Improving the Safety and Quality of Milk

Improving Quality in Milk Products

Mansel W Griffiths, Mansel W Griffiths

• Publisher: Woodhead Publishing
• Year: 2010
• ISBN:
  9781845699437
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

Consumers demand quality milk with a reasonable shelf-life, a requirement that can be met more successfully by the milk industry through use of improved processes and technologies. Guaranteeing the production of safe milk also remains of paramount importance. Improving the safety and quality of milk provides a comprehensive and timely reference to best practice and research advances in these areas. Volume 1 focuses on milk production and processing. Volume 2 covers the sensory and nutritional quality of cow's milk and addresses quality improvement of a range of other milk-based products.The health aspects of milk, its role in the diet and milk-based functional foods are the focus of the opening section of Volume 2. Part two reviews essential aspects of milk quality, including milk microbial spoilage and chemical deterioration, sensory evaluation, factors affecting milk vitamin and mineral content and the impact of packaging on quality. Chapters in part three look at improving particular products, such as organic milk, goat milk and sheep milk. The impact of milk on the quality of yoghurt and cheese is also covered.With its distinguished editor and international team of contributors, volume 2 of Improving the safety and quality of milk is an essential reference for researchers and those in industry responsible for milk safety and quality.

• Examines the sensory and nutritional quality of cow's milk and addresses quality improvement of a range of other milk-based products
• Reviews the health aspects of milk and its role in the diet, as well as the essential aspects of milk quality, including microbial spoilage and chemical deterioration, sensory evaluation and factors affecting milk vitamin and mineral content
• Discusses various application requirements of milk such as milk quality requirements in yoghurt-making, cheesemaking, infant formulas and applications of milk components in products other than foods

Part I

Nutritional aspects of milk

1

The role of milk in the diet

H. Bishop MacDonald, Nutrisphere, Canada

Abstract:

The Bible speaks of milk and honey and, interestingly enough, these two are the only foods whose sole purpose is as food. Milk, unfortunately, has become the victim of much mythology that has served to obscure its extremely important role in supplying nutrition to most of the world’s inhabitants. This chapter will look at the variety of mammals from which milk is derived worldwide, the variety of forms in which it is consumed and, most important, the nutritional contribution that milk makes to the overall well-being of humans. Macronutrients and micronutrients will be discussed along with milk’s impact in various stages of life as well as the likely nutritional status of those who abstain from consuming milk in any form.

Key words

milk

dairy

nutrition

nutrient deficiencies

1.1 Introduction

Although it has not been possible to pinpoint the exact date at which milk from various species was used to nourish humans, it is a pretty safe bet that as soon as animals were domesticated (about 9000 BC), their milk, in a variety of forms, was used as food for humans (McGee, 1984). Not only were the animals of longer use for food when kept alive instead of being slaughtered for their meat, ruminants (the primary source) thrived on dry grass thereby converting an otherwise useless commodity into a nutritious product. Today we are most accustomed to thinking of cows as the major supplier of milk (with goats becoming increasingly popular as sources of milk and cheese), but they were neither the first nor the only source. Along with milk from goats and sheep, humans have used at various times in history the milk from camels, yaks, water buffalo, reindeer, donkeys, horses and zebra, to name but a few of the mammals that have been called into service. Fluid milk is consumed both as a food and as a thirst-quenching beverage both in its fresh form and as a fermented and/or cultured product. Its transformation into cheese and yoghurt is arguably the first instance of a ‘convenience’ food, certainly for the camel-drivers that took advantage of this spirit of cooperation between food and bacteria. For millennia now mammalian milks and milk products have been a staple in the diet of most cultures. To say that milk is nature’s most nearly perfect food is not stretching the truth, as can readily be seen by examining the myriad of nutrients that constitute this amazing foodstuff.

This chapter will examine milk consumption worldwide, including source animals, the variety of forms in which milk is consumed, and the various ethnic traditions that dictate its use and the cultural impact of milk as a food. The important role of milk in the diet will be addressed with particular attention to the nutritional impact of milk on the well-being of humans. The part played by milk at various stages in the life cycle will be discussed as will the likely nutritional status of those who, either by intent or circumstance, abstain from consuming milk in any form. Finally, there will be a list of reliable sources of information that readers can access to further their knowledge of milk and milk products and a summation of the author’s advice regarding recommended consumption of these foods.

1.2 Milk consumption worldwide

Tempting though it is to generalize about worldwide milk consumption (highest in Scandinavia, lowest in China, that kind of thing), in fact milk consumption in any country is dependent on many factors. Some of those factors are things like age, sex, ethnicity, and a combination of all three. The United States and Canada, for example, are considered dairying countries with a relatively high level of milk consumption. But who is drinking the milk, and what kind of milk are they drinking? Many factors contribute to milk consumption (Brewer et al., 1999) including beliefs, attitudes and sensory evaluation. These same authors found that milk drinking among women was actually quite low, with 23 of the 100 subjects admitting that their milk consumption was close to non-existent. Researchers in New Zealand (Gulliver and Horwath, 2001) found a similar situation in their country and attributed the situation to factors including the belief that milk is fattening and perceived lactose intolerance. Male adolescents, on the other hand, have been shown (Larson et al., 2003) to have a higher intake of dairy products and calcium than their female counterparts.

1.2.1 Variety of forms and sources of milk and milk products in disparate cultures

Fond though the young western male might be of a cool glass of milk, he might decline the offer if the source of that milk is other than a cow. While goat’s milk and sheep’s milk are becoming more popular in northern Europe and North America, in many other parts of the world those milks have long been traditional beverages. What further distinguishes one culture from another is not just the source of their milk, but the form in which it is consumed. Probably first used in the Middle East, Turkey and Iran, one can easily imagine yoghurt developing spontaneously as milk was transported in goat skin bags as nomads crossed the desert. The combination of naturally occurring bacteria, sun and constant churning from the camels’ marching were a sure-fire bet to produce the first fermented milk product. On the other hand, if the saddlebags were made from a young goat’s stomach, then the rennin it contained would see the resulting product become what we know today as cheese. Other forms that serve as the delivery system for milk’s goodness include fermented milks like kefir, buttermilk, cottage cheese and whey.

In a nutshell, then, various cultures have traditionally used various forms of milk, and that use depended a good deal on the age and stage of life, ranging from the feeding of fluid milk to children, to widespread use of cheese and yoghurt, to the burgeoning idea that yoghurt itself, by virtue of various bacteria, confers health-promoting advantages.

1.3 Nutritional benefits of milk

If we were in the middle of the twentieth century a discussion of the benefits of milk would hardly be deemed necessary: practically everyone accepted that milk had a place in a healthy diet – although excessive intake of any particular food was discouraged. But then food consumption began to lean toward ‘political correctness’ and milk avoidance became, in some circles, to be seen not only as healthy (all that cholesterol and saturated fats!) but also as a solution to world hunger (because grazing cows were consuming food that would otherwise go to humans) and a safeguard for Mother Earth (WHO Technical Report Series 916, World Health Organization, 2003). Various groups aggressively attacked the use of animals and their by-products, and the WHO/FAO Report Diet, Nutrition and the Prevention of Chronic Diseases, in a memorable expression of a preference for illusion over evidence, laid the blame for the increasing incidence of non-communicable diseases in developing countries at the hooves of cows and their milk (WHO Technical Report Series 916). Before addressing, then, the myriad ways in which milk can contribute to the overall well-being of humans, let’s first look at the natural resources expended on the raising of mammals for their milk. Essentially, world hunger is a political and economic problem, not one of production. Beyond that, most agricultural land in the world, nearly 70%, produces grass. Grass isn’t a food for humans, but for ruminants that can convert grass and other forages into human food. Forages also play a soil conservation role on cultivated land. Furthermore, the grains that ruminants eat are different: livestock eat a lower grade that isn’t suitable for human consumption (Pimentel, 1980; Pimentel and Pimentel, 2003). This very brief discussion certainly doesn’t lay the issue to rest; I’ll leave that to others with more expertise on the subject elsewhere in this book.

1.3.1 Milk’s macronutrients: protein, fat and carbohydrate

Milk protein

Fluid milk contains 30–35 g/litre of total protein. This protein is of high nutritive quality with a biological protein value of 0.9 compared to the 1.0 of whole egg protein (a slight inferiority in sulphur amino acids denies milk protein first place). The major proteins of milk include caseins, lactoglobulins and lact-albumins, and are classified as either caseins (82%) or whey proteins (18%). Due to their structure caseins are readily digested and absorbed by the human gastrointestinal tract. The accumulation of ...