Quality Factors for Ice Cream
Many factors, including the flavor, body and texture, melting quality, color, package, appearance, and influence quality, the overall acceptability of the product by consumers.
Appearance is the first aspect of a product to influence customers. This may be the appearance of the package in the supermarket cabinet, or it may be the appearance of the ice cream in the serving dish on the table. Appearance of the package is important, because obviously if the package is not attractive to prospective customers, they will not buy it. The quality of the ice cream itself will never be evaluated if the package doesn't attract interest.
Appearance also includes the ice cream's color. It has a marked psychological effect on acceptability of foods of all types, and ice cream is no exception. How often have you seen a dish of chocolate ice cream with a dull, murky appearance reminiscent of mud, or a strawberry ice cream so brightly colored that you know it has to be imitation? The various quality factors concerning appearance influence our opinion as consumers even before we taste it, a product, and therefore these factors should be carefully considered and adequately addressed in a quality-control program. A good start has been made in producing a readily acceptable product when it has been made to look delicious. Once the appetite is whetted and a delightful flavor is anticipated, consumers are psychologically ready for a delicious taste sensation. At this point, all other quality factors become subordinate to flavor. If the flavor is not up to expectations, consumers will be disappointed and will consider the product to be of poor quality, regardless of the merits of other quality factors.
Appearance of the ice cream itself is normally where most consumers start to differentiate among the qualities of ice creams. Here, dipping characteristics--gummy, sticky body; coarse, icy texture; pleasing color indicative of flavor; and appearance of flavoring pieces (if present)--all play a part in influencing consumers.
How the ice cream melts down (melt-down) is a minor factor affecting appearance, and is normally noticed only in extreme cases--either adversely as a curdled, wheyed-off melted product, or favorably as an especially smooth, creamy, rich-appearing melted product.
Textural characteristics of the ice cream are important and influence by may factors. If two samples of the same ice cream are handled differently to produce a coarser (icy) texture than another with the same formulations, the sample with the better texture will be considered to a better flavor. In eating ice cream, one becomes intimately interwoven with flavor sensations, and the ice cream texture, in this case icy or course can either complement or detract from the apparent flavor.
Milkfat accounts for most of the rich-sensations of ice cream, and only a limited amount of substitution with other ingredients can be made without changing the product's characteristics. Milkfat contributes a mellowness and flavor as no other constituent can. Emulsifiers are helpful here, as are the phospholipids found in good-quality buttermilk powder, but much reduction in milkfat will affect the eating quality of the product.
Milk solids-not-fat (SNF) contributes to flavor but are most important to the body and texture of ice cream. Proteins bind water to act as stabilizers, have an emulsifying effect on the fat, and give viscosity and chewiness to the body. Milk solids also include salts and lactose. If used in excessive amounts, milk solids cause a condensed-milk or milk protein flavor, but in most cases saltiness will be the limiting factor on the amount of milk solids that can be used.
For many years the fear of lactose crystallization (described as sandy) forced manufacturers to limit the solids-not-fat in ice cream to 12% or less. Today, however, there is little danger in sandiness developing under commercial conditions. In fact, there is no excuse for sandiness in ice cream because technical advances have made it possible to eliminate this defect. Some experimental data indicate that the incidence of sandiness is increased when the drawing temperature is decreased.
Because milk solids tend to mask delicate flavors, it is necessary to use more flavoring materials in order to make the flavor apparent. This is especially true for vanilla and fruit flavors, in which high levels of solids-not-fat interfere with the flavor. The more SNF, the more flavoring will generally be needed. Sweeteners play an important role in any ice cream, and the current trend is to add them in increasing quantities. They have three important functions: to give sweetness, to add to the solids content, and to lower the freezing point so that the product is soft and smooth at low temperatures, say 10 F.
For many years the industry has taken it for granted that the desirable level for sweetness is 15%, based on consumer tests. Increased sweetness in fruit ice creams is particularly important. Because fruit acids depress the apparent sweetness and because the added bulk of the fruit dilutes the mix, the body and texture is poorer. The higher sugar level brings out the fruit flavor and at the same time improves the body and texture. Recent trends in the use of sweeteners have been to increase the amount of corn syrup or corn solids and to use blends. Changes that result in a less expensive product are readily accepted.
The use of additional corn solids is justified, but not merely on the basis of economics. Corn syrups got their start initially as table sugar substitutes during World War II, when they were used to stretch the sugar rations available to ice cream manufacturers. During this period it became apparent that corn syrup had certain desirable properties that imparted improved quality to the ice cream, if the corn syrup was used wisely. Corn syrup improves and helps to maintain smoothness when the ice cream encounters temperature fluctuations of heat-shock. It gives a desirable chewiness to the body of the product due to the presence of dextrins, high-molecular-weight polysaccharides that remain after acid hydrolysis of the cornstarch to produce corn syrup. Not all corn syrups have the same composition; in fact, there is a considerable range depending primarily on the extent of hydrolysis used in their preparation. Corn syrups have a characteristic flavor of their own, and if used in excessive amounts they interfere with natural flavoring materials. Even when used in sub-threshold levels, when the flavor of the syrup itself cannot be detected, there is a masking effect on ice cream flavor, particularly for vanilla.
Gums of various kinds are useful as stabilizers in ice cream because of their characteristic property of imbibing or absorbing large amounts of water. This characteristic is effective in limiting the natural tendency of ice cream to become coarse in texture during storage. Numerous types of animal and vegetable products have been found effective in ice cream and as a result a considerable range of stabilizers is available on the market. The primary purpose of stabilizers is to maintain the smooth texture by inhibiting the formation and growth of ice crystals, but other considerations are also important. Their effect on flavor, color, viscosity, whipping ability and meltdown should also be considered.
The effect of the stabilizer on viscosity in relation to temperature and age has very practical significance. If the viscosity is increased immediately and greatly, the mix will be difficult to cool. On the other hand, if the stabilizer imbibes water slowly and takes time to establish a gel structure, an aging period is necessary, and viscosity will vary with age. Constant physical characteristics are important when mix is sold, or when it is necessary to freeze the mix immediately after processing.
Some gums are especially effective in increasing viscosity; others produce a heavier body or provide better resistance to heat shock. Many have certain limitations if used alone, such as a curdy meltdown or coagulation of the milk proteins, and cause the mix to whey-off. Most commercial stabilizers are blends or various gums standardized to give uniform results from lot to lot. These products are more effective in maintaining good texture and aid in producing a heavier, chewier ice cream.
Emulsifiers have become more uniform, more versatile, and almost essential to modern ice cream manufacturing. They are especially useful in producing a stiff, dry product for specialty items, but they also have their place in regular manufacturing and packaging operations. The ice cream is smoother, creamier, and more melt-resistant when emulsifiers are used. However, excessive use causes an unnatural slickness, a partially churned appearance, and product that does not melt. In some cases the flavor is adversely affected, too.
It is apparent from this discussion that each ice cream ingredient has specific functions that it alone can perform most effectively. However, there is a definite overlapping of some of the functions. For example, all ingredients influence body and texture, so that a variety of variations can still produce an acceptable product. One must be careful when altering ingredients to assure that the eating quality is not impaired.
Composition control is essential in obtaining and maintaining quality. The ice cream's ingredients serve specific functions in supplying the characteristic properties of the final product. Several ingredients may influence some properties, so that similar results can be obtained by altering the quantities of any or all of them. Other properties of ice cream depend primarily on one ingredient.