食品加工新技術課件

1、食品加工新技術課件食品加工新技術課件Introduction Each year in the food industry because of the loss caused by microbial action is huge, and produced by microbial food deterioration caused by food safety problem increasingly prominent, so the sterilization is a key process the food processing and storage. 牛牛文庫文檔分享Intr

2、oduction Each year in t Food sterilization methods varied, in terms of its essence, is the sterilization and inhibit the growth of microorganisms in food, to food can be available for use in a long time. Chemical sterilization caused serious residues of harmful chemicals in foods, 牛牛文庫文檔分享 Food ster

3、ilization methods endanger the safety of food; The traditional low temperature heating can not kill all in food microbiology, and high temperature sterilization will destroy nutrients in the food and the food in different degrees of natural features, result in nutritional components of destruction,

4、loss, or lead to bad flavor, color intensifies, loss of volatile components, etc. 牛牛文庫文檔分享 endanger the safety of food In recent years, studies have shown that ultrasonic can in a very short period of time to kill and destroy microbes, also can have on food such as homogeneous, Chen, a variety of ac

5、tion such as cracking macromolecule material, which can improve and improve the food quality and better keep food original taste and flavor, so ultrasonic technology is becoming more and more attention. 牛牛文庫文檔分享 In recent years, studies haultrasonicUltrasonic belongs to the mechanical wave, as part

6、of the sound waves, frequency is greater than 20 KHZ.Particle by mechanical force is generated by the medium effect of periodic vibration. 牛牛文庫文檔分享ultrasonicUltrasonic belongs t 牛牛文庫文檔分享 牛牛文庫文檔分享The two main parameters of ultrasonic wave: Frequency: F p 20 KHZ (similar because of the effect in pract

7、ice, usually the F 15 k of sound waves, also known as ultrasonic or higher); Power density: p = transmission power (W)/launch area (cm2); Usually p acuity 0.3 w/cm2; 牛牛文庫文檔分享The two main parameters of ultltrasonic wave has the following features: 1) ultrasound can be in gas, liquid and solid, solid

8、solution and other effective transmission medium. 2) ultrasound can pass strong energy. 3) the superposition of ultrasonic will produce reflection, interference, and resonance phenomenon. 4) the spread of ultrasound in liquid medium, can have a strong impact on the interface and cavitation phenomeno

9、n. 牛牛文庫文檔分享ltrasonic wave has the followiUltrasonic effect when the ultrasonic wave propagation in the medium, because of the ultrasonic wave interaction with the media, physical and chemical changes in the medium, to produce a series of mechanical, thermal, electromagnetics and chemical effects of

10、ultrasound, including the following four kinds of effects: 牛牛文庫文檔分享Ultrasonic effect when the ult(1) mechanical effect. Ultrasonic mechanical action may contribute to a liquid emulsion and the liquid and solid dispersion of gel. When ultrasonic standing wave formed in the fluid medium of particles s

11、uspended in a fluid due to the effect of mechanical force and condensed in nodal, 牛牛文庫文檔分享(1) mechanical effect. www.niu Ultrasonic wave propagation in piezoelectric materials and magnetostrictive materials, due to the mechanical action of ultrasonic wave caused by the induced polarization and elect

12、ric induced magnetization (see the dielectric physics and magnetostriction). 牛牛文庫文檔分享 Ultrasonic wave propagation(2) Cavitation effect(3) heat effect Due to the ultrasonic frequency is high, the energy is large, when absorbed by the medium can have a significant effect. 牛牛文庫文檔分享(2) Cavitation effect

13、www.niuwk(4) chemical effect The role of ultrasound can make or speed up certain chemical reactions happen. For example, the pure distilled water after ultrasonic treatment to produce hydrogen peroxide; Water is dissolved nitrogen after ultrasonic treatment produce nitrite; Dye 牛牛文庫文檔分享(4) chemical

14、effectwww.niuwk.c aqueous solution after ultrasonic treatment can change color or fade. The occurrence of these phenomena with cavitation accompanied. Ultrasound can also accelerate the hydrolysis of many chemical substances, decomposition and polymerization process. Ultrasonic light chemical and el

15、ectrochemical process 牛牛文庫文檔分享 aqueous solution after ultr has obvious influence. Various amino acids and other organic material solution after ultrasonic treatment, the characteristic absorption spectrum with disappear and general absorption of homogeneously, this shows that the cavitation effect m

16、akes the molecular structure has changed. 牛牛文庫文檔分享 has obvious influence. VariMechanism of ultrasound sterilizationCavitation effect Ultrasonic cavitation is refers to the tiny air bubbles in the liquid core vibrate under the wave action, when the pressure reaches a certain value, the cheongsam will

17、 rapidly expand, then suddenly closed, the bubbles have repercussions when closed, this expansion, closure, oscillation and a series of dynamic process called ultrasonic cavitation. 牛牛文庫文檔分享Mechanism of ultrasound steril 牛牛文庫文檔分享 牛牛文庫文檔分享 牛牛文庫文檔分享 牛牛文庫文檔分享The influencing factors of ultrasonic cavita

18、tion: (1) ultrasonic intensity Ultrasonic intensity refers to the ultrasonic power per unit area, have related to the intensity of the ultrasonic cavitation. For general liquid ultrasonic intensity increases, 牛牛文庫文檔分享The influencing factors of ult the cavitation intensity increases, but after reachi

19、ng a certain value, cavitation tends to saturation, at this time in increasing the intensity of ultrasonic, can produce a large number of useless bubbles, thus increasing the scattering attenuation, reduce the intensity of cavitation. 牛牛文庫文檔分享 the cavitation intensity in (2) ultrasonic frequency Ult

20、rasonic frequency is lower, the easier to produce cavitation in the liquid. That is to cause cavitation, the higher the frequency, the greater the need sound intensity. Generally USES the frequency range of 20-40 KHZ. 牛牛文庫文檔分享 (2) ultrasonic frequencywww (3) the surface tension of the liquid and vis

21、cous coefficient The greater the surface tension of liquid, cavitation intensity is higher, the more it is not easy to produce cavitation. Viscous coefficient of liquid is difficult to produce cavitation bubble, and losses in the transmission of large, so also is not easy to produce cavitation. 牛牛文庫

22、文檔分享 (3) the surface tension of (4) the temperature of the liquid Liquid temperature is higher, the better in the formation of cavitation, but at high temperature, air bubbles in the vapor pressure increases, thus enhances the cushion makes the cavitation bubbles closed. 牛牛文庫文檔分享 (4) the temperature

23、 of the It is generally believed that ultrasound have the sterilization effect is mainly caused by its produce cavitation. Tiny bubbles at the instant of the adiabatic compression and collapse, 牛牛文庫文檔分享It is generally believed that its internal can present above 5000 high temperature and the pressur

24、e of 50000 kpa, thus kill some bacteria in the liquid, and virus inactivation, and even some small microbial cell wall broken, but their range is limited. 牛牛文庫文檔分享 its internal can present abThe influence of ultrasonic sterilization effect factorsUltrasonic effect parametersMicrobial propertiesOther

25、 factors 牛牛文庫文檔分享The influence of ultrasonic stUltrasonic effect parametersSound intensity General situation of sterilization intensity is 2 to 10 w/cm2; When the sound intensity exceeds a certain limit, cavitation effect will weaken, sterilization effect will decline. 牛牛文庫文檔分享Ultrasonic effect para

26、meterswwFrequency Sterilization of ultrasound for 20 to 50 KHZ frequency; With the increase of frequency, sound wave propagation attenuation will increase, the sterilization effect will be reduced. 牛牛文庫文檔分享F 牛牛文庫文檔分The amplitude In general amplitude increase bactericidal effect will also be enhanced

27、. 牛牛文庫文檔分享The 牛牛文The sterilization time Research has shown that with the increase of the sterilization time, sterilization effect is generally higher than increase, but to further increase the sterilization time, sterilization effect and no obvious increase, but tend to be a saturated value. So the

28、general sterilization time is set within 10 minutes. 牛牛文庫文檔分享The sterilization timewww.niuwMicrobial propertiesThe concentration of bacteria in the sample When the sterilization time phase at the same time, the samples contain high concentrations of bacteria sterilization effect is slightly less tha

29、n when low concentration. 牛牛文庫文檔分享Microbial propertieswww.niuwk.The capacity of bacteria in the sample Ultrasonic wave exists in the process of media transmission attenuation phenomenon, will increase with the increase of propagation distance and, therefore, with the increase of sample processing, s

30、terilization effect would be reduced. 牛牛文庫文檔分享The capacity of bacteria in thMicrobial species The effects of ultrasound on microbial with state of the structure and function of microorganisms in itself. Generally speaking, the killing effect of ultrasound on the microorganisms is kill bacillus is fa

31、ster than kill bacteria; For big coli faster than small bacillus kill. 牛牛文庫文檔分享Microbial Other factors Sterilization, sample temperature can also affect the sterilization effect of temperature, ultrasonic effect on the destruction of the bacteria. Ultrasound in different coal quality, effects on dif

32、ferent components of the food, the effect will be different. Lopez - Malo, etc. 牛牛文庫文檔分享Other 牛牛文 The effects of pH, water activity, temperature and ultrasonic amplitude of finger mold bactericidal effect, found the water activity in 0.99, adding ultrasonic amplitude and lower pH can reduce D value;

33、 When pH values, water activity increased when D value decreased. 牛牛文庫文檔分享 The effects of pH, water acUltrasonic sterilization technologyIn the early 1930 s, ultrasonic and collaborative research on other means of sterilization has been put forward. Some results show that the single use of ultrasoun

34、d sterilization effect is limited, but the ultrasound combined with other sterilization methods, has great potential, its sterilization effect is very significant. 牛牛文庫文檔分享Ultrasonic sterilization technUltrasonic sterilization aloneSoy sauce is a liquid by microorganism fermentation and get food, it

35、 is in the process of production easy to be contaminated with harmful bacteria, mold, etc, when the temperature above 20, white spots appear easily in the soy sauce surface, then upset, will form the wrinkled film, color from white to brown, this is the soy sauce mildew, mildew soy sauce concentrati

36、on, 牛牛文庫文檔分享Ultrasonic sterilization alone freshness, nutrition is mixed bacteria consume, seriously affecting the quality of soy sauce. The manufacturers generally use the antibacterial, such as preservatives or heat sterilization measures. Preservative bacteriostasis will remain some harmful ingre

37、dients to human body, at the same time, still have a kind of bad taste, greatly reduces the quality of soy sauce. And heating sterilization is not only consumes a lot of 牛牛文庫文檔分享 freshness, nutrition is mix energy, and inevitablyconsume soy sauce ingredients. Ultrasonic sterilization technology appl

38、ied to soy sauce preservation is to overcome these problems. With soy sauce has a basic characteristics of ultrasonic processing, it is a fall in its viscosity, colour and lustre is becoming clear. 牛牛文庫文檔分享 energy, and inevitablyconsuGreen tea drinks in the machining process, due to reasons such as

39、the oxidation of tea polyphenols, color is darker, by initially yellowish gradually become brown, namely Browning, which makes the appearance of green tea beverage and drinks quality severely affected. Using ultrasonic wave to the beverage sterilization 牛牛文庫文檔分享Green tea drinks in the machin can be

40、well keeping tea polyphenol content in tea soup, is conducive to the stability of tea liquor color and transparency, sterilization and protection of tea is green tea polyphenols against losses as far as possible make it has good colour and lustre is a good tea processing technology. 牛牛文庫文檔分享 can be

41、well keeping tea polUltrasonic sterilization technology is a kind of cold sterilization technology, compared with traditional high temperature heating sterilization technology, ultrasonic action does not change the food color, aroma, taste, can well protect the colour and lustre of juice drinks. Ult

42、rasound (500 KHZ, 500 w) was used for orange juice was studied, under the action of ultrasonic, limonin, 牛牛文庫文檔分享Ultrasonic sterilization techn brown pigment in orange juice without adverse effect upon product quality, the results show that the limonin in orange juice content did not change, also no

43、t Browning and color changes. Ultrasound applied to the processing of lemon juice, lemon juice tastes and the nutrient damage of colour and lustre, and obtained good effect. 牛牛文庫文檔分享 brown pigment in orange juiUltrasound with other technologies synergistic sterilizationUltrasonic sterilization is ch

44、aracterized by fast speed, no external additive, harmless to human body, no damage to items. But the sterilization effect is not completely, still is mainly used for secondary sterilization. If want to further improve the efficiency of sterilization, the ultrasonic must be used 牛牛文庫文檔分享Ultrasound wi

45、th other technolo in combination with other sterilization technology together. Here is in recent decades, the synergy of ultrasound with other technologies in the research of sterilization: (1) Ultrasonic synergy ozone (2) Ultrasonic synergy nano titanium dioxide 牛牛文庫文檔分享 in combination with other s (3) Ultraso