Testo puts measurement at centre of frying control

Testo is positioning objective frying-oil measurement as a more repeatable alternative to fixed replacement schedules and visual inspection, using total polar materials alongside temperature and digital records to help operators manage oil condition through its working life.

The company’s testo 270 BT measures total polar materials, or TPM, directly in hot oil and displays the result as a percentage. Measurements can be transferred through Bluetooth to the testo Smart App, where operators can document readings, review trends, and export records for quality-control purposes.

The basic argument is that appearance alone gives an incomplete picture of oil condition. Frying oil changes continually as it is exposed to heat, oxygen, moisture released from food, crumbs, coatings, salt, and repeated heating and cooling cycles. Different products can also darken oil at different rates, meaning colour and smell do not necessarily track the level of chemical degradation closely enough to provide a consistent replacement rule.

TPM provides a measurable parameter instead. Polar compounds accumulate as triglycerides break down during frying, and their proportion increases as the oil is subjected to further thermal and chemical stress. Measuring that change gives operators a way to compare oil condition between fryers, shifts, and operating days rather than relying on individual judgement.

Replacing oil on condition rather than schedule

Testo’s own guidance places frying oil below 20% TPM in its green range, between 20% and 24% in orange, and above 24% in red. It identifies 14% to 20% TPM as an optimum frying range, while allowing users to configure different upper and lower thresholds according to their own process and operating requirements.

Those values should not be confused with a universal legal limit. Regulatory approaches differ by country, while oil type, product, process, and quality systems can also affect the limits a business chooses to apply. The useful industrial principle is therefore the ability to measure against a defined internal or regulatory threshold rather than treating one supplier’s traffic-light setting as a substitute for local compliance requirements.

Completely fresh oil is not always the point at which fried food develops its most familiar colour and surface characteristics. As oil is used, changes in its physical and chemical properties influence heat transfer, browning, flavour development, and the interaction between the food surface and the frying medium. The problem begins when useful ageing moves into excessive degradation.

Temperature remains inseparable from that process. Frying too cool can extend cook time and alter oil uptake and texture, while excessive heat accelerates degradation. Operators therefore have to control both the thermal process and the condition of the oil rather than assuming that one correct fryer set point will produce consistent results throughout an entire oil cycle.

Actual oil temperature can also move significantly during production. Loading frozen or chilled food removes heat, and a fryer with insufficient recovery capacity can operate below its nominal set point for a meaningful part of the cooking cycle. Conversely, poorly controlled equipment or light loading can leave oil exposed to unnecessarily high temperature between batches.

Oil-management routines consequently extend beyond replacement. Filtration removes crumbs and residues that can continue to degrade in the fryer, while topping up introduces fresh oil and changes the overall TPM level. Cleaning practice, fryer loading, idle periods, product composition, and the type of oil selected all influence how quickly the frying medium reaches the business’s intervention threshold.

The testo 270 BT is designed to make one part of that routine more reproducible. Testo instructs users to remove fried food and residues, wait until bubbling associated with water has subsided, immerse the probe to the specified depth, and allow the reading to stabilise. The instrument reports both TPM and temperature, with colour-coded feedback and optional app-supported measurement.

Its stated TPM measuring range is 0% to 40%, with a typical accuracy of ±2 percentage points between 40°C and 190°C under Testo’s reference conditions. The instrument can be used with or without the app, while measurement records can be exported as CSV files or PDF reports.

That documentation becomes more useful as the number of fryers, operators, and sites increases. An experienced cook may develop a reliable sense of how a particular fryer behaves, but a multi-site catering business or high-volume food operation needs a method that can be repeated by staff with different levels of experience.

Trend data can also point towards process problems. If one fryer consistently reaches the replacement threshold faster than equivalent equipment, managers can investigate temperature control, filtration, product residues, cleaning, loading practice, or the products being cooked rather than simply accepting higher oil use at that station.

The economics provide the second part of Testo’s case. Replacing oil while it remains usable increases raw-material cost and waste, while keeping it beyond the chosen condition limit can undermine flavour, colour, texture, and consistency. Testo says regular measurement with the 270 BT can reduce frying-oil use by up to 20%, although the saving available to an individual business will depend on its starting practices, throughput, oil costs, and product mix.

That percentage should therefore be treated as a supplier claim rather than a guaranteed saving. A site already using tightly controlled oil-management procedures may have less waste to remove than a business replacing every fryer on a fixed timetable regardless of condition.

The stronger operational argument is consistency. Measuring TPM gives quality teams a defined parameter that can sit alongside fryer-temperature checks, filtration schedules, cleaning records, and corrective actions. It also provides a clearer basis for explaining why oil was retained, filtered, topped up, or discarded on a particular shift.

French fries illustrate the issue because customers expect a narrow quality window: a crisp exterior, an evenly developed colour, a soft centre, and no stale or excessively oily character. Similar controls apply to fried poultry, fish, dough products, and industrial snack production, even though their operating conditions differ.

Frying-oil condition is therefore better treated as a process variable than a consumable that simply expires after a fixed number of hours. Temperature is measured rather than guessed elsewhere in food production, and refrigeration records are routinely logged against defined limits. TPM measurement applies the same logic to an input whose condition changes every time the fryer is used.