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養耕共生澳洲電台專訪

Aquaponics an answer to Pacific's food security
Updated October 12, 2011 11:07:35
養耕共生是太平洋環帶地區的食物危機的最佳解決方案
The chronic water shortage in Tuvalu, Tokelau and the Samoas is raising concerns that some islands may face widespread crop failures. But marine and aquaculture researchers say there is a way to tackle the food and water crises. Aquaculture specialists in American Samoa say the use of aquaponics to grow fruit and vegetables could lead the way to future food security.

主持人: Geraldine Coutts
主講者: Ephraim Temple, the Sea Grant program coordinator at American Samoa's Community College

TEMPLE: Aquaponics is where you grow fish and plants in the same water, so as you feed the fish, they produce waste and the waste is used by the plants as fertiliser, so the water is recycled over and over to raise both fish and plant crops.

COUTTS: Even though it's efficient and economic when it comes to the use of water and the amount of water. Isn't this also too much water what given the crisis that's happening in a number of the nations at the moment?

TEMPLE: If you look at the literature for the amount of water that's required by traditional farming in soils, compared with the amount of water used for producing crops and aquaponics, you find that's about ten times less water usage in aquaponics. And so one could argue that it does use water conservatively and less than growing in traditional farming. So places that have little water, this is actually an ideal way to produce crops, because your recycling the water over and over. So may be initially to fill your tanks, then you do need as much water as your tank sizes are, but after that, then it requires very little to maintain the system.

COUTTS: And what about sort of bugs in the water and pollution, does that need to be filtered out so it doesn't devastate the crops that your trying to grow?

TEMPLE: In traditional aquaculture, where you have either ponds or tanks and you're raising higher quantities of fish. You have to deal with effluent that is full of nitrogen and that can be a problem. The beauty of aquaponics is the waste that's coming from the fish is actually taken up by the plants in that same system and so you have little to no run off to begin with, because the waters recycled and any run off that you do have has very low pollution in it as far as excess nutrients. So that's really the beauty of the system.

COUTTS: Well, your colleagues, the American Samoa Community College in partnership with the University of Hawaii will be hosting a workshop next week on building aquaponics capacity. How can you build the capacity, is it just having more tanks right throughout the region?

TEMPLE: Sure, that's one way. Another way is just giving people options. If they know that this is something available to them, that you can raise crops this way, then more people will be willing to go there. People often think that farming isn't for them, that their land is to full of sand or coral or to uneven, but aquaponics opens the door to growing, for people to have gardens in their backyards where those conditions are present. So I think if that is an option to them and they're understanding it, they will adopt that type of farming and start raising their own crops. That then improves their food security as well as conserves their water - producing this food that they're raising themselves.

COUTTS: Because no soil is required?

TEMPLE: That's right, that's right. So on many of these low lying atolls, the soil is poor to begin with, and most of the food is raised in the inner most part of the atoll, where they've kind of made a soil. But in this with aquaponics, people living right along the shore, they can build a small farm and they don't need soil at all.

COUTTS: Alright, to what extent could the food security be boosted using this method, aquaponics?

TEMPLE: That's a tricky question. I don't know if the economics of that have been analysed closely. But if every family were to establish their own aquaponic system, just on a small footprint of may be 30 square feet, you could produce all your plant food for your family. So that's really a small footprint and then you're relying solely on yourself to produce your food. Then you'd have to look elsewhere for your proteins, but at the same time, you know that you're raising fish in your systems as well. So as long as you're harvesting fish and plants, you're basic nutrition is covered. If you need specialty items, then that would have to come off island.

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菜豆

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黑檸檬

黑檸檬
Dried lemons are actually limes and are used heavily in Persian Gulf and also Iranian cuisine where they add a strong bitter flavor in addition to sourness. They are made by boiling ripe limes in salt water, and then sun drying until the insides turn black. The outside color varies from tan to black. They are sold whole or ground.

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為何冰箱冷凍室非得是零下18度?

為何冰箱冷凍室非得是零下18度? 不少家庭的冰箱有led面板,可顯示冷藏室和冷凍室溫度。每次看到那個零下18℃,不少人,包括筆者在內就會禁不住提出一個小疑問:為什麼冷凍室溫度非得是零下18℃?最多零下1℃不就結冰了嗎?搞這麼低溫度實在是浪費電呢。

聰明如很多人是這樣推測的

百思不得其解,於是很多人,包括筆者在內就開始推測後面的機制了。冷凍室的零下18℃其實不費電,相反,它是節約電力的一個好措施。為何?

冰箱隔一段時間,內部溫度升高後,它就要啟動壓縮機,嗡嗡嗡的。頻繁啟動壓縮機不僅耗電,冰箱的壽命也會降低,還有就是很吵人。怎麼辦?簡單,先把冷凍室的溫度搞得低低的,比如零下18℃左右。


然後,冷凍室的冷氣往上走,來到冷藏室,如此,就能長時間保持冷藏室的溫度處於0到8℃以內了。

待冷凍室的冷氣散失過多,溫度升高到零下幾度時,再啟動冰箱的壓縮機把溫度再次降到零下18℃,如此,冰箱的啟動次數就變少了。

實際是這樣嗎?很遺憾,不是。

原因之一:不一樣的水

水到零度以下就結冰了,這是絕大多數人的認識。然而仔細一想,這不適用於冰箱的冷凍室。因為冷凍室存放的不是上百升礦泉水,而是各種各樣的食物。

食物中含有大量水這沒錯,但這些水同時含有大量的鹽、糖等物質。就像每1升海水中大約含有35克鹽,所以平均起來,要到零下1.33℃時海水才會結冰。

因此,要想把食物凍結,並不是溫度只要達到水的冰點就可以,得保證足夠低的溫度,食物中的水才能凍結,這很重要,因為食物中只要有液態水存在,這就等於是為各種細菌的繁殖提供了必備條件。

圖為牛肉薄片在不同溫度和不同時間內測得的牛肉中凍結水量的曲線。

當牛肉薄片的溫度為零下4℃時,只有70%的水分被凍結;溫度下降到零下9℃左右時,也還有3%的水分未凍結;即使牛肉薄片的溫度降低到零下18℃時,也不是100%的水分都被凍結住。

原因之二:嗜冷微生物

根據微生物對不同溫度的適應範圍,可將微生物分為三大類,嗜熱菌、嗜溫菌和嗜冷菌。在食物的冷藏和冷凍過程中,我們面對的「敵人」是嗜溫菌和嗜冷菌。

一般來說,能引起食物腐敗和食物致毒的嗜溫菌,在低於3 ℃情況下不產生毒素,當然,個別菌種例外。

而對於嗜冷菌,一般得在零下10 ℃到零下12 ℃時才會停止生長。

有的黴菌甚至要到零下15~零下18 ℃時才會停止生長。

瞧,我們以為,零下幾攝氏度後微生物就被殺死或停止繁殖了,但…