Nostoc flagelliforme and faked items retailed in Hong Kong

Paul Pui-Hay But*, Ling Cheng, Pui Kwan Chan, David Tai-Wai Lau and Joyce Wing-HinButDepartment of Biology and Institute of Chinese Medicine, The Chinese University of Hong Kong, Shatin N.T.,Hong Kong, P.R. China; *Author for correspondence (e-mail: paulbut@cuhk.edu.hk; phone: +852-2609-6299;fax: +852-2603-5646)

Received 30 June 2001; accepted in revised form 8 August 2001

Key words: Adulteration, Conservation, Fat Choy, Nostoc flagelliforme, Starch

Abstract

A survey was made to check the authenticity of both dried and cooked Nostoc flagelliforme retailed as Fat Choyin Hong Kong, using microscopic and histochemical methods. Results indicated that faked items were found in70% of the 30 samples of dried Fat Choy retailed in seafood stores and herb shops and in all 5 samples ofcooked Fat Choy obtained from Chinese restaurants. The faked items were non-cellular and packed with starchgrains or masses and black pigments. Staining the faked items with iodine solution turn them into dark blue orblack, whereas the genuine samples remained dull greenish. This widespread adulteration probably reflects thelimited supply of this alga which is banned in China from further collection and trading.

In Chinese cuisine, ‘Fat Choy’ in Cantonese or ‘FaCai’ in Mandarin refers to a black hair-like delicacy,often served in Chinese foods during festive seasonssuch as the Chinese Lunar New Year. It does not lookappealing and is tasteless but would carry the taste ofthe gravy in the dish. It is taken as a food item mainlybecause the name ‘Fat Choy’ or ‘Fa Cai’, which lit-erally means hair vegetable, reads the same as ‘strikea fortune’, as one would find in such Chinese greet-ings as ‘Kung Hei Fat Choy’ – wishing you the luckto strike a fortune.

The hair vegetable is Nostoc flagelliforme (Berk etCurtis) Bornet et Flahault, a blue-green alga belong-ing to the family Nostocaceae. Its filaments aregrouped together as macroscopically recognizablestrands by a gelatinous sheath. Individual strands ap-pear dull greenish when wet, but dried bundlesstacked on one another give a black hair-like appear-ance. This alga grows very slowly in desert steppeand bare areas in arid and semi-arid regions in north-ern and north-western China, and binds to the sub-stratum there (Diao 1996).

The use of N. flagelliforme as a delicacy was al-ready documented in the Jin Dynasty around 300A.D. (Gao 1998). Demands for it kept increasing in

the last two decades, when the Chinese economy en-tertained rapid growth (Geng and Jiang 1991). Effortswere invested to propagate and grow this alga in itsnatural habitat in China, (Dai 1992; Diao 1996; Gao1998; Gao and Yu 2000), but were met with hardlyany success (Shi 1986; Cao et al. 2001). Over exploi-tation of this alga, on the other hand, has seriouslydamaged extensive ranges of vegetation in northernand northwestern China. As a consequence, the StateCouncil of the People’s Republic of China announcedin June 2000 to prohibit further collection and trad-ing of Nostoc flagelliforme, so as to halt the progressof desertification in northern China. Since then, theprice of Fat Choy kept increasing. Market samples inHong Kong now fetch about US$2–8 for each 30 g.Consumers, however, keep complaining and suspect-ing that faked items are flooding the market.

In collaboration with the Consumer Council inHong Kong, we made a survey of 30 samples of FatChoy retailed in seafood stores and herb shops inHong Kong as well as five samples of Fat Choy infoods served in Chinese restaurants in Hong Kong(Consumer Council 2001).

Dry samples of Fat Choy were first soaked inwarm water for 10–30 minutes, while those from res-

143Journal of Applied Phycology 14: 143–145, 2002.© 2002 Kluwer Academic Publishers. Printed in the Netherlands.

Note

taurants were first washed in warm water to rinse offthe gravy. A few strands were taken from the soakedsamples and placed on a glass slide. For microscopicanalysis, these strands were cut longitudinally orground to loosen the gelatinous sheath. A little pres-sure was added, if necessary, to further expose thefilaments of bead-like cells. The specimens were thenexamined under the light microscope. For histochem-ical analysis, strands from the soaked samples wereplaced on a glass slide and stained with iodine solu-tion. They were then inspected under daylight oragainst daylight. The iodine solution was prepared bydissolving potassium iodide 0.5 g and iodine 1 g in100 mL of distilled water. The testing solution wasmade by diluting 10 mL solution to 40 mL with dis-tilled water.

In the 35 samples (Table 1), two types of materi-als were found, but they look very similar in size(0.2–1 mm.diameter) and color (black). The first typewas genuine strands of Nostoc flagelliforme, whichshowed under light microscope the typical filamentsof bead-like cells embedded in a gelatinous sheath.The second type was strands of non-cellular material,which appeared under light microscope as opaquetubes packed with starch grains or masses and blackpigments. The cooked strands obtained from restau-rant dishes, on the other hand, appeared as somewhathomogeneous and translucent tubes without anybead-like cells but sparingly bearing isolated starchgrains. These non-cellular strands are consideredfaked items in this report. When individual strands ofthe soaked samples were placed on a glass slide orglass plate, stained with iodine solution, and exam-ined against daylight, the genuine materials wouldremain dull greenish, whereas the faked items wouldturn dark blue or black, mainly due to the starch inthe faked items.

Among the 30 dried samples (Table 1), nineshowed the presence of only genuine N. flagelliforme.Another nineteen samples contained mixtures of bothgenuine N. flagelliforme and faked items, the percent-age of faked items varying from 2–90%. The remain-ing two samples contained only faked items. Besides,all five restaurant samples were a mixture of genuineN. flagelliforme and faked items. The percentage offaked items in these dishes, however, was not deter-mined because they were dispersed among differentparts of the dishes.

Results of this survey confirmed that N. flagelli-forme remains a common delicacy in Hong Kong andalso revealed that 70% of the dry samples of Fat Choy

retailed in Hong Kong and all the cooked samplesobtained from restaurant dishes were adulterated withstarchy strands. An adulterant of possibly starchy na-ture was also found in Inner Mongolia (Cao et al.2001). This widespread adulteration is unfair to con-sumers. To protect consumer rights, suppliers, tradersand retailers of Fat Choy should clearly declare anysubstitute in their products – as in the case of veg-etarian abalone or shark fin imitate. Also any N.flagelliforme substitute or imitate should not containhazardous substance such as banned color additives.

Table 1. Authenticity of Fat Choy retailed in Hong Kong (samples1–30 were obtained dry; samples 31–35 were samples from foodserved in restaurants)

Sample Claimed origin Faked item

1 China 0%

2 Inner Mongolia 0%

3 Gansu 0%

4 Hebei 0%

5 Qinghai 0%

6 Gansu 0%

7 Gansu 0%

8 Gansu 0%

9 Qinghai 0%

10 Gansu 2%

11 Qinghai 5%

12 Not known 15%

13 Ningxia 10%

14 Hebei 10%

15 Gansu 10%

16 Gansu 35%

17 Gansu 40%

18 Inner Mongolia 45%

19 Gansu 45%

20 Inner Mongolia 50%

21 Inner Mongolia 60%

22 Inner Mongolia 60%

23 Hebei 70%

24 Gansu 70%

25 Inner Mongolia 20%

26 Gansu 85%

27 Gansu 85%

28 Gansu 90%

29 Not known 100%

30 Gansu 100%

31 Not known present

32 Not known present

33 Not known present

34 Not known present

35 Not known present

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On top of consumer protection, it should be notedthat the widespread adulteration of Fat Choy in HongKong could be a reflection of the limited supply of N.flagelliforme. Clearly, N. flagelliforme is neither a sta-ple food nor an important herbal medicine in China.It is consumed occasionally as a delicacy in Chinesefood simply because its name reads the same as thewish for striking a fortune. This practice is consideredcute by users, but hardly anyone taking the algawould care to think of its value as a good wish.Rather, the continual collection of this alga wouldhave detrimental impact on the environment. Therapid progress of desertification in northern andnorthwestern China has prompted the Chinese gov-ernment to ban further collection and trading of N.flagelliforme. In view of the current political andbusiness situation as well as the difficulty in growingN. flagelliforme in northern and northwestern China,the future prospect of producing this alga in its natu-ral habitat in China looks gloomy. Researchers andtraders should be aware of the issues concerned andmake appropriate plans and strategies.

Acknowledgements

Partial support was received from Innovation andTechnology Fund AF/181/97 and AF/281/97, Innova-

tion and Technology Commission, Government of theHong Kong Special Administrative Region, and fromConsumer Council, Hong Kong.

References

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