Joshua Downs¹, Marnie Brennan¹, Vincenzo Di Bari², Agnieszka Zoltowska¹, Thomas Hackney¹, Christopher Ford³, David Gardner¹

¹University of Nottingham, School of Veterinary Medicine and Science, Nottingham, United Kingdom. ²University of Nottingham, Food, Nutrition and Dietetics, Nottingham, United Kingdom. ³Adelaide University, School of Agriculture, Food & Wine, Adelaide, Australia

Objectives

To determine the tartaric acid content of fresh grape and dried grape (raisin/sultana/currant) samples, as a predictor for canine grape toxicity. To explore if cooking raisins within baked goods reduces tartaric acid content.

Methods

Representative samples of fresh grapes, dried grapes, and raisins in baked goods were homogenised in orthophosphoric acid and tartaric acid measured by high performance liquid chromatography. Grape varieties were referenced based on their size, colour, seeded vs unseeded, and sourcing (commercial e.g. supermarket vs non-commercial e.g. private residence).

Results

Tartaric acid content of fresh grapes ranged from 4.54-8.08 grams per kg of fresh weight (5.95 +/- [0.89] g/kg). Dried grapes had approximately five times greater tartaric acid content (28.84 +/- [3.05] g/kg). Non-commercial and seeded grapes appeared to have different tartaric acid content relative to commercial and unseeded grapes. Raisins within baked goods cooked at high temperatures (200°C) recorded similar tartaric acid content as un-cooked raisins.

Statement: Impact/ Clinical Significance

Tartaric acid content in samples appeared to vary across some of the factors investigated. Knowledge of these factors at diagnosis could facilitate better decision making. The lack of tartaric acid breakdown in baked goods suggests thermal decomposition is unlikely to cause the reduced toxicity seen in these cases. Expanding the findings from this pilot study to include assessment of grape characteristics from confirmed cases of grape toxicity may provide stronger evidence for potential risk factors.