Effect of Storage Conditions on 2–Acetyl-1–pyrroline Content in Aromatic Rice Variety, Khao Dawk Mali 105

ABSTRACT: The effect of package and temperature on 2–acetyl-1–pyrroline content in milled aromatic rice during storage was investigated. 2 -Acetyl-1 -pyrroline content was decreased faster at higher storage temperature. However, fat acidity of rice was increased during storage and inversely correlated with 2–acetyl-1–pyrroline content at an early stage of storage. The difference in 2–acetyl-1 -pyrroline recovery from the samples, which were extracted with ethanol at 40 °C and 75 °C, revealed that the starch bound and free forms of 2–acetyl-1–pyrroline may occur in aromatic rice. These results suggested that the biosynthesis of 2–acetyl-1 -pyrroline before starch structure formation in rice kernel could play a key role in the aroma quality of aromatic rice.     

Emulsion stabilization mechanism of combination of esterified maltodextrin and Tween 80 in oil-in-water emulsions

Food Science and Biotechnology - Esterified maltodextrins (EMs) were prepared using enzyme-catalyzed reaction of maltodextrin (DE of 16 and 9) and palmitic acid. The emulsion stabilization...     

Investigation of undeclared food allergens in commercial Thai food products

This study investigates the presence of undeclared allergens - namely milk, egg, wheat and peanut - in commercial processed food products in Thailand. Out of 142 commercial products, 55 positive cases were found (by quantitative ELISA method) to contain an undeclared allergen greater than 10 ppm. Among all positive products, undeclared milk appeared the most frequently (21 cases), followed by egg and wheat with similar frequency (17 cases), while peanut was rarely found. Milk- or egg-positive products were further confirmed by the presence of the milk protein, casein, or the egg protein, ovalbumin, by Western blot test. Our results should help to increase the awareness among Thai food manufacturers of the need for more careful management of allergenic food ingredients, and to encourage the labeling of allergen information for allergic consumers, thus reducing the health hazard from food allergy.     

Study of hybrid dryer prototype and its application in pregerminated rough rice drying

In this study, a hybrid dyer, combining heat pump drying (HPD) with fluidized bed drying (FBD) concepts were designed and fabricated. The pregerminated rough rice (pre-GRR) was dried in multistage using this hybrid dryer to compare with the single-stage drying by hot air dryer. The objectives were to test the application of this hybrid dryer and determine the suitable drying condition for pre-GRR. The result indicated that the punched plate distributor was the most suitable distributor. The pre-GRR should be dried by the three-stage drying method using either FBD or HPD at 45°C in the last stage to obtain higher head rice yield, lower fissure grain, and better color values than their counterparts. The scanning electron micrographs proved that starch gelatinization occurred when applying FBD at temperatures between 100 and 140°C causing the adhesive connections inside the kernels and subsequent decrease in fissures.     

Development and characterization of a prototype of a lactic acid–based time–temperature indicator for monitoring food product quality

Temperature is a crucial factor affecting the quality and safety of food products during both distribution and storage. The difficulty in controlling and monitoring the temperature history of food products makes it difficult to precisely predict shelf life. Time–temperature indicators (TTIs) provide a visual summary of a product’s accumulated chill-chain history, recording the effects of both time and temperature. Attempts have been made to develop a prototype of a time–temperature indicator based on the diffusion of lactic acid, which is temperature-dependent. Four lactic acid-based TTIs were made in different substrate concentrations. Color changes associated with the diffusion of lactic acid were monitored. In the vapor diffusion of lactic acid, an irreversible color change of a chemical chromatic indicator (from green to red) clearly and progressively occurred due to the pH reduction. The temperature dependence of these TTIs kinetics was characterized isothermally in the range of 4–45 °C, yielding activation energy (E_a) of, approximately, 50 kJ mol⁻¹. The mathematical models of each TTI were established according to the relationships between color changes and time and temperature. The differences between the E_a values of the TTIs and the E_a associated with food quality losses – including enzymatic loss, hydrolysis, lipid oxidation, nutrient loss and microbial growth – were less than 40 kJ mol⁻¹, and therefore these TTIs could be considered as good candidates to monitor food quality losses. Although these TTIs do not cover the whole range of food quality losses, they could be applied to show the time–temperature history of some foods, especially fruits and vegetables, and to indicate food quality associated with time–temperature exposure.