標題: 飼料在生產過程中產生的氣味 [打印本頁] 作者: monica 時間: 2007-12-24 17:52 標題: 飼料在生產過程中產生的氣味 Processing
Feed raw materials sometimes have a pleasant smell, such as by-products from the fruit juice industry. But products can also have a foul odour, especially when oils and fats are involved or products are treated by pressure and temperature.
To avoid complaints of residents around a feedmill these smells need to be neutralised.
The oxygen used is directly extracted from the outside air by means of a blower and then filtered before it enters the injector.
(Photo: Aerox) Many factors determine whether an odour is pleasant or not, even human perception can
be different to the same odour. The main reason for this subjective perception is because odour can be imagined as a cocktail of possibly hundreds of different organic components and not as just one sin-gle molecule that determines the smell. The weight concentration is mostly very low, but the odour-con-centration (=number of required dilution).
The odour-components with the lowest concentra-tions (sub-ppb-range) cannot be detected by laboratory equipment, but the human nose could very well notice them. So the main reason for a factory or feed plant to do something about odour reduction is the
sensitivity of the noses of the people that live in the vicinity of the plant. This also complicates the matter, because it is impossible to make calculations or pre-dictions on odour-emission. Each odour-component can mask or amplify another component within the cocktail. Odour is dynamic, since the components and their concentrations will vary in time due to differences in process- conditions, raw materials, weather-conditions, etc.
Nothing beats the nose
Paticles can generate odour once they are released in atmosphere, especially particles below 1 micron have a large total surface area. The human smell, although less sensitive than that of other mammals, is a source of information about chemical substances in the environment. Our nose is capable of recognising up until 4,000 smells at very weak concentrations in smelling molecules. Analytical techniques do not always succeed in reaching such a threshold in smelling molecules.To measure a smell, the best instrument still remains the nose with its olfactive mucous, which is a really reliable sensor. The stenches generated by industrial activities contain between 200 and 800 different active substances. The most frequent are sulphur-containing molecules in the smell of rotten eggs, nitrogenous molecules (such as ammonia) and ketones and aldehydes, which cause bitter and rancid smells. The human vocabulary can not exactly define a smell as it can describe a colour, but Table1tries to sum up what can be smelled from different molecules.
Molecule(s) Association smell
Hydrogensulphide Rotten eggs
Mehtylmercaptan Cabbages
Ethylmercaptan Rotten cabbages
Allylmercaptan Garlic
Ammonia Very prickly,irritating
Methylamine Rotten fish
Indole,scatole Excrement
Cadaverine Decaying meat
Acetic acid Vinegar
Butyric acid Rancid butter
Valeric acid Sweat,perspiration
Fomaldehyde Acrid,close
Acetaldehyde Fruit,apple
Acetone Sweet fruit
Dimethylsulphur Decomposing vegetables
Thiolane Gas (product for odourisation of gas)
Olfactometry
It is impossible to calculate odour reduction efficiencies without olfactometric measurements. Olfactometry allows to quantify the concentration of a smelling mixture and to determine the intensity of it. What factually happens is that a sample of air is taken directly from he outlet and in a laboratory is diluted with clean air.A panel of trained people smell the most diluted samples first and continue with smelling samples that are less diluted. As soon as 50% of the panel detects a smell,this is considered to be the odour detectability threshold referring to the minimum concentration that produces an olfactory response or sensation.There are several odour thresholds that can be determined using olfactometry. They are: The detection threshold, which is defined as the lowest concentration that will elicit a response without reference to odour quality. This is reproducible and the most widely reported odour measurement in literature. The recognition threshold is defined as the minimum concentration that is recognised as having a characteristic odour quality. The description threshold is the point at which the panellist is asked to distinguish the odour.
[ 本帖最后由 monica 于 2007-12-24 17:54 編輯 ]作者: 張安弟 時間: 2007-12-24 21:29
我提過見議:以后發帖子,盡量把英文翻譯成中文,因為每個人的文化水平都不可能與你一樣高.作者: hn-mzj 時間: 2007-12-24 23:17
^_^，這里可是專業英語版塊！是讓大家學英語的，當然因該讓有興趣的朋友來翻譯了！作者: monica 時間: 2007-12-25 08:42
翻譯是很一件很不容易的工作，費時費力，希望能有更多的人加入進來。同時也向論壇以前發過翻譯文章的所有朋友致意。作者: wning 時間: 2007-12-25 11:21 Processing
Feed raw materials sometimeshave a pleasant smell, such as by-products from the fruit juiceindustry. But products can also have a foul odour, especially when oilsand fats are involved or products are treated by pressure andtemperature.
有時候某些飼料原料的氣味會比較宜人，比如果汁業的副產物就是如此。不過也有些副產物飼料具有難聞的氣味，尤其是當其中所含的油脂出問題或者是用壓力和溫度處理的時候，更是易出現氣味的問題。
To avoid complaints of residents around a feedmill these smells need to be neutralised.
The oxygen used is directlyextracted from the outside air by means of a blower and then filteredbefore it enters the injector.
為了避免對飼料廠附近的居民造成不良影響，副產品飼料加工過程中出現的各種氣味都有必要進行消除處理。處理所用的氧氣用風箱從工廠外提取，然后在其進入注入器之前經過過濾處理。
(Photo: Aerox) Many factors determine whether an odour is pleasant or not, even human perception can
be different to the sameodour. The main reason for this subjective perception is because odourcan be imagined as a cocktail of possibly hundreds of different organiccomponents and not as just one sin-gle molecule that determines thesmell. The weight concentration is mostly very low, but theodour-con-centration (=number of required dilution).
飼料原料最終氣味的好與壞由許多因素來決定，甚至不同的人對同一種氣味的感覺也是不同的。這種主觀感覺差異的主要原因是由于氣味并不僅僅是由一種單一的分子所決定，你可以想象一下一種雞尾酒，其氣味可能是由數百種有機成分而不是一種所產生的。
The odour-components with thelowest concentra-tions (sub-ppb-range) cannot be detected by laboratoryequipment, but the human nose could very well notice them. So the mainreason for a factory or feed plant to do something about odourreduction is the
sensitivity of the noses ofthe people that live in the vicinity of the plant. This alsocomplicates the matter, because it is impossible to make calculationsor pre-dictions on odour-emission. Each odour-component can mask oramplify another component within the cocktail. Odour is dynamic, sincethe components and their concentrations will vary in time due todifferences in process- conditions, raw materials, weather-conditions,etc.
濃度最低（十億分之一以下范圍）的氣味成分不能被實驗設備檢測到，但是人類的鼻子卻能非常清楚的感覺到它們。因此一個工廠或者飼料廠需要做些減輕氣味的工作主要是由于廠子附近居民的鼻子對氣味有很高的感受性。這也使得問題變得復雜了，因為不可能對氣味的排放進行計算和預測。總氣味成分中的每一種氣味成分可以掩蓋或者增強另一種氣味成分的氣味。氣味是呈動態變化的，這是由于各氣味成分和它們的濃度會由于加工條件、原材料、天氣情況等等的不同而隨時間而變化。
Nothing beats the nose
Paticles can generate odouronce they are released in atmosphere, especially particles below 1micron have a large total surface area. The human smell, although lesssensitive than that of other mammals, is a source of information aboutchemical substances in the environment. Our nose is capable ofrecognising up until 4,000 smells at very weak concentrations insmelling molecules. Analytical techniques do not always succeed inreaching such a threshold in smelling molecules.To measure a smell, thebest instrument still remains the nose with its olfactive mucous, whichis a really reliable sensor. The stenches generated by industrialactivities contain between 200 and 800 different active substances. Themost frequent are sulphur-containing molecules in the smell of rotteneggs, nitrogenous molecules (such as ammonia) and ketones andaldehydes, which cause bitter and rancid smells. The human vocabularycan not exactly define a smell as it can describe a colour, butTable1tries to sum up what can be smelled from different molecules.
什么東西都敵不過鼻子
物質的微小顆粒一旦釋放入空氣中就會產生氣味，特別是對粒徑在一微米一下的顆粒而言，由于總表面積巨大，所產生的氣味更為強烈。人的嗅覺雖然比其他的哺乳動物要遲鈍，但也是獲取環境中化學物質信息的一種途徑。在各種氣味分極低的濃度下，我們的鼻子能夠辨別出它們所產生的多達4000種氣味。氣味分析技術有時也不一定能達到探測出如此眾多的氣味分子的水平。為了測量一種氣味，最好的儀器仍然是鼻子的嗅粘膜，它的確是非常可靠的感應器。工業生產活動產生的惡臭氣味由200至800種不同的活性物質所產生。其中最常見的是有臭雞蛋氣味的含硫氣體分子、含氮氣體分子（如氨）和丙酮及乙醛，后面這些氣體則產生苦味和腐臭味。人類的語言詞匯不能像描述一種顏色那樣準確的去定義一種氣味，不過在表一中我們試圖總結一下從不同的氣體分子中我們可以聞出什么。
Olfactometry
It is impossible to calculateodour reduction efficiencies without olfactometric measurements.Olfactometry allows to quantify the concentration of a smelling mixtureand to determine the intensity of it. What factually happens is that asample of air is taken directly from he outlet and in a laboratory isdiluted with clean air.A panel of trained people smell the most dilutedsamples first and continue with smelling samples that are less diluted.As soon as 50% of the panel detects a smell,this is considered to bethe odour detectability threshold referring to the minimumconcentration that produces an olfactory response or sensation.Thereare several odour thresholds that can be determined using olfactometry.They are: The detection threshold, which is defined as the lowestconcentration that will elicit a response without reference to odourquality. This is reproducible and the most widely reported odourmeasurement in literature. The recognition threshold is defined as theminimum concentration that is recognised as having a characteristicodour quality. The description threshold is the point at which thepanellist is asked to distinguish the odour.
氣象色譜
沒有氣象色譜的測量就不可能計算減輕氣味措施的效率。氣象色譜可以用來測量一種氣體混合物的濃度，并且還可以測定氣味的強度。具體的過程是先直接從氣體出口采集氣體樣品，讓后講樣品在實驗室用清潔的空氣稀釋。一旦有50％的顯色板檢測到一種氣味，這時的氣體濃度就可以看作是能夠檢測出該氣味的閾值，也就是可能產生一種嗅覺反應或者感覺的最小濃度。可以用氣象色譜測定幾種氣味濃度閾值。它們分別是：檢測閾值，它被定義為能夠明確的對某種不能說出性質的氣味產生反應的最低濃度。這是已有文獻中具有可重復性和最廣泛報道的氣味測量；辨別閾值被定義為能被辨別具出特有氣體性質的最小濃度。描述閾值為色譜板操做人用來辨別氣味的濃度值。
