Underlying biochemical principle
Ginger-juice milk curd,locally called "Jiang Zhuang Nai," can be obtained by adding ginger juice to milk at an appropriate temperature and placing it in a static state at room temperature (Zhong and Chen,2017). Originating from Guangdong and Fujian Provinces in China,this dessert is cherished for its mellow taste,unique aroma,and health benefits. With advancements in food-processing techniques,there is a growing trend toward producing healthier foods using natural bioactive compounds (Castro-Muñoz et al.,2019),such as gingerol (Garza-Cadena et al.,2023),natural sweetener (Castro-Muñoz et al.,2022a),capsaicin (Castro-Muñoz et al.,2022b),anthocyanin (Hernández-Pinto et al.,2024),and carminic acid (Ferreyra-Suarez et al.,2024). Such foods are gaining popularity because of the increasing health consciousness of consumers and the perceived nutritional benefits and functional properties of such compounds. [4]
The most important part of the ginger in ginger milk curd is the ginger protease zingipain. This substance with molecular weight of 31 kDa is found with three forms of isoelectric point values around 5.58,5.40,and 5.22,respectively. The three forms have very similar biochemical behavior,where the optimal proteolytic activity is 40–60 °C (104–140 °F) and maximum clotting activity at 70 °C (158 °F). However,clotting decreases significantly at temperatures of 75 °C (167 °F) or above. [5]
Milk is a substance consisting mainly of milk fat globules and casein micelles in a continuous phase of water,sugar,whey protein and minerals. Casein micelles consist of mainly α(s1)-casein,α(s2)-casein,β-casein,and κ-casein,where hydrophobic αand β-casein are in the inner sub-micelle and hydrophilic κ-casein is in the outer part.
When the milk starts curdling,the curds are small,but as coagulation increases,curd size increases until the milk ends up with a tofu-like structure. [6] When the curdling occurs,the ginger protease cuts open the κ-casein so that the hydrophilic C-terminus and the hydrophobic N-terminus separate. This disrupts the stability of the casein micelle. In the hydrophobic effect,the hydrophobic casein coagulates. [7]
Health benefit
In addition to the volatile compounds of ginger juice and milk,ginger-juice milk curd has its own unique volatile compounds,such as decanoic acid,γ-elemene,and caryophyllene. Decanoic acid is a fatty acid that has a particularly unpleasant smell. It was produced when the curd was basically formed. If it can be eliminated or decreased,the quality of ginger-juice milk curd will improve. γ-Elemene contributed a pungent fragrance and is an effective anti-cancer ingredient. Caryophyllene has anti-inflammatory (Basha and Sankaranarayanan,2016) and antifungal properties. As a result,ginger-juice milk curd not only offers unique flavor characteristics but also potential health benefits,making it a valuable addition to the diet. [4]
Production method
Ingredients and Cooking Utensils (Serves one):
- 30 grams ginger
- 200 ml milk
- 2 tsp sugar
- thermometer
*About 165 kcal and 0.2 gram salt per portion
Cooking Steps:
1. Grate ginger,wrap in kitchen paper and squeeze out juice. There should be about 1 Tbsp juice but since water content of ginger determines the amount of juice,grate more ginger if juice is not enough.
2. Pour milk in small pot and mix in sugar. Place on low heat and warm while checking the temperature with a thermometer. To avoid diminishing the function of enzyme in ginger juice waiting to be mixed,turn off heat just before temperature reaches 70 degrees.
3. Add ginger juice in bowl and pour warmed milk at once. Temperature of milk will fall,nearing the temperature at which ginger's enzyme works best. Leave for 4 to 5 minutes. [8]
Cultural significance
Hand-brewed ginger milk curd is one of the important representatives of Lingnan desserts,fully embodying Lingnan people's life attitude and spirit of enjoying life,maintaining health,and working hard. Sorting out the history of the emergence and development of this traditional food,as well as its production techniques,has certain cultural value for the study of the catering culture and folk customs of the Lingnan region.
It is widely popular among locals. With the increasing international influence of Cantonese desserts,it has also gained recognition and affection from people in different regions. The market prospects are broad. At the same time,the popularity of this product can also drive the development of related agricultural industries,helping farmers get out of poverty and become prosperous. Therefore,this product has certain economic value and can directly stimulate the development of related primary,secondary,and tertiary industries. [9]
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