Pasteurization makes food safe by heating microbes to death. But the high temperatures can destroy some nutrients too. A possible alternative? Ultrahigh pressure. Which may also actually increase concentrations of some nutrients, at least in tropical and subtropical fruit. That’s according to research presented at the national meeting of the American Chemical Society in Denver. [Carmen Hernandez-Brenes et al, High hydrostatic pressure processing as a strategy to increase carotenoid contents of tropical fruits]

　　In what’s called Pascalization, food is placed in a vessel, which is force-filled with water. The contents experience extreme pressures of 40,000 to 80,000 pounds per square inch. As a comparison, pressures three miles below the ocean surface are less than 7,000 pounds per square inch. The vessel’s pressure conditions kill bacteria, viruses and molds.

　　Researchers tried Pascalization on the pulp of avocados, papayas and mangos. They measured the levels of carotenoids, an important group of antioxidants. Carotenoids in the avocado and papaya increased overall by about 50 percent, with some individual carotenoids rising more than 500 percent. The mango mysteriously remained unchanged.

　　The researchers next hope to find out exactly how the high pressures are inducing the synthesis of more carotenoids. Pascalization may give food scientists plenty to chew over.

　　—Cynthia Graber

　　食物的巴氏滅菌法通過高溫殺死微生物，但是高溫同樣能夠使營養(yǎng)流失。那是否有替代方法呢?當然有，那就是超高壓滅菌。實際上，用超高壓滅菌還可以增加某些營養(yǎng)物質(zhì)，至少對于一些熱帶和亞熱帶水果，超高壓滅菌具有這樣的效果。這一理論公布于在丹佛召開的美國化學學會年會上[Carmen Hernandez-Brenes et al, High hydrostatic pressure processing as a strategy to increase carotenoid contents of tropical fruits]。

　　利用超高壓滅菌的方法稱為Pascalization。這種方法把食物裝入一個容器，然后把水壓入，注滿容器。這樣，容器內(nèi)的壓力能夠達到40000-80000磅/平方英尺。這一數(shù)字背后的壓力有多大呢?來一個對比吧。在海面下3英里的深度，水壓也不到7000磅/平方英尺。在這樣的超高壓環(huán)境下，細菌、病毒和霉菌都會被殺死。

　　研究人員利用Pascalization對鱷梨、番木瓜和芒果的果肉進行了滅菌。隨后，研究人員測定了果肉內(nèi)一類抗氧化物——類胡蘿卜素的含量。結(jié)果鱷梨和番木瓜的類胡蘿卜素總量增加了大約50%，個別種類的類胡蘿卜素增加量能達到500%。而芒果的類胡蘿卜素則保持穩(wěn)定。

　　研究人員下一步將嘗試解釋為什么超高壓能夠增加類胡蘿卜素的合成。也許，Pascalization方法不僅能夠提高食物的風味，也能吊起科學家的胃口。

　　—C