FOOD is usually preserved by curing – in salt or a salt solution (brine) – and removing the moisture. The way lap mei is produced is similar to the western way of producing, say, cured ham and chorizo sausages.
In the past, the cured meats were air-dried in the cold and dry northern winds that blew from high latitude areas at this time of year in China.
Today, they are mostly produced in highly regulated factories under controlled conditions. As its production is now not subjected to the vagaries of inclement weather, they can be produced year-round and in a much shorter span of time, but the demand for lap mei traditionally peaks around the spring festival.
According to a report published by the Hong Kong government, the process involves five main steps: the raw materials, usually meat or duck, are cleaned and cut. They are then placed in a curing mix of salt, sugar, wine, and nitrate, either manually or mechanically.
The mixture is then placed in chillers overnight to allow stabilisation and thorough diffusion. Some manufacturers may add other flavouring agents such as spices or soya sauce, and food additives such as colouring to enhance the appearance and taste of the products.
After curing and seasoning, the ingredients have to be dried to bring the moisture content down to 25% or lower. In the industrial setting, this is done via hot air drying in chambers at between 35°C and 40°C, for three to four days for the preserved sausages.
The addition of nitrates
The addition of nitrate or nitrite to meat at low concentrations has become common practice in the preservation of meat around the world for centuries. The nice, rosy pink appearance of cured meats such as ham and sausages is due to the addition of nitrate salt and/or nitrite in the production process.
If cured meats are not produced with nitrate, they will have an unappetising grey cloak, so that pinkish-red lap cheong will be greyish and quite dull – something that most consumers will not be able to accept.
In the curing of lap mei, nitrate/nitrite is essential not only to provide a unique characteristic colour, but also taste and texture, and more importantly, is its anti-microbial properties against bacteria growth and spore formation especially that of Clostridium botulinum, according to the 1999-2000 Lap Mei Surveillance Report by the Food and Public Health Branch of the Food and Environmental Hygiene Department of the HKSAR government.
The research was commissioned to explore the health implications of lap mei consumption as nitrites may react with other substances found in meat forming nitrosamines, compounds that could cause cancer.
An earlier Joint FAO/WHO Expert Committee on Food Additive (JECFA) report in 1995, had concluded that small amounts of nitrate/nitrite used as food additive is safe – the acceptable daily Intake (ADI) is 0-3.7mg/kg body weight per day for nitrate and 0-0.06 mg/kg body weight per day for nitrite (as expressed in ion form).
According to the report, of the 130 samples collected throughout this period, 69 were tested for nitrate and nitrite respectively. Three were found to exceed the permitted level of sodium nitrate, representing a non-compliance rate of 4.3%.
There were another 168 tests conducted on non-permitted preservatives, and all of them were proved satisfactory. Test results on the colouring matter were also reviewed in this report, and one of the 62 tested samples was detected with non-permitted colouring matter, resulting in 1.6% non-compliance rate.
So one may conclude that lap mei from Hong Kong are generally safe for consumption, and the application of nitrate/nitrite in curing is strictly controlled to the amount required to achieve the intended effect only, according to the report.
Spring festival and super bowl season
Two hot pots of lap mei farn