Knafa Bjoz

The science of knafeh

Why the cheese stretches, why it is soaked first, why cooks use ghee, what browns the pastry, and what lemon does to the syrup.

By Knafa Bjoz editorsPublished

Also known as: kunafa science, why knafeh cheese stretches

Good knafeh depends on a few pieces of kitchen chemistry: a cheese that melts and stretches, fat that browns the pastry without burning, and a syrup that stays smooth.

Why the cheese stretches

Cheese is held together by a network of milk proteins called casein, bound up with calcium. In stretchy cheeses, how much calcium is attached to the casein decides how the cheese behaves: as that calcium falls, the protein network holds more water and becomes more pliable.[1] Cheese with a lot of calcium overall melts less well.[1]

For knafeh this matters. Food scientists in Jordan, testing Nabulsi cheese, write that it “should show meltability and high stretchability” to make high-quality kunafa.[2] In their trials, lowering the cheese’s pH slightly gave a low but acceptable level of melt and stretch,[2] and another team found that an enzyme added to the brine gave Nabulsi an “outstanding fibrous structure”.[3]

Why the cheese is soaked first

Nabulsi cheese is stored in brine with more than 18% salt for up to a year. In one study the cheese itself was close to 10% salt.[4] That is far too salty for a sweet, so cooks soak it in water overnight before use.[4] Soaking also changes the texture: in the same study, removing the salt made the cheese much softer.[4]

Why ghee

Ghee, or samneh, is butter with the water and milk solids removed.[5] Under the international food standard, ghee is at least 99.6% milk fat.[6] Without the milk solids, which burn first, it can be heated far hotter than butter before it smokes; McGill University’s Office for Science and Society gives about 250 °C for clarified butter against about 150 °C for butter.[5] That lets the pastry crisp and colour without a burnt taste.

What browns the pastry

The golden crust comes largely from the Maillard reaction, in which sugars react with proteins and amino acids as food heats, creating new flavours and colour.[7]

The syrup

Knafeh syrup is sugar boiled with water, often with a little lemon juice. In Antakya the registered recipe calls for about 60% sugar to 40% water, with a few drops of lemon.[10] The lemon is not only for flavour: acid splits some of the sugar into glucose and fructose, which get in the way of sugar crystals forming, so the syrup stays smooth.[8]

Many cooks follow a rule of temperature contrast: cold syrup over hot pastry. Claudia Roden’s konafa recipe, for example, pours the cold syrup over the hot pastry “as it comes out of the oven”.[9] We have not yet found a tested scientific explanation for why this keeps the pastry crisp, so we treat it as a cooks’ rule, not a proven one.

Kitchen science quiz

  1. Why can ghee get hotter than butter without burning?
    Show answer

    Answer: Its water and milk solids have been removed. Ghee is butter without the water and milk solids, which are what burn first. Read more

  2. What does a little lemon juice do in the syrup?
    Show answer

    Answer: Helps stop sugar crystals forming. Acid splits some sugar into glucose and fructose, which get in the way of crystals forming. Read more

  3. The golden crust comes largely from which reaction?
    Show answer

    Answer: The Maillard reaction. Sugars react with proteins and amino acids as food heats, creating flavour and colour. Read more

  4. Cold syrup on hot pastry: what do we know?
    Show answer

    Answer: It's a cooks' rule without a tested scientific explanation yet. Many cooks follow the rule, but we haven't found a tested explanation, so we treat it as a cooks' rule. Read more

Sources

  1. 1.Gonçalves M.C. and Cardarelli H.R.. Mozzarella Cheese Stretching: A Minireview. Food Technology and Biotechnology, 2021, vol. 59, no. 1, pp. 82–91.
  2. 2.Mazahreh A.S., Quasem J.M., Al-Shawabkeh A.F. and Afaneh I.A.. The Effect of adjusting pH on Stretchability and Meltability to White Brined Nabulsi Cheese. American Journal of Applied Sciences, 2009, vol. 6, no. 4, pp. 543–550.
  3. 3.Abu-Alruz K. et al.. Effect of Proteases on Meltability and Stretchability of Nabulsi Cheese. American Journal of Agricultural and Biological Sciences, 2009, vol. 4, no. 3, pp. 173–178.
  4. 4.Khaled Abu-Alruz. Quality of White-Brined Nabulsi Cheese Made with Different Proportions of Sheep's and Cows' Milk. Current Research in Nutrition and Food Science Journal, 2023, vol. 11, no. 1.
  5. 5.Ada McVean. Is Ghee Healthier Than Normal Butter?. McGill University Office for Science and Society, 2018.
  6. 6.Anhydrous Milk Fat (AMF) and Butter Oil. Tetra Pak Dairy Processing Handbook, chapter 15, table 15.1.
  7. 7.Liu S. et al.. Insights into flavor and key influencing factors of Maillard reaction products: A recent update. Frontiers in Nutrition, 2022.
  8. 8.Preventing Sugar Crystals in Simple Syrup. America's Test Kitchen.
  9. 9.Darina Allen: Claudia Roden's Konafa with a Cream Filling. Irish Examiner, 2016.
  10. 10.Antakya Künefesi, geographical indication registration no. 101. Turkish Patent and Trademark Office (TÜRKPATENT), 2008.