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principles concerning canning fruits nutritional canned 代寫

Laboratory Report-Pear Canning
1. Introduction
In order to fully understand the principles concerning the manufacture and quality control of canning fruits, the practice of making canned pears was done, and then a lab report was written. From the experiment we can arrive at a conclusion that canning of pears is not a very complicated process, however, there are exist many detailed issues which may affect the quality and nutrition of the fruits. There are some pivotal controls for manufacturing high quality safe canned fruit. For instance, you have to sort and grade fruit before canning in case there are bruised or misshaped ones. In addition, those naturally matured pears should also have pressures between 3 to 4 kg, and the target concentration of total dissolved solid should be 8.5-10.5 oB. After all the procedures, the PH of the canned pears should be 4.4 because high pH of the fruit may be unsafe and too low pH means the fruit is not ripe enough (Karel & Lund, 2003). What’s more the final Brix should be about 13 to 16. With all the specific details being considered and strictly-operated quality control, can only safe and nutritional canned pears being produced.
 
2.    Method
During the production of canned pears, there are mainly a few steps. Firstly, we should evaluate the quality of the raw fruit, in this case, pears. We collected 1 kg pears of uniformed size and shape. Of all the 1 kg pears, we tested the firmness of one chosen pear using penetrometer. There are two steps: slicing off small area of the pear skin is the premise. Then we could measure its pressure or firmness by carefully plunge penetrometer into the exposed flesh. The next step is to assess the brix of the fresh pears (Rahman, 2007). The brix was measured by refractometer. We also measured the pH of the pear. Furthermore, we also checked the syrup strength with refractometer. 
 
The second step involved in cleaning, peeling and pear slices. Normally the pears were cored and cut to halves and quarters. During this process, the pears would get oxidized and turned brown, so we used a solution containing ascorbic acid and citric acid to withstand browning (Ramaswamy, 2006).
 
Thirdly, the trimmed and diced pears were weighted about 220 to 240 g then packed into a standard 400g can and filled with preheated syrup. During the process, we aimed for 15 mm head space. And then we heated the open cans to 80 ℃ to remove air and blanch the fruit. Then we placed lids onto the can while at 80 ℃ and used boiling water heat treatment (100 ℃) for sterilization for at least 20 minutes.
 
Fourthly, the can was transferred into the cooling tank which is filled with chlorinated water. When the temperature was down to 38-40 ℃, we removed it to dry on trolley. After a further cooling procedure about 30 minutes, the canned pears can be final inspected.
 
Last but not the least, after we labelled the canned pear, we made a assessment of the canned pears. There are a few indicators we evaluated, including weight of the cans, equilibrium brix, and descriptive sensory assessment like colour, texture, sweetness level, flavour and acceptability.
 
3.    Results
Table1. Assessment of pear quality

Firmness testing pH Pear brix Syrup brix Pear wt Waste wt
2.6 3.5 12.6 21.8 819.8 185.2
 
Table2. The final brix of syrup canned pear
  Brix Weight Sugar Final brix
Pear 12.6 225.2 28.38  
Syrup 21.8 220.5 48.07  
    445.7 76.45 17.2
 
Table3. Assessment of canned pears
Final brix pH Bioyield point Flesh firmness
17.2 4.28 83.32 42.15
 
Figue1. Weight of the canned pears

Figue2. Sensory analysis of canned pears

 
4.    Discussion
From the introduction, we can know that the perfect brix of pear should fall into 8.5-10.5, and in fact, a high brix level means that the pear is very ripe with high sugar level. However, after evaluation, we found out the brix value of the chosen pear was 12.6. This may be part of the reasons why the final brix was 17.2 since the normal range of the target final brix should be in the range of 13-16 (Puig, 1996). So in order to achieve the target, in effect we have to adjust sugar syrup concentration lower. In the experiment, the brix of the syrup we have used is 21.8. According to the CODEX guidelines for packing media for canned fruits, it belonged to the heavy syrup. So maybe in the next calculation, we should choose some light syrup. Furthermore, concerning the final pH of the canned pears, our result is 4.28 and it was in the normal range, and obviously it was acidic enough to ensure it was preserved safely.
 
As far as the descriptive sensory analysis of canned pears is concerned, we have arrived at some conclusions comparing UWS pear with the commercial pears. Firstly, we believe that the commercial pears are much white than our UWS pear, this may concerned with our techniques dealing with the oxidation of vitamin C. Secondly, both of the two kinds of pears are very firm and the commercial one is firmer than UWS pear. Thirdly, as we have discussed above, since we the brix is higher of UWS pear, so when talking about the sweetness of pear and pear flavor, there were significant difference between the UWS pear and the commercial pears. And the UWS pear was sweeter and more tasteful. Finally, we concur that the there was a huge difference between UWS pear and commercial pears in relation to overall acceptability. And UWS pear was liked extremely. 
 
From the further calculation, we can know the drained weight of pears was 230.2 g, and the percent drained weight was 57.5%, which was within the CODEX specification 55-60% for canned fruit.  
 
5.    Conclusion
In sum, concerning the chemical and physical characteristics of the canned pears, we believe that the process of making canned pears was successful and strictly-controlled. Yet, though we followed the instructions in the learning guide thoroughly, there exist some minor errors and unstandardized operations during the practice which caused the deviation of the final results. So we must record the procedures concerning temperature and time carefully to manufacture safe and tasteful pears.
 
 
 
6. Reference
CODEX guidelines for packing media for canned fruits, No CAC/GL 51-2003
 
Karel, M & Lund, D B 2003, Physical principles of food preservation, Marcel Dekker, New York. NSW Food Authority
 
Puig, L, Varga, DM, Chen, P M & Mielke, EA 1996, ‘Synchronizing Ripening in Individual Bartlett' Pears with Ethylene’. HortTechnology, vol6, no.1, pp.24-27.
 
Rahman, M S 2007, Handbook of Food Preservation, 2th edn, CRC Press, Boca Raton.
 
Ramaswamy, HS. 2006. Thermal Processing of Fruits, 2th edn, CRC Press. Boca Raton.
 
 

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