Romanee Sanguandeekul

Autochthonous yeasts associated with mature pineapple fruits, freshly crushed juice and their ferments; and the chemical changes during natural fermentation

This study investigated autochthonous yeasts and their functions in the spontaneous fermentation of freshly crushed pineapple juice samples collected from two different areas of both Thailand and Australia. Hanseniaspora uvarum and Pichia guilliermondii were the main yeast species observed on the fruit skins of Thai samples, and also in the fresh juice and ferments of all samples from both countries. P. guilliermondii was consistently present as the dominant species during the early stage of the fermentation, whereas H. uvarum became more prevalent towards the end of the six-day fermentation period, with populations increasing from an initial level of approximately 5 log CFU/mL to approximately 8 log CFU/mL at the end of fermentation. The ethanol levels in samples from both regions of Thailand were maximal at 2 days of fermentation, reaching approximately 1 to 2% (v/v) but then declined thereafter. In contrast, in the Australian samples ethanol levels continued to increase over the entire six-day fermentation period and reached approximately 3 to 4% (v/v). A significant decrease in citric acid and increase in lactic acid levels were observed throughout the fermentation period in the samples from Thailand, but not in those from Australia where the different acid contents (and pH) were relatively stable. The other wine yeasts and, in particular, Saccharomyces yeasts, were not found in any of sampled fermentation systems that is apparently different from the other fruit juices. These findings suggested that the freshly crushed pineapple juice may possibly have some effects on the other autochthonous yeasts having important role in alcoholic fermentation.

Effect of Plasticizer Type and Concentration on the Properties of Edible Film from Water-Soluble Fish Proteins in Surimi Wash-Water

Edible film made from water-soluble fish proteins present in surimi wash-water were developed based on formulation conditions explored in a previous study. Type and concentration of plasticizer significantly (p < 0.05) affected the mechanical and barrier properties of the films. Sorbitol (SOR) plasticized films were the most brittle, with the highest tensile strength (TS, 3.14MPa) however its effect on water vapour permeability (WVP) was low (30.41g/mm/m2/d/kPa). In contrast, glycerol (GLY) and polyethylene glycol (PEG) plasticized films exhibited flexible structure despite a low TS (2.13MPa and 1.80MPa, respectively) resulting in higher WVP (125.8g/mm/m2/d/kPa and 89.52g/mm/m2/d/kPa). As plasticizer concentration increased, TS decreased concomitant with an increase in elongation as break (E) and higher WVP. SOR plasticized films, showed higher film solubility (FS) and protein solubility (PS) compared to GLY and PEG plasticized films. Increasing the plasticizer concentration, overall, resulted in both higher FS and PS. The colour of films was more affected by the nature of the plasticizer used than by its concentration.

Optimization of cinnamon oil nanoemulsions using phase inversion temperature method: Impact of oil phase composition and surfactant concentration

Essential oils, such as those isolated from cinnamon, are effective natural antimicrobial agents, but their utilization is limited by their low water-solubility. In this study, phase inversion temperature (PIT) was used to prepare cinnamon oil nanoemulsions. To this aim, it was hypothesized that cinnamon oil nanoemulsions could be fabricated by optimizing the oil phase composition and surfactant concentration of the system and their stability could be enhanced using a cooling-dilution method during the PIT. A mixture of cinnamon oil, non-ionic surfactant, and water was heated above the PIT of the system, and then rapidly cooled with continuous stirring, which led to the spontaneous generation of small oil droplets. The impact of oil phase composition and surfactant concentration on the formation and stability of the nanoemulsions was determined. Cinnamon oil nanoemulsions with the smallest mean droplet diameter (101 nm) were formed using 40:60 wt% of cinnamon oil and medium chain triglyceride (MCT) in the total lipid phase. Increasing surfactant concentration significantly decreased the mean droplet diameter of the nanoemulsions but did not alter their particle morphology. In addition, using the cooling-dilution method, the nanoemulsions were stable for at least 31 days when stored at 4 °C or 25 °C.