Why?

Monday, April 13, 2015



If you have been following my blog, you will know that I have done a few posts on Sio Bak, Siew Yoke or Cantonese Roast Pork.

I have even claimed that I have perfected the techniques.

Not quite.

  • There has been times when the skin won't crisped. This is especially so when I have pricked the skin, using some forks. 
  • There has been times when I decided not to prick the skin. The skin was crisped, but only partially. The inner skin can be chewy.
I have always wondered: why do you need to prick the skin? Maybe I have missed something in googling cooking sites but I have never found the answer.

So, when someone who worked in a popular Cantonese restaurant chain explained to me why recently, I was all ears. As I have said before, I am a keen learner.

He said that the skin need to be pricked to ensure that the skin is crisped throughout, from the top to the bottom. This way, the skin won't "chi ngah" (he was speaking Cantonese, what else?) i.e. parts of it won't be stuck to your teeth. You need to prick the skin lightly so that heat can reach the bottom layer of the skin. This way, when you bite through it is a crispy crunch all the way through the skin.

But you must not prick through the skin into the fat layer below it, or else, the liquid from the fats will flood the skins, making it difficult to crisp.  

It was an important piece of the puzzle and as I look back, I now understand why some batches did not turn out right.

And using any sharp instrument won't do. And so, I finally bought myself this nail thingy. I am not sure what to call it. It only cost $3.

I hope you find this tip helpful.

If you are using the Sous Vide method, the skin will be cooked and it is easy to prick it before you oven it. If you are using the conventional all-oven method, blanch the skin first before you prick. Or, you can prick it half way through the roasting.

Have fun, *crunch* and enjoy. Sio Bak is indeed one of our culinary wonders.




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19 comments

  1. i don't quite comprehend the meaning of "But you must not prick through the skin,..." could you elaborate?

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  2. ah ha! I had been wondering why my past few attempts did not result in a crisp skin despite my skin pricking with the naily thingamajig. So perhaps the skin was pricked too hard and the nail entered the fat as you described! Will consider a less heavy hand and more deft in my next siew yoke attempt. Thanks for sharing!

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  3. Edmund - prick the skin but do not go all e way and hit the underlying fat.

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  4. Tks. Always thought I needed to poke thru in the same way scoring helps let the oils out. Come to think of it, clogs happen even with scoring.

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  5. This comment has been removed by the author.

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  6. Then again. How do the Spanish lechon achieve the crispness without scoring or pricking? More research to do...

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  7. Interesting Ed, about the spanish lechon. I could be wrong, but for baby pigs, like chinese suckling pigs, their skins are not thick, thus less a need for scoring or poking. Maybe....not very sure myself. But I am sure the normal pork I use for sio Bak needs some poking as some parts do "stick to the teeth"

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  8. thanks for the info like some of you i have tried a number of times to cook roast pork and sometimes part of the skin does not crisp and turns out to be chewy.I have tried drying out the pork in the fridge before roasting but it still the same so much so that everytime it stresses me out!! You mention blanching the meat first before scouring the skin how long does one blanch it for and what temperature should we roast it at? Thanks

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  9. and here's my "elementary-ish scientific" reason. The Skin is made up of Collagen, keratin, gelatin etc....in a very dense extracellular Matrix. During broiling, or even deep frying, those pockets of air space created by the needles when heated up will expand very very rapidly, causing "blistering" which produces a far superior crunch deep into the Collagen and gelatin layer in the Skin. Poking through the Skin will only create "channels/tunnels" from the underlying fat/muscle (which has lotsa moisture. These channels will allow the "Juices" to run from the fat/muscle up to the Skin during the heating process which effectively "cools down and moistens" the opened "vents" preventing the Expansion of the air pockets. Effectively, this will not cause the Skin to crackle.

    The western style of using oil to fry up the Skin only works the surface that is in contact with the oil, not within. Hence, sometimes we get the nice outer crunch but bl**dy tough / chewy Center of western style pork crackling.

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  10. Hi, thanks for the information! I have been thinking of making my own sio bak. Where did you buy the pricking tool, your nail thingy? Thanks!

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  11. Sorry to hijack (temporarily), but @ James, technically, you dont Need to purchase that pricking tool. I myself dont own such a tool, but i got some sturdy (translates to large Diameter) needles (sewing needles are fine as Long as they are not so fragile), tied them up together or insert them through a rubber stopper such that they Exit the other side and there u have, a pork Skin prickling tool!

    :-)

    hope this helps

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  12. The aggregate on the net seems to suggest prepping of the skin is in order to maximize crunch probability. Goes along the line of denaturing the skin cellular networks via use of acid, akaline, alcohol or heat. I use baking powder myself which gives it 100% results everytime, but skin ends up really puffy. Just wondering if there is any technique that would result in pig crackling akin to a roast suckling pig or roast duck.

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  13. ed, enzymatic or chemical methods of denaturation of skin cellular structure is different from creating literally "embolism" within the Skin itself :-D. Maybe the pigs here (in Germany) have a thicker skin!!!!!! thats y ive to murder the pork belly with multiple stab wounds! LOL
    Alcohol generally dehydrates the surface too. By using baking powder, the pH of the Skin surface is also increased. This is akin to more "alkali" surface which is easier to Speed up the Mallaird reaction, hence easier to get the "browning" and since is also a dehydrating agent, will result in the surface of the Skin to become really puffy when broiled.
    not sure about roast suckling pig but definitely havent found a "modernized" way close enough to the papery crunch of good roast ducks. (I'M MISSING THIS AND AM HUNGRY ALREADY!!!!!!)

    Heston Blumenthal tried using all sorta techniques to try to get the same quality, but in the end concedes that there are some techniques that modern methods do not replicate sufficiently and faithfully.

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  14. Catherine - if blanching, a quick 5 minutes should suffice. As for oven temperatures, I use 180-200 C to crackle the skin. I have not worked out the temp for cooking as I prefer to use the Sous Vide method. If oven all the way, google for it as there are various ways of doing it.

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  15. On top of pricking, I should add that the Cantonese Sio Bak method of charring the skin black and then scraping it off and crackle again is one way of thinning the skin and create a papery crunch, akin to roast duck.

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  16. Where can I buy the nail thingy in Singapore?

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  17. Pricking of the belly pork skin before scalding and then stewing as kong bak pao also helps to turn the fats gelatinous. I don't know how but I found that by not pricking the skin, the fats can become chewy regardless how long you stew the dish.

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  18. I'm late but I remembered your puzzling over the pricking of the skin. I just came across this website with a possible explanation. Raymond of http://www.theartofcooking.org/chinese-recipes/crispy-roasted-pork-belly-siu-yuk/ explained it this way:
    If you look closely at the skin (epidermis), the skin should be puffy and airy, it should expand during the cooking process. The expansion of the skin is what make the skin crunchy and crispy but not hard. So what makes the skin expands during the cooking process? The answer is Baking Soda and vinegar. The Baking Soda along with a little bit of water seeps down into the punctured skin thus soften or loosen the connective tissue of the epidermis and the dermis. After the skin soften, the introduction of vinegar reacts with Baking Soda which produces CO2, the CO2 will expand the epidermis and dermis. ......After that comes the drying process, the drying process is what makes the skin crackly and crunchy. To get that crackly and crunchy texture, the skin must be air dry (dry overnight in the fridge or use a fan to dry it) until there is no moisture present.

    I am certain there are a number of ways to get that crispy skin but which way is the most desirable? The vodka/alcohol method seems most promising. https://forums.egullet.org/topic/108508-siu-yook-roast-pork-belly/?page=2#comment-1531721

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