consumption, regulating bodies or agencies set minimum standards or rangers for the major ingredients in all three of these forms of chocolate, allowing minor additions of a limited set of other ingridients. A notable exception is white chocolate in the United States, which doesn’t currently have a standard for white chocolate. Combinations of cocoa solids, cocoa butter, suger or dried milk which contain non-standard ingredients or contain standard ingredients at non-standard levels, cannot be labeled and sold as chocolates and are generally called confectionner’s compounds or other similar designation. As we will see, these standarts will have consequences for the shelf life of chocolates since they restrict the addition ingredients which might be intended to enhance shelf life.

TABLE
Typical Formulae for Chocolates


Total fat content will vary with formulation, source of ingredients, etc., but for dark, milk and white chocolates alike, the value will be somewhere in the vicinty of 30%;this includes Total fat content will vary with formulation, source of ingredients, etc.,but for dark milk the cocoa butter from lıquor, added cocoa butter and milkfat. With sugar ingredıated at nearly 50% plus milk sugars (lactose),it is obvious that chocolates are mostly fats and sugars, so stability or changes in these components during manufacture and storage will have great influence on shelf life.

SOLID CHOCOLATE: LOW IN WATER, HIGHLY STABLE:

Literature on the shelf life of chocolate is somewhat sparse. This is probably due in part to the fact that solid chocolate, by itself, is quıte stable compared to other processed food pruducts. Solid dark chocolate, if processed properly and stored under reasonable and stable environmental conditions,can be expected to have a shelf life of at least one year. Solid milk chocolate can be slightly more susceptible to certain types of storage defects but with appropriate processing, packaging and storage, its shelf life may not be inferior to that of a comparable dark chocolate. One reason for the relative stability of solid chocolate is that it contains very little water, as little as 0.1% to 1.0% in dark chocolates and 5% to 1.5% in milk chocolates. Drying roasting and grinding cocoa beans leave only 2-3.5 % water in chocolate liquor. Pre-drying milk or crumb drying along with conching and other processing steps remove most of the moisture which might be contributed by other ingredients, principally the milk in milk chocolate. The resulting low level of water minimizes the opportunity for fungal growth, although it can occur if the product is stored in high humidity with little or no moisture resistant wrapping. On the other hand, with an Equilibrium Relative Humidity (ERH) of 20-35%, i.e.water activity (aw ) of .20 to .35, chocolates will slowly absorb moisture from virtually any atmosphere. This will eventually affect eating quality as the chocolate becomes “chewy”, “gummy”or even “waxy” in texture rather than demonstrating its usual meltaway and creaminess. Fortunately, this will happen so slowly that it should not compromise th approximate one year shelf life of solid chocolates as long as reasonably moisture-resistant wrapping or foiling is employed and extended exposure to high humidity does not occur. Except under fairly severe conditions, a totally heat sealed, high barrier package is not necessary.

OTHER STORAGE CONSIDERATIONS:
Infestation:

Chocolate is highly desirable food, not only for humans but also for a variety of insect pests. Sanitation and insect control practices are the first line of defence for reputable manufacturers against a variety of potential pests including those which arrive with incoming raw materials. Various beetles, moths and their larvae can feed on cocoa beans including the cigarette beetle and rust-red beetle although a variety of control measures including insecticides are avaliable depending on regulatory legislation in the countries of manufacture and sale. The Ephestia moth or cocoa moth is particularly troublesome because it lays its eggs away from its food and can feed on chocolate products as well as cocoa beans. Therefore, even though the processing times and temperatures of chocolate manufacture are high enough to ensure that few if any larvae survive, there is still potential for infestation during storage of the finished products. Manufacturers may take every precaution to prevent infestation in thir plants and warehouses but they must also encourage wholesalers and retailers to maintain a sanitary storage environment at temperatures and humidities which do not encourage insects to thrive. This is particularly important since the products are likely to be in these latter phases of distribution longer than they are in the manufacturer’s possession, yet it is the manufacturer’s brend name which is on the package.

Humidity:

Some of the effects on chocolate of storage at higher humidities have been mentioned in the discussions of water activity and investation. Another defectwhich occurs frequently at storage conditions of 80% RH and above is sugar bloom, a cloudy grey or white appeareance produced by the development of fine sugar crystals on the chocolate surface. This occurs at high humidities because condensation readily forms on the surface, the deposited moisture leaches some of the sugar from the chocolate and this sugar later crystallizes. The occurrence of sugar bloom can be affected by the type of carbohydrate sweetener used if sweeteners other than sucrose are allowed in a given country’s standarts for chocolate or if the product is a non-standart “chocolate”. use of unrefined sugar with high moisture content and hygroscopic activity can also induce sugar bloom. Finally, rapid transition from frozen or cold storage to warmer temperatures of even modest humidities can induce condensation and sugar bloom, as well as possible damage to wrappers or cases which become damp. Although relatively harmless in effect on flavor and texture, appearance of sugar blomm is of concern because consumers can mistake it for mold growth.

Oxygen:

When exposed to the action of air, fats and oils containing unsaturated fatty acids pick up oxygen and form aldehydes and ketones which give characteristic “off-flavours” described as tallowy, fishy,metallic cardboard or painty. The collective term “rancitidy” is often applied to all of these flavors but this one term does not reflect the variety and complexity of the underlying oxidation reactions and their products. Indeed, similar aldehydes and ketones are part of the natural flavors of other foods; they simply stand out as “off”at certain levels in chocolate. fortunately, cocoa contains tocopherols, fat soluble vitamin E comrounds which are rtained in cocoa butter and finished chocolate and which have antioxidant properties. In fact, while avariety of antioxidants are avaliable as additives, Lees and Jackson conclude that “There is little value in adding antioxidants to pruducts containing hardened vegetable oils or cocoa butter alone”, because of the inherent stability of these fats. However, this form of deterioration can occur under very adverse conditions since the reactions are catalyzed by moisture, heat, light and certain trace matels. Therefore, just as for the storage defects discussed earlier, appropriate packaging and storage conditions are important in discouraging oxidative rancidity. Milk chocolates may be slightly more susceptible; “white chocolates” will be much more so with their lower level of antioxidants due to the absence of cocoa solids, although some will still be avaliable from cocoa butter. Insuring proper storage (temprature, humidity, etc.) and quality of raw materials (e.g. low levels of certain metals) can greatly inhibit the oxidative reactions.

Heat:

As already discussed, heat abuse exacerbates virtually every form of storage defect. However, there is no more dramatic effect on the shelf life of chocolate then the direct effect of heat itself. The melting characteristics of chocolate at or near human body temperature give chocolate its uniquely pleasing mouthfeel and flavor relese proporties. But it is precisely this melting behavior which makes chocolate so vulnerable to relatively short storage periods at or above body temprature. After only minutes at these tempraturs, chocolate will melt, at least partially, and it is unlikely to resolidify in an acceptable form. Aside from obvious distortions in the product’s shape, the textural proporties and appearance of chocolate are highly dependent on the conditions under which it is cooled and solidified. Manufactorurers strive for optimum conditions during initial production but consumers will not reproduce these conditions when resolidifying a chocolate bar which was left in the sun. Milder temprature changes can be as harmful as more severe ones if they are repeated. In fact, temprature cycling is some times used as a means for accelerating storage studies in a laboratory seting. This leads us to the realited topics of cocoa butter cryztallization, chocolate tempering and the storage defect known as fat bloom.

SHELF LIFE OF CHOCOLATE CONFECTIONNARY: THE INFLUENCE OF OTHER INGREDIENTS:

A great deal of chocolate is not consumed as pure, solid chocolate but as part of confectionnary items which include nutmeats, nut butters, fruits, caramels, coconut, fondants, creams, jellies, wafers, biscuits or any number of other ingredients alone or in combination. These other ingredients have stability issues of their own which will influence shelf life of convectionery item. Most of these issues are beyond the scope of this chapter, but interactions
between chocolate and these other ingredients can influence the stability and likelihood of storage defects in the chocolate itself.

We have already seen that the addition of milk or milk fat can influencethe likelihood of some storage defects relative to plain or dark chocolate. another defect which becomes more likely with the simple addition of milk is hydrolytic or lipolytic rancidity. Hydrolysis occurs when fats are broken down into their constituent fatty acids, some of which contribute a soapy taste, hencethe term “soapy rancidity”. Most often hydrolysis is brought about by enzymes such as lipases. These fat-splitting enzymes are present in milk products as well as egg albumen, coconut and lauric fats, all of which can be in confectionary “centers”.

Confectionary items containing nut and nut butters are much susceptible to oxidative rancidity, fat bloom and infestation. Most of the oxidative rancidity problems are due to the inherent instability of the nut oils in the presence of the oxygen or trace metals present in the confection or from the environment. In this interaction between chocolate and nuts, the chocolate itself wiil be more susceptible but the nut itself may benefit from the effect of chocolate’s natural antioxidants. The net effect of this exchange will determine shelf life in general, chocolates with nut ingredients have shorter shelf life then solid chocolates.

Nut oils are also responsible for greater susceptibility to fat bloom. Oils from the nuts or butters can migrate into the chocolate causing softening and wet spots on the chocolate. This migration facilitates the movement of all fats to the surface which will appear as fat bloom when recrystalization takes place. This will also be concern for pruducts with any kind of high fat center.

Nuts themselves areprone to infestationas the pestsbore into shells and nutmeats. Roasting can alleviate this consern but the presence of nut containing chocolate products inplants and warehauses increases the need for vigilance in pest control.

With regard to lower fat confectionery components, many storage concerns will pertain the moisture. In some products, complete chocolate coverage of a soft center (e.g. fondant cream) is nessesary to keep the center soft and moist: cracks and pinholes can result in premature drying out. In products with multiple components, movement of water between components,such as from caramel to biscuit, can result in a soggy biscuit with limits shelf life. Under adverse storage conditions or over longer storage periods, chocolate may absorbe moisture from other confectionery components and this can exacerbate the texture problems described earlier regarding moisture pick-up from the atmosphere. Formulating to make water activities of different components more similar or using protective coatings may alleviate some of these water migration problems and help to extend shelf life.

IDEAL STORAGE AND THE DEFINITON OF SHELF LIFE:

Ideal storage conditions for chocolate confectionery products will vary somewhat depending on ingredients but some authors suggest finished stock storageas cool as 10o C at 50% RH. Temperatures lower than this, including frozen storage, may be desirable for shipping or storage in tropical climates or for other business reasons but this should be considered carefully because of cost and the risks which are entailed. Some componenets of confectionery items do not freeze thaw as well as the chocolate itself. Any storage under 10oC increases the risk of condensation, raising the possibility of sugar bloom and damage to packaging as the products are returned to normal atmospheres. The transition requires an intermadiate room of relatively dry air. Tempratuers as high as 65oF are probably still within the optimum range for most products while minimizing costs and some of the risks of cooler storage. In case, stability of storage conditions are critical.

Ultimately, defining shelf life of a chocolate confectionery product is a relatively arbitrary desicion on the part of the manufacturer. Since microbiological risk is fairly constant with age it is not a finishing factor. In making this desicion, the manufacturermust first be aware of the importance of various product characteristics in influencing consumers’ judgements of quality in a given market place. In some markets, any appearance of fat bloom may cause strong negative consumer responce while certain off-flavors may be more important in other markets. Once the important diamentions of qulity are known, the next step is to measure changes in these diamentions as the products ages. Although mechanical instruments can help, the ultimate instrument for the most dimensions of any food food product is the human sensory system. Systematic, unbiased sensory evaluation can be conducted using either consumers or trained tasters. Modifications of the sensory method described earlier can be made such that Vn in that diagram represents a different temprature/humidity or some other critical aspect of storage. The shelf life of the product should be based on the product’s sensory performance, over time, under not only the most likely storage conditions but under more stressful conditions which the product might experience during distribution and storage.once the important dimensions are known and measured, the final, most arbitrary decision is to establish the limit or cut-off criterion. Athe product ages, how low must a consumer “liking” score go before the shelf life cut-off is reached? How high must a trained taste panel’s raitings of an off-flavor get? Statistical definitions such as “a decline of X standard deviations” are common because they help make this desicion consistent. However, deciding what X should be is still relatively arbitrary.

As some of the most desirable, appetitive foods in the markets in which they are consumed, consumers have high expectations for chocolate confectionary items on virtually all quality dimensions. When making decisions about the shelf life of chocolate items, statistical or otherwise, it is as important to understand consumers’ dimensions of quality and their expectations as it is to understand the chemical events which determine change or stability in the products.