ABSTRACT
Conjugated linoleic acid (CLA) is a polyunsaturated fatty acid with various positional and geometric isomers of linoleic acid (LA) present mainly in food items and produced endogenously in non-ruminants and humans or through fermentation process. It is associated with health-beneficial effects and subject to more research on its natural sources (ruminant-derived foods) and strategies to increase the content in various foodstuffs. Although several studies have reported the most common intake value of 0.8 g/day (0.6 to 3.0 g/day), research for raising in situ concentration should focus on strategies such as in vitro bioconversion of its precursors by bacteria and supplementation of LA rich-oils in foods fermentation process. In this study, the ability of some lactic acid bacteria (LAB) from diverse samples to produce CLA from sunflower oil and the effect on production yield of fermentation medium supplementation with carbonate calcium were investigated. Results showed that ten Limosilactobacillus fermentum and Enterococcus faecium produced trans-10, cis-12-CLA isomer accounted for at least 85% of total CLA ranging from 4.64 to 5.22 µg/mL. Despite the fermentation medium supplementation with CaCO3 enhanced the production yield, the residual LA inhibitory effect on bacteria growth governing CLA biosynthesis process was not mitigated. So, although our LAB strains can produce CLA, the more the LA concentration goes up, the more the conversion rate downgrades. Further studies on strains behavior in a wide range of LA concentrations will help establish a stable relationship between bacteria and LA in the presence of CaCO3.
ABSTRACT
Abstract Hydroxymethylfurfural (HMF) is a quality indicator, especially in foods where changes in protein-carbohydrate interactions are observed during the applied process. In this study absorbance and L*, a*, b* values of red color emerged due to the relationship between hydroxymethylfurfural (HMF) and resorcinol during the modified Seliwanoff test were used as input data artificial neural network (ANN) to determine the HMF concentration for the first time. A linear relationship, between HMF concentration and absorbance of red color, can be represented by equation absorbance = 0.0020 + 0.0012* concentration of HMF (mg L-1) with R2 = 99.6%, Fisher ratio: 0.18, p value of lack of fit: 0.975, correlation coefficient: 0.9960. Intra-day and inter-day precision expressed as relative standard deviation (RSD) %, were 2.35 - 3.65% and 3.16 - 4.73%, respectively. Recovery rates and RSDs were in the range of 99.34 - 100.47% and 1.58 - 3.68%. It showed high correlation compared to HPLC method used as reference method (0.998). The R2 values of ANN for estimation of HMF concentration were found 0.90 for training, 0.96 for validation, and 0.99 for testing and AARD was found 8.85%. Evaluation of the absorbance and L*, a*, b* values of the red color with artificial intelligence is a reliable way to determine the HMF concentration.