Tutorial for Topic 3 & 4 by Joey JY https://padlet.com/joey_eng_jy/360rmemhz46t A processor recently started producing a new vacuum-packaged, low-heat processed, low-fat meat product with an expected shelf life of 60 days at 4.4°C. He found that 10% of the product was getting spoiled within 30-40 days. The characteristics were an accumulation of gas and purge (cloudy), with acidic and cheesy odor. He asks you to help him determine the causes and resolve the problem. Explain briefly how you plan to proceed in order to understand the problem (causes, sources, etc.) and solve it. en-us 2018-10-10 03:23:10 UTC 2018-11-01 13:55:12 UTC hello@padlet.com Jonathan Bryan Lee 0316680 https://padlet.com/joey_eng_jy/360rmemhz46t/wish/293809787 Since the food is vacuum packaged, the microorganism causing the spoilage is definitely anaerobic. Meat contains mostly protein so the gas accumulation, purge and odour is caused by putrefacation of the meat proteins into amino acids, ammonia and hydrogen sulfide. I suspect the microbe suspected of this spoilage must be of the Clostridium genus. In order to truly identify and pinpoint the spoilage microorganism as Clostridium, certain selective media must be used to try and isolate Clostridium colonies from the food sample. If Clostridium is successfully isolated as the spoilage organism, steps must be taken to inhibit its growth.

The source of the contamination may be due to improper handling of the meat such as exposure to soil. Moreover, the low-heat processing may not be enough to kill all the Clostridia in the food before packaging. The low-heat could possibly shock the Clostridia enough to produce spores but not enough to kill them and the spores.

One step that can be taken is using better thermal processing such as a higher temperature for a shorter time so that the organoleptic properties of the product are minimally affected. Another step that can be taken is adding nitrate or nitrite to the meat product as it inhibits Clostridial spore germination and toxin production. Adding antimicrobial bacteriocins such as Nisin to the food can inhibit growth of anaerobic microbes during food storage. Subjecting the product to a pulsed electric field or ultrasound can also help in lowering the initial microbial load.]]> 2018-10-17 12:54:03 UTC https://padlet.com/joey_eng_jy/360rmemhz46t/wish/293809787 Isaac Aoki 0332816,Giselle Ho 0333421, Carina Effendi 0331250, Teoh Wen Xin 0333301, Lim Ke Wen0329129 https://padlet.com/joey_eng_jy/360rmemhz46t/wish/294357475 Causes: 
  • It might be cause by mesophilic pathogens, (e.g., Yersinia enterocolitica and Listeria monocytogenes) and spoilage bacteria (e.g., Leuconostoc spp., several Lactobacillus spp., and Serratia spp.), that can grow in vacuum- and modified-air (MA) packaged foods at 0 to 1 degree celcius. Spoilage of vacuum packaged meats by the psychrophilic Clostridium spp. with a growth range between –2 and 20 degree celcius was also reported.
  • Vacuum- or MA-packaged refrigerated (lower than 5 degree celcius) foods are expected to inhibit the growth of aerobic, most mesophilic, and thermophilic microorganisms. However, if the product contains dissolved or trapped oxygen and the modified air contains oxygen, aerobic and microaerophilic microorganisms capable of growing at refrigerated temperatures can also grow as long as the oxygen is available. Similar possibilities also exist if the packaging material is relatively permeable to atmospheric oxygen.
  • Even under ideal conditions (no oxygen and refrigeration at lower of equals to 5 degree celcius), the vacuum-packaged unheated foods normally harbor both anaerobic and facultative anaerobic spoilage and pathogenic bacteria that can multiply during refrigerated storage.
  • Heat-processed products are usually given a low-heat treatment that, depending on a product, varies from 60 to 74 degree celcius for a specified time. At this temperature, pathogenic and spoilage bacterial spores and cells of some thermoduric bacteria can survive. Some of these survivors can be anaerobic and facultative anaerobic and can multiply at refrigerated temperatures. 
  • It is most likely caused by the leuconostocs (one species of lactic acid bacteria) contaminated the products as postheat contaminants from the equipment and other sources during handling before vacuum packaging.
  • The acidic and cheesy bacteria could be caused by the growth of lactic acid bacteria


Resolve:
  • To prevent the remain in oxygen in the vacuum-packaged meat, a non toxic oxygen absorber should be in the package to completely remove any minute oxygen molecules in the packaging. If vacuum packaging is permeable to oxygen, the chances of bacteria growth increases tremendously. The material used to package meat should not be permeable to oxygen. 
  • The meat preservation method should be freezing instead of refrigeration to extend shelf life and also to prevent bacteria growth. 
  • Equipment handling meat should be cleaned and undergo a UV treatment to eradicate most bacteria habitating in the machines. 
]]> 2018-10-18 14:10:08 UTC https://padlet.com/joey_eng_jy/360rmemhz46t/wish/294357475 Nicholas Gan Yu Xing 0327633 https://padlet.com/joey_eng_jy/360rmemhz46t/wish/295999519 Provided that the object of contamination was in an environment lacking of oxygen, the culprit of the contamination was narrowed down to be anaerobic in nature. The absence of oxygen within environment of contamination negates the possibility of aerobic bacteria being found in the contaminated object. Based on the temperature which is 4.4°C, bacteria that can possibly grow under anaerobic condition and cold temperatures are Yersinia enterocolitica, Listeria monocytogenes, Clostridium botulinum and Lactobacillus strains.
The acidic and cheesy odor may be derived from lactic acid bacteria such as Lactobacillus strains. Improper handling of food during the packaging or preparation period may have introduced some facultative anaerobic bacteria which may have caused the spoilage.

The equipment used to prepare the food should be thoroughly sterilized. Freezing would be recommended as the bacterial growth will be inhibited and the meat will be able to last longer.

]]> 2018-10-23 15:07:07 UTC https://padlet.com/joey_eng_jy/360rmemhz46t/wish/295999519 0324802 Lim Jia Xin https://padlet.com/joey_eng_jy/360rmemhz46t/wish/299359458 Lactic acid bacteria and clostridium. 

Causes- low heat processing and the storage of temperature. Improper handling of the food and contamination of the raw ingredients.

Resolve - Apply low heat longer time at 90°C for 10 minutes and find out the D-value required to kill 90% of the microbes population to ensure the food is heated at sufficient time and temperature to be considered as safe. Add salt or sugar as a preservatives to reduce the water activity. Add nitrate to preserve the colour of the product and inhibit the growth of clostridium. Store the food at proper temperature in the freezer where clostridium and other bacteria cannot grow which is below 8°C. The packaging should not have high permeability to oxygen which will cause oxidation and allow aerobic microbes to grow. Nisin which is a bacteriocin can be added to prevent clostridium. After vacuum packaging, allow pasteurisation to take place and then speed cooling and distribute at appropriate temperature. 



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