This study was designed to determine the effect of osmotic dehydration (OD) process temperature (35-55 °C), sucrose concentration (40-60% w/w) and immersion time (90-210 min) on the water loss (WL), solid gain (SG), DPPH radical scavenging activity, ferric reducing antioxidant power (FRAP) and sensory quality of the dehydrated Terung Asam slices. Response Surface Methodology with Central Composite Design was applied to investigate the influence of these variables on the aforementioned responses. The increase in the levels of these processing parameters increased the WL and SG. The antioxidant activities also increased with sugar concentration, but reduced with immersion time and temperature elevation. About 36-80% of IC50 and 47-72% of FRAP were depleted after osmotic process. The loss of antioxidants was predominantly due to leaching during osmotic treatment rather than hot air drying. Despite the losses of these compounds, osmotic pretreatment was able to improve the sensory quality of the product. The optimum OD process condition was predicted as process temperature 38.1 °C, sucrose concentration 55.6% and osmotic duration 126.3 min.
The 3-Monochloropropane-1, 2-diol ester (3-MCPDE) and glycidyl ester (GE) are formed at high processing temperatures with the presence of respective precursors. Both are potentially harmful to humans, causing adverse health impacts including kidney damage, reproductive problems, and increased risk of cancer. The presence of 3-MCPDE and GE in palm oil is of particular concern because of its widespread use by the food industry. There are a variety of methods for reducing 3-MCPDE and GE. For example, water washing eliminates mostly inorganic chlorides that, in turn, reduce the formation of 3-MCPDE. 3-MCPDE has also been reduced by up to 99% using combinations of methods and replacing stripping steam with alcohol-based media. Activated carbon, clay, antioxidants, potassium-based salts, and other post-refining steps have positively lowered GE, ranging from 10 to 99%. Several approaches have been successful in reducing these process contaminants without affecting other quality metrics.
The rising concern about the presence of 3-monochloropropane 1,2 diol ester (3-MCPDE) and glycidyl ester (GE) in food has prompted much research to be conducted. Some process modifications and the use of specific chemicals have been employed to mitigate both 3-MCPDE and GE. Alkalisation using NaOH, KOH, alkali metals or alkaline earth metals and post sparging with steam or ethanol and short path distillation have shown simultaneous mitigation of 51-91% in 3-MCPDE and of 13-99% in GE, both contaminants achieved below 1000 µg/kg. Some of the mitigation methods have resulted in undesirable deterioration in other parameters of the refined oil. When the processed oil is used in food processing, it results in changes to 3-MCPDE and GE. Repeated deep frying above 170 °C in the presence of NaCl and baking at 200 °C with flavouring (dried garlic and onion), resulted in increased 3-MCPDE. Repeated frying in the presence of antioxidants (TBHQ, rosemary and phenolics) decreased 3-MCPDE in processed food. The GE content in foods tends to decline with time, indicating instability of GE's epoxide ring.
The presence of 3-monochloropropane-1,2 diol ester (3-MCPDE) and glycidyl ester (GE) in processed palm oils is of concern, as these oils are widely used for edible purposes. The mitigation method studied here optimizes the removal of chloride through water washing of crude palm oil (CPO), to limit the formation of 3-MCPDE. The contaminant removal obtained via washing CPO supports the quantitative findings. By utilizing 5% water in the washing step, water-soluble chlorides in CPO are removed by up to 76%, resulting in a 71% reduction of 3-MCPDE to within statutory limits. In this study, a linear correlation was developed between the chloride and the corresponding 3-MCPDE with a correlation coefficient (R2) of 0.99. Using the correlations, 1.0 mg/kg of 3-MCPDE in refined, bleached and deodorized palm oil (RBDPO) will be obtained from CPO with 1.2 mg/kg chloride with 7% wash water usage. The study also showed minor GE reduction between 7 and 11% was attained after water washing.