PROCESSING AND PRODUCT QUALITY
The components of food product quality include:
A seventh component of quality in the minds of many consumers is that of convenience
These components are dependent upon the composition of the food, processing methods, packaging and storage. In many cases the shelf life and convenience built into the product by the manufacturer dictates the safety, healthfulness, flavor, texture and color attributes of the product.
In many cases compromises are made to achieve desired shelf life or convenience. This is illustrated for milk in the following table, where product attributes are changed to achieve increased shelf life.
| PRODUCT | SHELF LIFE | PROCESS | COMMENTS |
| Fluid milk | 2 weeks under refrigeration | HTST pasteurization | Retains most of the characteristics of unprocessed milk |
| UHT fluid milk | 3-6 months at room temperature | UHT pasteurization and aseptic filling in plastic packages | Higher heat produces changes in flavor; off flavors generally develop after 90 days due to chemical changes |
| Evaporated milk | 1-2 years at room temperature | Concentration and retort sterilization, canned | Higher heat that UHT pasteurization causes brown color and caramelized flavor; often thickens on aging |
| Spray dried whole milk | 1-3 years at room temperature | HTST pasteurization, concentration and spray drying | Must be reconstituted for use; process changes flavor; shelf life depends on degree of oxidation during storage - which depends on Aw, packaging materials and temperature of storage |
The extension of storage life of products generally involves heat treatments, refrigeration or freezing or reduction of water activity by either addition of water binding agents (sugars, etc) or drying. Such processes, while improving shelf life almost always have some effect on the components of the food:
The factors which influence changes for various ingredients in foods include the following:
Proteins:
| heat denaturation which changes solubility and texture of foods |
| light oxidation causes off flavors |
| enzymatic degradation can cause changes in body and texture and also bitter flavors |
| freezing can alter protein conformation and solubility in some cases |
Lipids:
| enzymatic hydrolysis can cause off flavors - such as soapy or goaty, depending on type of oil; |
| also makes frying oils unsuitable for use; can change functionality and crystallization properties |
| oxidation of unsaturated fatty acids causes off flavors |
Carbohydrates:
| high heat treatments cause interactions between reducing sugars and amino groups to give Maillard browning and changes in flavor |
| hydrolysis of starch and gums can change texture of food systems; some starches can be degraded by enzymes or under acidic conditions |
Vitamins:
-depending upon the vitamin, losses can occur when the food is heated, exposed to light or to oxygen
A summary of effects of some processing on food products is shown in the following table:
| Process | Effects |
| High Heat treatment | Inactivation of enzymes, destruction of microorganisms; browning; flavor changes; texture changes |
| Freezing | Minimize of microbial growth;
slowing the rate of chemical reactions; disruption of cellular material (softening); precipitation of proteins on thawing |
| Packaging | Improper packaging or packaging materials can permit the transfer of oxygen into the product and cause off flavors; moisture transfer into packaged foods can cause caking, increase in the rate of chemical reactions and permit enzymes to action of food constituents |
| High shear pumping | Can cause size reductions; production of foams (either desired on undesired); disruption of protein structure; activation of enzymes in some cases. |