Degradation Kinetics of Anthocyanins from Purple Eggplant in a Fortified Food Model System during Microwave and Frying Treatments

A model food system was designed with dietary fiber and crude anthocyanins from purple eggplant peel to explore the degradation mechanism of anthocyanins during microwave and frying treatments. Our results found that delphinidin-3-O-rutinoside was either hydrolyzed into delphinidin or condensed with p-coumaric acid to form p-coumaroyl-delphinidin-3-O-glucoside. Delphinidin was cleaved into gallic acid and phloroglucinaldehyde, which might be further oxidized into pyrogallol and phloroglucinol, respectively. The total anthocyanin degradation followed the first-order kinetics in fried and microwaved solid matrix samples as well as microwaved liquid matrix samples. However, the total anthocyanin degradation followed the second-order kinetics in the heated liquid matrix samples at the frying temperature. The brown/polymeric color index, which negatively correlated with the anthocyanin content, increased faster in the liquid matrix samples than in the solid matrix samples. Compared with frying treatment, a higher rate of anthocyanin degradation in solution was observed under microwave treatment. However, anthocyanins were subject to much more damage under frying treatment than microwave treatment in a solid food system.

GC-MS Analysis, Antioxidant and Antimicrobial Activities of Achillea Odorata Subsp. Pectinata and Ruta Montana Essential Oils and Their Potential Use as Food Preservatives

In order to discover new natural resources with biological properties, the chemical composition, the antioxidant and antimicrobial activities, and the potential use as food preservative of essential oils of Moroccan Achillea odorata subsp. pectinata (AO_pEO) and Ruta montana (RMEO) were studied. Gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of 21 and 25 compounds in AO_pEO and RMEO, respectively. The results showed that the major compounds of AO_pEO are camphor (45.01%), bornyl acetate (15.07%), borneol (11.33%), β-eudesmol (4.74%), camphene (3.58%), and 1.8-cineole (eucalyptol) (2.96%), whereas 2-undecanone (63.97%), camphor (3.82%) and cyclopropanecarboxylic acid (3.66%) were the main components of RMEO. The antioxidant activities were evaluated by diphenylpicrylhydraziyl radical (DPPH) and reducing power assays. The antimicrobial activities of essential oils were tested against bacterial strains and food contaminant yeast using agar disc diffusion and microdilution methods. A significant antimicrobial activity of AO_pEO was observed against Bacillus subtilis, Proteus mirabilis and Candida albicans, compared to RMEO. The efficacy of AO_pEO was also evaluated in model food systems (cabbage and barley) artificially inoculated during storage. The results found that the adding of a minimal inhibitory concentration (MIC) and 4× MIC were potent in decreasing the Proteus mirabilis growth in food model systems. Our findings suggested that AO_pEO may be potentially used as an alternative food preservative.

Inhibition of Listeria monocytogenes , Escherichia coli O157:H7, and Micrococcus luteus by Linear Furanocoumarins in a Model Food System

Lime peel, parsnip, lemon peel, dried parsley flakes, cold pressed lime oil, and distilled lime oil samples were analyzed for the presence and concentration of the linear furanocoumarins (LFs) psoralen, 5-methoxypsoralen (5- MOP), and 8-methoxypsoralen (8-MOP) by thin layer chromatography and gas chromatography mass spectrometry. Cold-pressed lime oil had the highest LF content (psoralen, 67 ± 29 μg/ml, 5-MOP, 1,634 ± 62 μg/ml, and 8-MOP, 44 ± 2 μg/ml). The antimicrobial effectiveness of LFs against Listeria monocytogenes , Escherichia coli O157:H7, and Micrococcus luteus was tested in a model food system consisting of a slurry of 25% commercial "garden vegetables" baby food in 0.1% peptone water. Inhibition required UV activation after the addition of the LFs to the model system. Lime peel extract, cold-pressed lime oil, and a 5-MOP standard inhibited the growth of L. monocytogenes , but not E. coli O157:H7. M. luteus was inhibited only by the cold-pressed lime oil. The minimum LF concentration that caused inhibition of the growth of L. monocytogenes was 32 μg/g and the minimum bactericidal concentration was 43 μg/g. Cold-pressed lime oil inhibited L. monocytogenes even at the lowest concentration added to the model system (10 μg/g), while the corresponding LF standard did not. This suggested the presence of other antimicrobial agents in the oil.