3.28.2012

FACTORS AFFECTING FOOD QUALITY


INTRODUCTION

The quality of a food is defined from two perspectives: scientific status and consumer preferences. Scientific factors affecting the quality of a food include composition, spoilage, colorants, additives, nutrients, flavorants, functional ingredients (affecting health), contamination, general safety, etc. Consumer preferences are linked directly to the human senses such as sight, touch, smell, taste, and mouthfeel. Visual factors include color, moisture, overall appearance, etc. Tactile factors include sliminess, elasticity, softness, hardness, etc. Factors responsible for taste and smell cover many specific chemicals. Mouthfeel refers to texture, softness, tenderness, chewy sensation, and so on. In the last 10 years or so, food quality has been defined by most professionals to include “health” and “safety.” The nutrition and safety of foods have always been important, especially so since the 1970s.

The word “health” now includes manipulating certain chemical components in food to increase the positive impact of food on our health. “Safety” now refers to a whole spectrum of new legal or recommended requirements for both fresh and processed foods. These requirements are designed to exclude or prevent undesirable agents (biological, chemical, physical, environmental, and extraneous) in our foods. For ease of reference, we can consider that the quality of muscle foods (meat, poultry, and seafood) is the composite picture of many factors, and this chapter provides a brief mention of some of them.

BIOLOGY AND GENETICS

Obviously, the quality of any muscle food depends first and foremost on the genetics and biology of the animal. The beef from a young animal is more tender than that from an old animal. Due primarily to biological reasons, muscle from some parts of beef cattle is tastier and more tender than those from another part. Chickens are more tender than turkey. White meat is biologically different from dark meat. Of course, the preference of a consumer varies with regard to the two different kinds of meat. Saltwater fish is different from freshwater fish. Some fish have more bones than others. Western consumers prefer fish with fewer bones while most often the opposite is true for Asians.

NUTRITION

Recently, the nutrition of food has reached an alltime high as far as its impact on our health is concerned. There is no doubt the majority of Americans consider a quality food as one with high nutritional value. Some salient points follow:

1. Meat and poultry are nutritious because of their high source of protein, vitamins, and minerals.
2. The high content of fat and cholesterol in land muscle foods is undesirable. Thus, “lean” is in.
3. Fish and shellfish are an important part of a healthy diet. Fish and shellfish contain highquality protein and other essential nutrients, are low in saturated fat, and contain omega-3 fatty acids.
A well-balanced diet that includes a variety of fish and shellfish can contribute to heart health and children’s proper growth and development.

FLAVORS AND AROMA

One major reason, among many, that we like to eat is because food tastes good, which equates to flavor and aroma. Extensive research over the past 25 to 30 years has identified more than 1,000 flavor compounds in meats. However, a single compound or group of compounds responsible for “meaty flavor” has not and perhaps never will be identified due to the overall complexity of meat flavor. Meat flavor is dependent on the pool of flavor precursors in the meat tissue and the chemical reactions that occur during processing. Processing and subsequent storage contribute to the development of the characteristic flavors of meats.

Because the precise flavor precursors vary between and within species, beef, pork, lamb, and poultry each have distinctive flavor characteristics. The quality of meat and poultry is to a large extent defined by its flavor and aroma. In general, fresh saltwater fish are almost odorless because they contain a small quantity of volatiles while freshwater fish give off pyrrolidine and other earthy-odor compounds.

The compounds responsible for the development of flavor during seafood cooking can be classified in two groups. One, which represents the pleasant cucumbed green, almondnutty, and potato aroma notes, consists of highly volatile, low molecular weight compounds belonging to various chemical classes such as aldehydes, ketones, alcohols, esters, nitrogen,phenols, and sulfur-containing compounds. The second is due to water soluble, low molecular weight free amino acids (taurine, glutamic acid, glycine), nucleotides (purine derivatives), organic acids (lactic acid), and inorganic salts (Na, K, Cl).

Biogenic amines are nitrogen-containing compounds, which are present at very low levels in fresh fish. However, during storage and deterioration, biogenic amines can be produced by amino acid decarboxylation from bacterial enzymes. Among biogenic amines formed, putrescine and cadaverine have a putrid flavor while histamine and phenylethylamine have a pungent and fishy flavor, respectively. Biogenic amines are thermally stable and, therefore, have been used as indices to determine fish freshness. Volatile amines such as trimethylamine (TMA) or dimethylamine (DMA) are formed from trimethylamine oxide (TMAO), and these compounds also serve as a quality index for marine fish.

COLOR

The first impression that a consumer receives concerning a food product is established visually, and among the properties observed are color, form, and surface characteristics. Color is the main aspect that defines a food’s quality, and a product may be rejected simply because of its color, even before other properties, such as aroma, texture, and taste, can be evaluated. This is why the appearance (optical properties, physical form, and presentation) of meat and poultry products at the point of sale is of such importance for the industry. Regarding the specific characteristics that contribute to the physical appearance of meat and poultry, color is the quality that most influences consumer choice.
Food technologists have a special interest in the color of food for several reasons. First, because of the need to maintain a uniform color throughout processing; second, to prevent any external or internal agent from acting on the product during processing, storage, and display; third, to improve or optimize a product’s color and appearance; and, last, to attempt to bring the product’s color into line with what the consumer expects. Put simply, the color of meat is determined by the pigments present.

These can be classified into the following four types:

1. Biological (carotenes and haemopigments), which are accumulated or synthesized in the organism ante-mortem.
2. Pigments produced as a result of damage during manipulation or inadequate processing conditions
3. Pigments produced postmortem (through enzymatic or nonenzymatic reactions)

Those resulting from the addition of natural or artificial colorants As a quality parameter, color has been widely studied in fresh-meat and cooked products. Dry-cured meat products have received less attention because in this type of product, color formation takes place during the different processing stages. Recently, new haempigment has been identified in this type of product. From a practical point of view, color plays a fundamental role in the animal production sector, especially in meat production (primarily beef and poultry,) since in many countries of the European Union, paleness receives a wholesale premium.


MICROBIOLOGY AND SAFETY

All foods contain microorganisms, some beneficial to and some with potential harm for mankind. With muscle foods, the beneficial ones are responsible for fermented meat and fish. Those potential pathogens are of concern. In the last 25 years, government records show that pathogenic organisms in meat, poultry, and seafood have been responsible for many deaths and injuries. Also, marine toxins pose big threats to our well-being considering that most of us enjoy eating fish and shellfish. It is not surprising that a quality muscle food must also be a safe one. In view of potential hazards from the consumption of muscle foods, state and federal agencies have developed and implemented stringent safety requirements in the processing of meat, poultry, and seafood.

PROCESSING

The quality of any muscle food is obviously affected by the way it is processed. Why do we want to process food? At present, there are many modern reasons why foods are processed, e.g., adding value to a food, improving the visual appeal, convenience. However, traditionally, the single most important reason that we wish to pre-process food is to make them last longer without spoiling. Probably the oldest methods of achieving this goal are the salting of meat and fish, fermenting of milk, and pickling of vegetables.

Foods are made from natural materials, and like any living matter, will deteriorate in time. The deterioration of food, or food spoilage, is the natural way of recycling, restoring carbon, phosphorus, and nitrogenous matters to the good earth. However, putrefaction (spoilage) will modify the quality of foods resulting in poor appearance (discoloration), offensive smell, and inferior taste. Food spoilage can be caused by a number of factors, chiefly by biological factors, but also by chemical and physical factors. Consumption of spoiled foods can cause sickness and even death. There is no doubt none of us consider spoiled foods as having quality.

Selected examples will illustrate how food processing can affect the quality of a food product: Heat application. All of us know that overheating tender meat and chicken usually means toughness. The same is especially true for seafood. Heat removal or cold preservation. Freezing is a good example. Most of us are familiar with freezer-burn of meat, chicken, fish, shellfish, or other products left in the freezer over extended periods of time.

Evaporation and dehydration. Food drying has been popular since the beginning of time. Destruction of nutrients, especially vitamins, is one drawback to this method of preservation. Fermentation. In general, of meat, poultry, and fish products, fermented meat such as sausages is most popular. The quality of a sausage is to a large extent determined by the consumer, e.g., dry, sweet, salty, and pickled. Each method affects the quality in terms of nutrients, hardness, tenderness, and flavor.
New technology. There are numerous new technologies in food processing such as irradiation, microwaving, and ohmic heating. Each method affects the quality of a food in various ways. The finished product requires packaging. The obvious reason for packaging a food product, muscle foods or other, is to protect the food so it will not be exposed to the elements until it is ready to be prepared and consumed. The quality and shelf life of a food, especially a muscle food, depends very much on the way it is packaged.

SENSORY ATTRIBUTES AND THE CONSUMER

The sensory attributes of muscle foods are related to the senses of taste, smell, sight, feel, and sound. Of all the foods consumed, muscle foods have the lowest tolerance for complete sensorial acceptability. A muscle food is either acceptable or unacceptable with little in between. Predominately, the consumer visually assesses the color and surface texture of the muscle. The preparation technique of consumer choice is utilized, thereby altering the sensory attributes (usually completely).

The consumer cooks or prepares the muscle food as they prefer, changing the surface color, appearance, and texture. The internal altering of texture and flavor is a result of the preparation or cooking process as well. This will vary depending on the many methods applied. For instance, the muscle may be grilled, baked, broiled, or otherwise prepared, all with different fluctuating end results. Consumption of muscle foods is one of the most pleasurable eating experiences. The satiety value applied by the consumption of a muscle food is great when comparing the satisfying effect of foods in general. This is why the sensorial properties of muscle foods can be viewed as often more important than that of other foods.

GOVERNMENT STANDARDS AND SPECIFICATIONS

The technical information in this book is applicable to food scientists and technologists worldwide. However, users from the United States will be very interested in the current government standards and specifications for muscle foods (meat, poultry, and seafood) since such documents usually include quality factors. Since many countries use the United States as an example in formulating their standards and specifications for muscle foods, scientists, technologists, and engineers from the international community may also benefit from information included in the appendix.

SUMMARY

This chapter provides a short introduction to the factors affecting the quality of foods, especially muscle foods. More details on most of the factors will be provided throughout the book.

By Y. H. Hui in the book 'Handbook of Meat, Poultry and Seafood Quality' Edited by Leo M. L. Nollet, Blackwell Publishing UK  2007, p. 3-6. Digitized, adapted and illustrated to be posted by Leopoldo Costa.

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