Processing Methods and Technical Key Points for Almond Milk
Almond, also known as badam or American sweet almond, is a dried-fruit tree mainly grown for its kernels. Its kernels are rich in nutrients, sweet, and pleasantly fragrant; they can be eaten raw and also processed into many kinds of foods. The processing techniques for almond kernels are as follows.
1. Process flow
Material selection -> soaking -> peeling -> color protection -> grinding -> filtration -> blending -> homogenization -> deaeration -> bottling -> sealing -> sterilization -> cooling -> finished product
2. Processing techniques
1. Material selection: choose almond kernels that are fresh in color, plump, milky white in flesh, dry, and free from deterioration.
2. Soaking: put the almond kernels into a washing tank, rinse them clean with running clear water, then place them in 2-3 times their volume of water and soak for 12 hours to soften.
3. Peeling: one of the following methods may be used for peeling.
(1) Manual method. Remove the seed coat by hand from fully soaked almond kernels.
(2) Peeling-agent method. In a heatable container, add 100 kg of water, 0.5 kg-1 kg of food-grade sodium hydroxide, and 0.1%-0.2% of a dehydrating agent to make a peeling solution, heat it and keep it at no lower than 90°C. Soak a bamboo basket containing almond kernels in the peeling solution for 2-5 minutes, then lift it out and immediately rinse with tap water, shaking the basket to help the seed coats fall off.
(3) Mechanical method. The almond peeler consists of two wooden cylindrical rollers 22 cm in diameter and 60 cm long, driven by gears to rotate in opposite directions at different speeds. The almond kernels are rubbed between the two rollers, removing the seed coats.
4. Color protection: place the peeled almond kernels in a color-protecting solution composed of 0.2% sodium bisulfite and 0.3% citric acid and soak for 15 minutes to protect color and neutralize residual alkali.
5. Grinding: rinse the color-protected almond kernels 2-3 times with tap water, then add 15 times the weight of the almonds in water and grind into a slurry. The screen aperture of the grinder is about 0.8 mm.
6. Filtration: when the temperature of the almond slurry drops to 40-50°C, carry out hot filtration. First roughly filter with a 120-mesh screen, then finely filter with a 190-mesh screen.
7. Blending: add 5%-10% white granulated sugar, citric acid, and stabilizer to adjust the product composition and state. To avoid reduced protein solubility and coagulation, the pH of the almond milk should be adjusted to 6.8, and the acid should be added with rapid stirring to avoid excessive local acidity, which can cause layering and precipitation.
8. Homogenization: use a colloid mill (Zhengzhou Yuxiang Food Machinery Co., Ltd., postal code: 450003, address: North Section of Nanyang Road, Zhengzhou City, Henan Province, telephone: 0371-66675962, 013103833308) to homogenize 3 times at 70-75°C and 20-30 MPa, in order to crush and refine protein particles and fat globules and appropriately increase the viscosity of the emulsion to ensure product stability. If homogenizing only once, control the homogenization pressure at 38 MPa.
9. Deaeration: heat the homogenized emulsion in a hot-and-cold tank to 90% to remove part of the gas in the emulsion and prevent contamination before canning.
10. Canning and capping: control the emulsion temperature at about 70°C and fill it into 250 mL glass bottles.
11. Sterilization and cooling: send the filled bottles into a sterilization retort for sterilization; the sterilization formula is: 10'-30'-10'/100°C. Cool successively with water at 50-60°C and 30-40°C.
12. Heat preservation and inspection: send the product into a heat-preservation warehouse at 37±2°C and keep it for 5-7 days; remove nonconforming products and then store them in the warehouse.