# Evaluation of an Electronic Nose Coupled with In Vitro Fecal Fermentation as a Screening Tool for Fecal Odor in Cats

## TL;DR

Researchers tested an electronic nose with in vitro fecal fermentation to quickly screen supplements that reduce cat fecal odor.

## Contribution

The study demonstrates that an electronic nose can effectively screen fecal odor modulation in cats, offering a faster and more practical alternative to traditional methods.

## Key findings

- The eNose system successfully differentiated odor profile changes caused by dietary supplements.
- Fructooligosaccharides and oat beta-glucans showed stronger odor-modulating effects than Yucca and Quillaja extracts.
- The eNose performed comparably to GC-MS in detecting fecal odor differences.

## Abstract

Evaluating the effectiveness of dietary fecal deodorizing supplements in cats is time-consuming and costly when conventional analytical methods are used. Previous studies have relied on in vitro fecal inoculation combined with gas chromatography–mass spectrometry, but data interpretation is complex and limits its use as a rapid screening tool. Electronic nose (eNose) technology offers a faster and more practical alternative. This study evaluated an in vitro fecal inoculation system coupled with an eNose as a rapid screening method for dietary fecal odor modulation in cats. Using this approach, four commonly used supplements—Yucca schidigera extract, Quillaja saponaria extract, fructooligosaccharides, and oat beta-glucans—were assessed. The method effectively differentiated odor profile changes induced by dietary supplements. Among the tested ingredients, Quillaja saponaria extract showed the weakest odor-modulating effect. Yucca schidigera extract produced minor alterations in odor characteristics, whereas fructooligosaccharides and oat beta-glucans demonstrated greater odor-modulating effects relative to the control. These findings support the use of an eNose-based in vitro system as a practical screening tool for fecal deodorant efficacy in feline nutrition research.

In vitro fecal inoculation coupled with gas chromatography–mass spectrometry (GC-MS) has been used for evaluating fecal deodorants. However, high cost and complex data interpretation limit its routine application. An electronic nose (eNose) offers a rapid, cost-effective alternative. This study aimed to evaluate the eNose as a screening tool for fecal odor compared with solid-phase microextraction gas chromatography–mass spectrometry (SPME GC-MS) and to examine the in vitro effects of fecal deodorant supplements on fecal odor profiles. Feces from ten healthy cats were serially diluted (1:1 to 1:8) and analyzed using both instruments. Four dietary supplements—Yucca schidigera extract (YSE), Quillaja saponaria extract (QSE), fructooligosaccharides (FOS), and oat beta-glucans (OBG)—were tested at concentrations of 0.0, 0.2, 0.4, and 0.8 g/100 mL. The eNose showed comparable performance to GC-MS in discriminating among sample dilutions. In vitro fermentation showed that FOS and OBG significantly increased volatile fatty acid (VFA)-related sensor responses while signals linked to ammonia and sulfur compounds were reduced. QSE had minimal effect, whereas YSE produced moderate changes. The total sensor response intensities did not differ between treatments. These findings indicate that prebiotic supplements exert stronger effects than saponin-based supplements and highlight the potential of eNoses with in vitro fermentation for rapid screening of fecal deodorants.