Kjedahl; NIR; food testing; food quality; food analytics

Chapter 37

Ready, set, go! Kjeldahl vs NIR in the race for most efficient food analytics

🏫 Workshop overview: The team clearly needs a break from their case load and Shallot Holmes comes up with a great workshop just in time to save the mood in the office. See two food detectives hold a great scientific debate over the merits of Kjeldahl vs NIR in the food testing lab. Who comes out on top? See if you agree.

Shallot Holmes walks into the office and gets immediately hit by the foul mood of his colleagues. They all seem to have gotten up from the wrong side of the bed this morning and are sitting around in silence, exchanging grumpy looks every few minutes.

Two in particular, Miss Mapple and Eggcule Poirot are in such a stinky, rotten mood, Shallot Holmes catches himself wondering if they have not hung out with some shady apples and eggs well beyond their expiration date the day before. But he knows just the remedy for this type of grumpiness. A real battle of the wits! He recalls the success of Lieutenant Cornlumbo and Nancy Beef battling it out over NIR vs IR spectroscopy and quickly devises a similar plan.

He calls in Miss Mapple and Eggcule Poirot and presents his workshop idea to the two food detectives. They visibly brighten up, quickly prepare themselves and then call in the rest of their team members. Shallot Holmes announces that the battle over Kjeldahl vs NIR is about to begin. The others sit back, their bad mood already starting to evaporate.

Miss Mapple explains that they would like to compare two techniques often used in food analytics, Kjeldahl as a reference method and NIR as a technology capable of delivering real-time data.

Eggcule Poirot kindly takes over and explains that in their discussion, they will consider best fit based on application range, sample type variation, possibility to automate throughput, how fast the method is, unattended operation capabilities, compliance, start-up investment, and finally, how environmentally friendly the method is.

The two detectives get started on:

Kjeldahl vs NIR: application scope

Eggcule Poirot’s eggy chest puffs out with more and more pride as he lists the impressive list of parameters you can measure with NIR: fat, protein, moisture, ash, starch, lactose and more! The food detective summarizes that you can measure a broad range of sample properties easily and simultaneously. But he is not yet finished. He adds that you can also use a NIR system to perform qualitative analysis to test product quality, conformity or flag adulteration.

Miss Mapple shoots him a defeated, but still cheeky look. She proudly states that Kjeldahl is the gold standard reference method for protein determination. She adds steam distillation can also be used to measure volatiles such as vicinal diketones, alcohol, essential oils and non-protein nitrogen, but she admits that the NIR is the superior method in terms of application versatility.

Kjeldahl vs NIR: sample variability

Eggcule Poirot grabs the first word again and starts to explain that NIR calibrations are easily updated whenever small sample changes occur. But Miss Mapple is quick to jump in and point out that if the samples or sample formulations are ever-changing, constantly tweaking the NIR calibrations becomes impractical. Instead, she highlights that acid digestion and steam distillation can be easily applied to various nitrogen-containing products for accurate protein analysis, even as formulations are under development. The food detectives are unanimous, Kjeldahl is the better choice for samples that are constantly changing.

Kjeldahl vs NIR: Automaton and high throughput

Which system can process more samples per workday, Kjeldahl or NIR? The team agrees only a concrete quantification can convince them. Miss Mapple gets to present first. She explains that even though Kjeldahl is a slower technique than NIR, a Kjeldahl digestion system can digest up to 20 samples at once. After digestion, 20 samples can be distilled and titrated in a Kjeldahl system. If the user operates the systems continuously, 120 samples can be processed by Kjeldahl in a 9-hour period.

Now it’s time for Eggcule Poirot to spit out some numbers. He tells the team that an at-line, or benchtop, NIR system involves measurement of one sample at a time with manual sample changes in-between multiple samples. The measurements, however, are very fast and take less than 1 minute. All in all, at least 200 samples can be measured for all calibrated proteins in 9 hours.

The team thinks the numbers are quite close, but Eggcule Poirot delivers the final nail in Kjeldahl’s coffin. He points out that if you use an on-line NIR system, you have a continuous stream of real-time measurement data with no manual work at all. Hence, NIR emerges as the better system for work that requires automation and high throughput capabilities.

Kjeldahl vs NIR: High sampling frequency

Miss Mapple argues that this section is linked to their previous argument, and she is bound to lose since Kjeldahl is slower than NIR in measuring each sample. But Eggcule Poirot refuses to miss a chance to brag about NIR technology.

He points out that at-line NIR instruments are simple to operate and can provide hygienic analysis directly in the control room or plant floor. The NIR systems can collect data for solids, liquid, powders, gels and pastes and measure multiple properties simultaneously with results in under 1 minute. And again, he emphasizes, an even faster option exists if you use an in-line or on-line NIR system. If the NIR instrument is integrated into hoppers, conveyer belts, mixers or other processing equipment, the operator can achieve real-time data and process control capabilities.

With NIR in hand, users can increase sampling frequency, which is important for optimal quality in food and beverage production, as well as for feed and forage ingredients, pre-mix, intermediates, and final products.

Kjeldahl vs NIR: Unattended operation

Miss Mapple sees a chance to get ahead. She points out that with the use of a Kjeldahl autosampler with certain Kjeldahl systems, unattended operation is possible during sample digestion and distillation and digestion. NIR, she is quick to add, requires manual sample changing.

But Eggcule Poirot refuses to be outdone. He argues that with NIR-Online ,unattended operation is possible without any manual work involved at all.

The team calls it a tie. Both Kjeldahl and NIR technologies offer decent options for hands-off work.

Kjeldahl vs NIR: Compliance

Miss Mapple giggles excitedly. Here she really sees her chance to shine. She explains that Kjeldahl is the most established reference method for protein determination in food, beverage, feed and forage. It is compliant with multiple national and international regulations, such as AOAC, ISO, DIN, LFGB and others. She shoots Eggcule Poirot a triumphant glance and gloats that Kjeldahl is often used as the primary reference method for NIR calibrations.

Eggcule Poirot smiles as he offers no objections. There are a few standards and norms about NIR in food and feed, but clearly, Kjeldahl wins the category of compliance.

Kjeldahl vs NIR: Initial costs

Miss Mapple is quick to start again. She explains that Kjeldahl products are often designed flexibly to meet a variety of budgets. Eggcule Poirot argues that NIR systems and NIR calibrations for various food and feed products are also often available at affordable start-up costs. Even more, once the NIR method is operational, the running costs are lower than with the Kjeldahl method and no consumables are required for routine sampling. The team concludes that even though NIR has lower running costs, Kjeldahl still requires a smaller start-up investment compared to NIR solutions.

Kjeldahl vs NIR: Sustainability

Miss Mapple tries to get a point in her favor. She insists that eco-friendly Kjeldahl consumables are available. But Eggcule Poirot swiftly shuts her down. NIR technology produces no emissions, requires no solvents or catalysis and operators do not come in contact with any chemicals when using NIR. Without much debate, NIR is the greener method.

The team applauds enthusiastically, and Shallot Holmes summarizes their exciting scientific debate on Kjeldahl vs NIR. Both technologies are clear winners, Kjeldahl for enabling compliance, unattended operation, and automation, and NIR for enabling multitasking and speed. No wonder, many food analysts prefer to have both in their arsenal. Ah, the bad mood in the office? What bad mood, everyone is as fresh as freshly squeezed orange juice. But luckily, not so sour.