Off-flavour in fried besan sev: oil abuse or packing failure?
A small namkeen unit in Jodhpur fries 12 kg of besan sev in a 40 kg batch of refined soybean oil and reuses the same oil for six consecutive batches over three days. Between shifts the oil sits in an open, unjacketed iron kadhai; it is never filtered, and make-up oil is added only when the level visibly drops. The sev is drained, cooled in the open room, and packed in 200 g HDPE pouches with roughly 15% headspace. The unit's godown has a west-facing tin roof and reaches 42 °C in May. After 18–20 days, wholesalers report a 'paint-like, oily' off-flavour in the May lots, although March lots were accepted. A lab report on a returned sample gives peroxide value 16.8 meq O2/kg, free fatty acids 0.9% as oleic acid, and moisture 4.6% in the sev. The owner wants to know whether the oil, the packing or the godown is at fault, and what must change before the next season.
1. Using the three reported figures, decide whether the returned sev is fit for sale and explain what each figure tells you about where the failure occurred.
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Verdict: not fit for sale. For refined edible oil the usual limits are FFA not more than about 0.25% (as oleic) and peroxide value not more than 10 meq O2/kg; the sample is roughly 3.6 times over on FFA and 1.7 times over on PV, and a fried snack should in any case be well below the oil limits because the oil is concentrated on the product surface.
Reading each number:
- FFA 0.9% is a hydrolysis signal: water (from the besan, from the open kadhai, from 4.6% product moisture) splitting triglycerides. Repeated heating accelerates it. So the frying oil was already degraded before packing.
- PV 16.8 meq/kg is an oxidation signal: hydroperoxides from oxygen attack, which then break down to aldehydes and ketones - the 'paint-like' note. This is what consumers actually taste.
- Moisture 4.6% in a fried sev is high (good practice is about 2–3%); it softens texture, feeds hydrolysis and lowers the barrier to oxidation.
Diagnosis: the primary fault is oil management (six cycles, no filtration, open to air and light), and the secondary fault is packaging/storage - HDPE is a poor oxygen and moisture barrier, 15% headspace leaves a large oxygen reservoir, and a 42 °C godown roughly doubles the rate of every oxidative reaction. March lots survived because ambient temperatures were lower.
2. Give the specific oil-management, cooling, packing and storage changes you would require, with numbers, and explain why each one works.
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Frying oil
- Cap oil at 3–4 fry cycles, or better on a measurable discard rule: retire the batch when FFA > 0.5%, PV > 10 meq/kg or total polar materials > 24–27%.
- Filter through a plate/filter-press (or at minimum a 100-mesh strainer plus filter aid) at the end of each shift to remove burnt fines, which catalyse further breakdown.
- Hold fry temperature at 160–175 °C; above about 180 °C polymerisation and acrolein formation rise sharply.
- Blanket or cover the kadhai, keep it out of direct light, and top up with fresh oil on a scheduled basis rather than only when the level drops.
Product
- Cool to below 35–40 °C before packing; hot packing drives moisture migration and oxidation.
- Target sev moisture of 2–3% by controlling dough water and fry time.
Packaging
- Move to a metallised polyester/PE or foil laminate with an OTR low enough to hold oxygen below about 2% for the intended shelf life; nitrogen-flush and reduce headspace to the minimum the filling machine allows.
- HDPE is acceptable only for a short, cool-chain life.
Storage
- Godown below 30 °C with reflective roof coating or insulation, pallets off the floor, FIFO with 30-day maximum age at dispatch.
Antioxidants are a supplement, not a substitute: a permitted antioxidant such as TBHQ within the maximum permitted level (about 200 mg/kg in the oil) slows oxidation but does nothing for hydrolysis, over-heating or a hot godown.
3. The owner proposes adding 0.02% BHA to the oil as the only change. Evaluate this proposal.
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It will not solve the problem, and on its own it is the wrong lever.
What BHA can do: it is a permitted phenolic antioxidant that scavenges free radicals and would slow the oxidation chain that produces the peroxide value and the paint-like aldehydes. At 0.02% (200 mg/kg) it is at the permitted level, so the dose is not the issue.
Why it is insufficient here:
- The oil is being held for six cycles at frying temperature. Antioxidants are consumed and are largely destroyed or steam-distilled at 170–180 °C, so most of the added dose is gone before the oil ever reaches the product.
- It does nothing about hydrolysis - the FFA will keep climbing because the water and the fryer fines are still there.
- It does nothing about the 42 °C godown or the HDPE/15% headspace, which is where most of the 18–20 day damage happens. An antioxidant only slows a reaction; it does not replace an oxygen barrier.
- Regulatory discipline: the additive must be a permitted antioxidant at permitted level for that food category, and its use does not excuse a product that fails on FFA and PV.
Better framing: treat BHA or TBHQ as the last 10% of the fix. Priority order is oil turnover and filtration, then cooling and moisture control, then an oxygen-barrier pack with nitrogen, then cool storage, and only then an antioxidant. Also note the additive must be declared on the label.