Thank you so much for your response. I have also considered that four factors. But I have justifications for each of them. So, I arrived at the conclusion that the problem was due to temp abuse upon delivery. I need your insights on these:
1. Under-pasteurized: We pasteur our products by batch but bloating occurs only to 1 to 2 out of 100 to 150 packs which made it a very isolated case. We have also checked the heat distribution on the products and it passed our standard.
2. Chiller temperature: Yes, it is monitored and recorded 4 times a day.
3. Warehouse temp of customer: We really haven't checked our customer's storage. But every time we reply to their complaints regarding temperature abuse, they always say that they have the right temperature.
4. Micro-leaking: I have also considered this but I don't have any way to verify that this is the cause. How do you verify yours?
Thank you so much for your help. What is ROP by the way?
1. Granting that you HD is good, do you conduct heat penetration test to know your heat treatment process schedule could give you the desired P-value/F-value to give your product its target shelf-life provided it is stored and distributed in normal condition?
2. if you monitor your storage 4 times a day, which IMO, the interval is long, ours is hourly, do you install a continuous temperature chart recorder? If you dont, chances are recording might not be done in real time. Though temperature rises, operator still record the required temp to avoid questioning. It is the reality. Specially in night time when bosses are not around operators have their monitoring log book filled up at the end the shift. Please check.
3. Try to include visit on your distributor facility as part of your complaint handling. This situation might be similar in number 2.
4. Possible is micro leak. Do you conduct heat sealing strength of you packaging before production, WIP and right after the shift? It might your sealing is not complete or during pasteurization it loosen. Heat seal strength normally reduced by 20% after heat treatment process. Checking micro leak of our packaging with product, is putting the product in a basin of potable water. Bubbles come out if there is leak in your packaging on the sealing or on the body itself.
During transport what was the highest temperature and the longest your product is exposed? How shortly (time of exposure) is short?
IMO, the reason that only 2 out of 150 is involved, it might that two have micro leak/pinholes, received less heat treatment, and were abused. The fermentation that cause bloating takes 15-17 days
in their warehouse to take. It all depends on the bacterial that survive after pasteurization or the introduction of bacteria through packaging leak and the storage condition that your customer has.