CHAPTER 3. RESULTS AND DISCUSSIONS 3.1. DETERMINATION OF THE QUALITY OF RAW SEA GRAPES
3.2. STUDY ON PRE-PROCESSING RAW SEA GRAPES
The purpose of washing is to remove most microorganisms and some impurities on the surface of the sea grapes, and to minimize the risk of damage.
The research shows that the appropriate amount of water to wash is 15 liters/kg sea grapes; washing time: 8 minutes/ times and number of washing times: 3 times. With these good washing conditions, the microbiological criteria and the quality meet standards.
3.2.2. The stage for re-planting raw materials
When being harvested, the vertical stems of sea grapes are cut from the horizontal roots. The re-planting period helps sea grapes heal the cuts, grow roots and live normally, increase the resistance of sea grapes, prolong the preservation time.
The study shows that the suitable conditions for re-planting sea grapes are the rate of sea grapes in the culture medium: 2%; the culture time: 2 days; the dissolved oxygen in water: 8 mg/l; the light intensity from 10-15klux, the temperature of culture
medium is 280C. The sea grapes grown in the above conditions can heal with the rate of 95.7%, green intensity is 43.7%, the total aerobic bacteria remains on the sea grapes is 323 cfu/g and the sensory quality of fresh sea grapes is good.
3.2.3. Centrifuging to separate water on the surface of sea grapes
At the end of the re-planting stage, the water content on the sea grapes is quite high. If they are immediately packaged and stored, they will be quickly spoiled.
Therefore, centrifuging is necessary.
The research results show that the percentage of water removed from the surface of fresh sea grapes corresponding to a centrifuge speed 300 rpm in 30 seconds is 10%.
After being extracted water, sea grapes have enough conditions for preservation.
3.2.4. Design of quipments used for the preliminary processing before preservation at the pilot scale, the yield of 100 kg of material / batch
The thesis studies the design, produces the circulatory equipment for preliminary processing, the recovery growing of sea grapes is at the pilot scale, the yield is 100kg of material/batch. The equipment works on the principles: the static tank working with the dynamic process carried out by the circulation of circulating water and aeration. The rectangular equipment is made of the stainless steel of 304, size of 6000mm x 1080mm, the curved bottom. The equipment has full range of sensors which can adjust the temperature in the range of +20 ÷ + 300C, the salt concentration in the range of 0 - 10%, the concentration of dissolved oxygen in the range 0-20mg/litter. Sea grapes planted within 2 days in this equipment has the recovery rate of more than 80%, even they can recover completely and meet the quality standards of fresh food according to the current regulations of Vietnam.
Figure 3.1. The principles of preliminary processing system Notes:
MN:air compressor DN: Outdoor unit air conditioner cooling (Gree)
RV: Bottom exhaust valve
F2: water filter Drying filter P: Pump
HS: Heat resistance DL: The hose device with the horizontal cover.
BTL: Throttle
* The operation principles of the system:
- The cooling system will cool, control and mantain the temperature of sea water at a temperature of 280C ± 20C. At the cooler, the vertical twist hose is insulated with PU (poly urethane). At this device, a heat resistance is installed in case the environmental temperature is below 28°C, the cooler system will stop and the resistance is supplied the electricity to produce heat and make sea water hot before entering the tank for pre-processing.
- Sea water after being cleaned is pumped through the cooling system to maintain the proper temperature for the pre-processing of sea grapes (28 2)°C, and then it is pumped into the pre-processing tank. In the preliminary tank, the aeration system will provide the gas in order to dissolve the oxygen in water and helps sea grapes, water circulate from the bottom to the top. As a result, sea grapes at the bottom will be moved upward and expose to light to increase the photosynthesis, they can recover their
"health". This process makes the dirt on the sea grapes be removed, which helps sea grapes clean. When the dirt is removed from the sea grapes, water will be dirty, then the
Parts for handling seagrapes Parts for seawater cooling
Water supply Pneumatic
Tank 1 Tank 2 Tank 6
Overcover parts
user will turn on the water recirculation pump system to pump dirty sea water out of the tank, and refill the filtered water back to the tank. Thus, sea water in the tank is always circulated in the tank and it is sometimes pumped out of the tank when it is dirty.
Thus, during operation, the temperature of the sea water in the tank, the dissolved oxygen content, the salt concentration of water in the tank and the illumination intensity of the lighting system are controlled to ensure the proper conditions for photosynthesis, growth and recovery of sea grapes.
Figure 3.2. The equipment fot recovery of sea grapes, the yield of 300kg material/batch
Figure 3.3. Sea grapes are damaged
after harvest
Figure 3.4. Sea grapes have a recovery after being pre-processed