Pickle unit: swollen jars after salt reduction
A small pickle unit in Howrah produces mango pickle in 20 kg food-grade plastic jars. To cut cost, the owner reduced salt from 12% to 8% (w/w) and added potassium metabisulphite at 0.05%, within the permitted level. The product pH is 3.8. Jars are filled warm, sealed, and stored in a room at 30–35 °C. After three weeks, 6 of 40 jars have swollen lids and a yeasty smell; the owner wants to open the jars, add more salt, re-seal them and sell them as 'fresh stock'. No date of packing or lot number is printed. The unit has no validated shelf-life data. A retailer has already paid for 10 jars and wants a replacement.
1. Explain, using water activity, pH, preservative and headspace, why the jars swelled. Is the product unsafe?
Read the worked answer
Salt lowers water activity by binding free water. Reducing salt from 12% to 8% leaves more free water available to spoilage yeasts and moulds. The pH of 3.8 is acidic, but acidity does not inhibit all yeasts and moulds, especially in a warm room. Potassium metabisulphite at 0.05% may be insufficient against a high initial microbial load, and its effectiveness depends on pH, temperature and headspace. Warm filling into sealed jars creates condensation and a humid headspace; if the fill temperature and seal are not controlled, surviving organisms can ferment and produce gas. Swollen lids plus a yeasty smell are strong evidence of microbial gas production. The product is spoiled and unsafe; it should not be sold. Re-salting and re-sealing would not make it safe because microbial metabolites and dead organisms remain.
2. What should you do about the 6 swollen jars, the remaining 34 jars and the retailer's 10 jars? Justify each action.
Read the worked answer
Segregate the 6 swollen jars and do not allow them to be opened, re-salted or re-labelled. Condemn and destroy them by an approved method, with a destruction record and witnesses. Hold the remaining 34 jars pending investigation; they are not automatically safe merely because they have not yet swollen. Sample them for yeast/mould and check salt, pH and preservative levels. Recall or replace the retailer's 10 jars and retrieve them where possible; the retailer should not sell them. The absence of date of packing and lot number is a labelling/traceability violation and prevents a targeted recall. Issue an improvement notice requiring process validation, shelf-life data and lot coding. The owner's proposal to sell reworked stock is not acceptable.
3. Propose three process controls, with reasons, that the unit should adopt before resuming production.
Read the worked answer
First, fix and validate the salt/water-activity target and the pH target; salt must not be reduced unless the resulting water activity is shown to control the intended spoilage flora. Second, control the preservative effectively: use the permitted level that is validated for the actual pH, microbial load and shelf life, and monitor its concentration rather than assuming 0.05% is enough. Third, control filling and sealing: use a validated hot-fill or pasteurisation step, check seal integrity, and cool/store within a specified temperature range. Supporting controls are hygienic raw-material handling, validated shelf-life studies, and date/lot coding for traceability. These controls address the free-water, acidity, preservative and headspace problems that caused the swelling.