Antioxidative effects of stabilized and unstabilized defatted rice bran methanolic extracts on the stability of rice bran oil under accelerated conditions

Evaluation of process involved in the production of aromatic compounds in Gram-negative bacteria isolated from vanilla (Vanilla planifolia ex. Andrews) beans

AIM

The present investigation was aimed at isolating and identifying bacterial strains from cured vanilla beans. Additionally, the study focused on evaluating bacterial processes pertaining to the aromatic compounds production (ACP).

METHODS AND RESULTS

Three bacteria were isolated from Vanilla planifolia beans, previously subjected to the curing process. According to morphological, biochemical and 16S rRNA analysis, the strains were identified as Citrobacter sp., Enterobacter sp. and Pseudomonas sp. The polygalacturonase activity (PGA) was determined using the drop, cup-plate and DNS methods. Aromatic compounds production was analysed by cup-plate method using FA as substrate and quantified by high performance liquid chromatography (ppm), the functional groups of vanillic acid (VA) were identified by FT-IR and the aromatic compounds (AC) resistance was determined and reported as minimum inhibitory concentration. Citrobacter sp., Enterobacter sp. and Pseudomonas showed PGA (70·31 ± 364, 76·07 ± 12·47 and 51 ± 10·92 U ml^-1 respectively), were producers of VA (3·23 ± 0·49, 324 ± 41 and 265·99 ± 11·61 ppm respectively) and were resistant to AC.

CONCLUSIONS

The Gram-negative bacteria isolated from V. planifolia beans were responsible for ACP.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first evidence for the role of Gram-negative bacterial isolates from cured Mexican V. planifolia beans in the process related to ACP.

Synthesis and Surface Properties of Anionic Vinylguaiacol Based Surfactants

By changing amino acid head group four biobased anionic surfactants were synthesized using 4-vinylguaiacol and methylbromo undecanoate. The synthesized surfactants were characterized by NMR and mass spectrometry analysis. The surface active properties such as surface tension, wetting power, foaming characteristic, emulsion stability, calcium tolerance were studied and compared with those of sodium lauryl sulfate (SLS). Excellent emulsion stabilities and calcium tolerances were observed for the synthesized surfactants. These surfactants show a lower critical micelle concentration as compared to the conventional surfactants. The bulk micellization properties were studied using dynamic light scattering and fluorescence anisotropy technique. The antimicrobial and cytotoxicity studies were also carried out.

Changes in Physicochemical, Structural, and Sensory Properties of Irradiated Brown Japonica Rice during Storage

Brown japonica rice was treated with (60)Co γ irradiation at doses of 0, 0.2, 0.5, 1.0, and 2.0 kGy immediately after harvesting. The effects of irradiation on physicochemical, structural, and sensory properties during long-term storage (18 months) were investigated. The study revealed that the pasting properties, including peak, through, breakdown, final, and setback viscosities, decrease considerably in a dose-dependent manner and vary differently during 18 months of storage. Irradiation reduced the free fatty acid (FFA) content in comparison with unirradiated brown rice with long-term storage (from 12 to 18 months). Scanning electron microscope (SEM) observation showed that the mean range and shape of starch granules did not vary significantly. However, dark spots developed among starch granules and the narrow cracks became wider with increasing irradiation dose and storage time. During sensory evaluation, extremely low scores for odor and overall acceptability were obtained for medium-dose irradiated rice (1.0 and 2.0 kGy); however, no significant difference was found in acceptability between low-dose irradiated rice (0.2 and 0.5 kGy) and the control rice (0 kGy). Overall, low-dose (0.5 kGy or below) irradiation seems to be a promising alternative treatment to increase brown rice shelf life, without affecting the physicochemical and structural characteristics and sensory acceptability.