203: Impact of Pressure-Cooking and Fermentation With Lactobacillus Bulgaricus (LB6) on Ochratoxin A Reduction and Polyphenol Content of Grape Pomace

Introduction

Grape pomace (GP) is a polyphenol- and dietary fiber-rich byproduct of grapes from winemaking and has great potential to serve as a food and feed ingredient to improve human and animal health. However, limited studies have found that GP is often contaminated with high levels of Ochratoxin A (OTA), which has been reported to cause nephrotoxicity and renal tumors and other diseases in a variety of animal species. In this study, we examined the impacts of pressure-cooking at different pH and fermentation with L. bulgaricus (LB6) on OTA and different classes of polyphenols in the GP.

Methods

The GP obtained from a local winery was deseeded and adjusted to different pH with NaHCO₃, spiked to OTA concentration of 50ng/g GP, and then pressure cooked for 15-60 min. The untreated GP served as control. The fermentation was carried out anaerobically with L. brevis (LB6) at 42°C for 24-144 hours. The OTA and polyphenols were extracted with methanol and the OTA concentrations in extracts were determined using Ultra-Performance Liquid Chromatography (UPLC). The total anthocyanin (TA), total flavonoids (TF), and total polyphenols (TP) in extracts were quantified spectrophotometrically. Data were analyzed using a post-hoc Tukey's test and regression analysis.

Results

Pressure-cooking of GP without pH adjustment decreased the OTA content by 18-36% (P<0.05), while TF and TP concentrations increased quadratically (R²=0.9642-0.9145, p < 0.05) and TA concentration decreased exponentially with increasing treatment times (R²=0.995). In the pH range 5-7, pressure-cooking achieved 40-63% of OTA reductions (p < 0.05). Increasing pH of GP significantly enhanced OTA reduction by pressure-cooking. The extractable TF and TP contents were also increased, but TA decreased more significantly with increasing pH. Fermentation with LB6 only resulted in 31-51.6% OTA reduction.

Significance

Pressure-cooking of the GP at neutral pH can significantly reduce OTA content thus improving safety of OTA contaminated GP for livestock animals and human beings.

Authors: Ebenezer Aning-Sei, Jianmei Yu