Abstract:

At the annual meeting of Chinese society of food science and technology held in Wuxi, the American dairy export association held a dairy forum, inviting

Experts from China and the United States discussed the raw material characteristics and innovation opportunities of milk protein. Four experts from the American dairy export association, Northeast Agricultural University, Zhongshan University and Fuzhou University discussed how to scientifically apply milk protein to develop new products in the food industry and meet the market demand from different perspectives.

Sarah Geddes, consultant, American Dairy Export Association

Using dairy ingredients to meet consumer demands

With the continuous prosperity of China's economy, Chinese consumers, especially urban residents, are facing more health challenges caused by lifestyle changes. The application of dairy raw materials can provide consumers with healthier food. Improving the protein content of daily diet can help healthy aging.

It is a global trend that consumers prefer more natural foods with clean labels. Dairy products are mostly foods with clean labels, so they are attractive. Dairy products can not only bring health, but also enhance the flavor of products, such as in beverages, snacks, dip sauce and food.

High quality protein should be evenly distributed in three meals a day throughout the adult life cycle. For a long time, nutritionists have considered the daily intake of protein or the reference recommended amount. However, the optimization of protein should not only consider quantity, but also consider quality and intake timing. Even distribution of intake in a day can effectively utilize protein. Research results show that breakfast protein content is usually the lowest, and milk protein can help fill the gap.

In 2020, the elderly aged 65 and above are expected to account for 11.8% of China's total population. By 2035, more than 70% of China's population will live in cities.

According to a health and nutrition survey conducted in China, only less than one fifth of the elderly over 60 years old in China have achieved the recommended protein to energy ratio. Whey protein or milk protein can be used in beverages, rice noodles, yogurt, frozen sweets, soups and many other foods to improve the protein content of these foods.

In 2015, the Canadian Society of dietetics and nutritionists and the American College of sports medicine jointly issued a position statement that young people should eat 20-25 grams of high-quality protein per meal, and middle-aged and elderly people should eat 30-40 grams of high-quality protein per meal. It can optimize the synthesis of muscle protein in the whole day by eating the appropriate amount of high-quality protein per meal. Through dietary supplement, it can promote the maintenance of muscle volume and muscle function, and help the overweight and obese people to achieve successful weight management.

Milk protein binding to plant protein can optimize protein quality. In 2013, the food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (who) proposed a new method to evaluate protein quality - digestible essential amino acid score (diaas). This new method is more accurate than PDCAAS, which has been used since 1998. According to the diaas method, milk protein can provide all the necessary amino acids, which can be used to bind plant protein and make more effective use of protein. Rice, wheat and corn are the main foods of Chinese diet, but they are not completely protein. Mix 50 grams of wheat and whey protein to form a complete protein. The complete protein can also be obtained by mixing corn and milk protein in the ratio of 40:60 G.

Whey protein and milk protein are concentrated in different degrees. In view of specific applications, many new materials with better application characteristics have also been developed, and their dispersity, thermal stability and gelation have been further improved. The thermal stability can be defined as the characteristics of no caking, precipitation, excessive viscosity and glue binding after UHT or autoclave high temperature treatment.

Milk raw materials not only provide nutrition, but also have various functions in processing. For example, the characteristics of frothing in ice cream and desserts, gel properties in cheese, yogurt, emulsification in soup and seasoning are all very good functions.

Application cases of innovative products

Whey protein beverage is a clear beverage made from whey protein isolate. The protein content of every 240 ml of beverage is 5g. Milk protein concentrate is a better choice if you want the beverage to have a milk tea like state. For the beverage as a whole, if the appearance is transparent, the pH value is generally 2.8-3.4. If the beverage is turbid, the recommended range of pH value is 3.5-4.5.

Whey protein fish minced sea product this formula can provide 8 grams of protein per 100 grams of food. The application of whey protein concentrate can improve the water holding capacity of fish cake gel and prevent the self dissolution of surimi.

The content of lysine in milk protein cereal flour is relatively low. Adding whey protein concentrate can strengthen the content of lysine. If it is used to make noodles, the strengthening of milk protein will also make the noodles stronger and more elastic.

The double protein beverage contains 30g protein, part of which comes from whey protein concentrate, part of which comes from soybean protein concentrate. The combination of milk protein and plant protein can ensure high protein quality and is more economical.

The protein in the breakfast bread formula comes from whey protein isolate and plant protein. Plant protein includes cereal protein in whole wheat, oats, flaxseed and millet. High protein plus whole grain is a popular new product trend in the world.

According to the survey data, there is a very high growth rate of whey protein products in the world. From 2005 to 2010, the annual compound growth rate of whey protein products in the world is 11%, and from 2011 to 2016, the growth rate is as high as 28%.

Professor Zhou Peng, director of International Joint Laboratory of milk protein functional ingredients, Jiangnan University

Design and development of milk protein ingredients based on nutrition and functional characteristics

How to adjust the relevant ingredients to better meet the needs of products in the four categories of commonly used milk protein?

First, milk protein used in high protein drinks.

Milk protein, also known as whole milk protein, contains almost all kinds of protein in milk. The solubility of whole milk protein concentrate is generally more than 80% - 90% when it is newly produced, but after a few months, even if it is stored in a cool place, its solubility will decline rapidly, which will greatly affect its application in beverages and reduce its solubility in beverages. The reason for the decrease of solubility is the aggregation of noncovalent bonds and the promotion of aggregation by calcium. If we want to improve its solubility, we can maintain its stability by adjusting calcium and the equilibrium state of micelles.

The strategy adopted, on the one hand, is decalcification. When the decalcification rate reaches 20%, the dissolution stability is greatly improved. The effect of decalcification by acid is more simple and efficient than that by ion exchange. Acid regulation consists of two steps. The first step is simple acidification. After acidification, part of the calcium in the whole micelle will be free from the original form of micelle calcium phosphate to the solution, and the liquid system of milk will be partially removed in the process of membrane filtration. In this way, the solubility and solubility stability of dry powder will be greatly increased. In the later stage, the pH value will be adjusted back, and the solubility will be improved better. The whole milk protein concentrate after acidification is transparent, which is a good choice for developing transparent protein beverage. At the same time, its foaming and emulsifying properties are also improved.

Second, whey protein used in infant formula milk powder.

Infant formula milk powder was mainly spray dried milk powder at first, but later found that the difference between human milk and cow's milk was very large. The whey protein content of human milk was obviously higher than that of milk. Therefore, infant formula milk powder is gradually changed to use whey protein ingredients. In recent years, the application of whey protein peptide has been increased. Whey protein peptide is added to infant formula milk powder mainly because many infants have allergic reaction to whey protein of cow's milk, and in consideration of digestion and absorption, whey protein peptide is used instead of whey protein. One problem is that if the degree of hydrolysis of peptide is not well controlled, it is easy to produce product caking.

In addition, compared with human milk, the content of α - casein in milk is very high, the content of α - casein in milk is low; the content of α - casein in human milk is low, and the content of β - casein is high. The improvement of technology can improve the yield of whey protein and obtain β - casein at the same time. Most of the first whey is extracted from the remaining whey which is used to make cheese. Now, the separation of whey and casein can be realized through membrane technology. Through membrane filtration and temperature reduction to 4 ℃, the product with the ratio of whey protein to β - casein close to 2:1 can be obtained. This ratio is very close to the composition of human milk, and the process is very simple. Casein, a by-product of casein, can be used to produce soft cheese.

Third, the milk protein in the protein bar food.

The protein bar made of WPI is very stretchable, and the protein bar made of casein is fine and even. If sodium caseinate is used, it has the same elasticity as rubber ball, but if soybean protein isolate (SPI) is used, the texture is rough and has a granular feeling. Different protein gives different texture and adapts to different needs. Sometimes we should emphasize its chewiness, sometimes we should emphasize its palatability, so we should choose different protein. Not only to control the type of protein, but also to control the nature of the powder in the process, including its size, composition changes.

Fourth, 3D printing of milk protein in food.

At first, researchers wanted to use milk protein concentrate (MPC), but later found that MPC alone was not good because it was too dry. MPC has a relatively strong water holding capacity, but it feels that its palatability is poor. When a little WPI is added into the MPC, the whole property changes greatly. The 3D printer has a good fluid property in the process of extrusion, but after extrusion, it also wants to have plasticity immediately. These two points are actually contradictory, which puts forward high requirements for materials.

With the appropriate ratio of MPC and WPI, 30% of the WPI here can be extruded well, hit layer by layer, and finally play a three-dimensional effect. With WPI alone, if it's less than 30%, it can't be typed out. When it's 30%, it can be typed out, but if it's slightly increased by 10%, it will flow soon. Therefore, in the whole process of using milk protein ingredients, not only to master the characteristics of simple ingredients, but also the mixing characteristics are very important. At present, it is seldom to use a single protein, but to integrate the characteristics of different proteins, to use mixed proteins, to integrate its nutritional characteristics and processing functions.

Liu Shutao, director of Institute of bioengineering, Fuzhou University

Lactose intolerance effect of different dairy products

In milk, lactose content is about 4.7%, in breast milk, lactose content is about 7.2%. Lactose has a variety of physiological activities, such as promoting the absorption of calcium, improving infant immunity and so on.

Lactose intolerance refers to that lactose can not be metabolized normally due to the lack of lactase when eating milk and dairy products, which leads to lactose entering the colon and the increase of osmotic pressure of the colon, leading to diarrhea. In addition, the intestinal flora in the colon will metabolize it, producing gas, causing abdominal distention and abdominal pain.

The lack of lactase, there are many situations, the adult is more the lack of primary lactase. Nearly 100% of the Chinese are lactose deficient. However, in life, the incidence of lactose intolerance does not seem to be so common, it is not said that more than 50% of people drink milk will have diarrhea. In dairy products, there are influencing factors of lactose intolerance. Through some changes of drinking methods, lactose intolerance may be improved to some extent.

Recent studies have found that the metabolism of some milk containing type A2 casein will produce a new type of peptide in the body, even if there is lactose in the milk, the symptoms of lactose intolerance will not occur. In order to verify, the researchers conducted a comparative test to see whether improving the processing of dairy products, changing the content of lactose in dairy products and using different β - casein dairy products can affect the occurrence of lactose intolerance.

First of all, the experiment designed the exclusion period, in which the volunteers with lactose intolerance first eliminated the milk in the body within a week, and then conducted the intervention experiment. The subjects were divided into three groups: the first group was fed milk with low lactose, the second group was fed fruit milk, the third group was fed fermented milk (yoghurt), and then they were given a one week clearance period.

Next, the milk comparison of type A2 casein was made. The first group was type A2 milk, the second group was mineral salt milk powder, and the third group was ordinary milk powder, which were all made in hot water to observe the consumption. After the recovery period, all people eat pure milk again, drinking at room temperature to observe the symptoms of lactose intolerance.

According to the experimental results, the effect of A2 type milk on lactose intolerance was improved. The first reason is that type A1 β - casein and degradation product bcm7 will aggravate lactose intolerance. Type A2 β - casein and degradation product bcm9 can improve lactose intolerance.

Research shows that yogurt, banana milk and hot milk can improve the intestinal response after eating dairy products. It is found that lactose in milk not only exists in the form of single molecule and free molecule, but also in the form of complex with other molecules, such as casein. The presence of this complex can make lactose intolerance worse.

Professor Zhu Huilian, head of Department of nutrition, School of public health, Sun Yat sen University

The development of whey protein nutrition

In the dietary guidelines for Chinese residents, the recommended amount of protein is 65g / day for men and 55g / day for women. The energy supply ratio of protein accounts for about 12% of the total energy. But in fact, the basic metabolism of the elderly is decreasing with the increase of age, and the recommended amount of energy for both men and women is decreasing gradually. However, the recommended amount of protein is 65g for men and 55g for women no matter how old they are. That is to say, when the energy demand for the elderly is decreasing, they should meet the same protein demand as the young Quantity, this seems to be particularly difficult.

The study found that the protein intake of the middle-aged and elderly people over 50 years old began to decline with the increase of age. Compared with the young people, the protein intake of the 70 year old men and women decreased by 13.2% and 12.8% respectively, that is to say, the protein intake of the old people was low. The lack of protein intake of the elderly is harmful to the health of the elderly in all aspects. One of the more important is the loss of muscle, which leads to the decline of motor function, easy to fall and fracture, and less intake of dietary nutrients, forming a vicious circle. Muscle decay is also associated with many chronic diseases.

Increasing protein intake is good for the muscle health of the elderly. The elderly with high protein intake will have 40% less muscle attenuation than the elderly with low protein intake. Muscle synthesis must have enough protein in every meal, for example, up to 25-30g. The study found that the muscle strength and muscle mass of the elderly people who ate unbalanced protein for three meals were lower than those who ate protein on average for three meals. Therefore, the elderly nutrition branch of China Nutrition Society has released the expert consensus on nutrition and exercise intervention of muscle wasting syndrome. In this consensus of experts, increasing protein intake is regarded as class a evidence of promoting muscle synthesis and slowing down muscle attenuation syndrome, and class a evidence is the strongest. In addition, in this recommendation, it is recommended that the proportion of high-quality protein per day should be 15%. Moreover, high-quality protein rich in leucine and other amino acids, such as whey protein and other animal proteins, is conducive to the muscle wasting syndrome.

Among the proteins rich in leucine or branched leucine, milk is a food source rich in branched amino acids and leucine for Chinese. Milk protein is rich in branched chain amino acids, and human muscle is also rich in branched chain amino acids, so it can provide the branched chain amino acids which are closest to the composition of muscle. Because milk protein can be digested quickly, it can provide rich essential amino acids and rich branched chain amino acids, such as leucine, etc., which are very helpful to the sports ability of the consumers.

For example, in a short-term exercise, whether before or after the exercise, whey protein supplementation, we can see that the synthesis of muscle protein is superior to other proteins.

Although it has become a consensus that nutrition and exercise are used to treat muscle attenuation in the elderly, some studies have found that the elderly are not very sensitive to resistance exercise, and even some studies have found that resistance exercise can increase some serious injuries of the elderly. For the elderly, simple resistance exercise may not be sensitive to promote the synthesis of muscle protein in the elderly. Therefore, it may be a more reasonable way to promote muscle synthesis in the elderly through nutrition, especially through protein supplementation.

In the aspect of protein supplement and promotion of muscle synthesis in the elderly, it is found that the intervention of whey protein can better increase the function of muscle in the elderly. In various food sources, leucine plays a very important role in muscle synthesis, especially for the elderly. Leucine content in whey protein is the highest. In other kinds of animal food, leucine content is about 10% or less, while whey protein can reach 14%. The muscle loss of the elderly was intervened. The elderly subjects were divided into four groups, and were given soy protein, soy protein and whey protein mixture, whey protein and control group. The results showed that the decrease rate of muscle volume in the whey protein intervention group was significantly slower than that in the control group, and the muscle function was significantly stronger than that in the control group.

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