Ching Lik Hii

Improving Malaysian cocoa quality through the use of dehumidified air under mild drying conditions

BACKGROUND Various studies have been conducted in the past to improve the quality of Malaysian cocoa beans. However, the processing methods still remain crude and lack technological advancement. In terms of drying, no previous study has attempted to apply advanced drying technology to improve bean quality. This paper presents the first attempt to improve the quality of cocoa beans through heat pump drying using constant air (28.6 and 40.4 °C) and stepwise (step-up 30.7-43.6-56.9 °C and step-down 54.9-43.9 °C) drying profiles. Comparison was made against hot air drying at 55.9 °C. RESULTS Product quality assessment showed significant improvement in the quality of Malaysian cocoa beans. Quality was found to be better in terms of lower acidity (higher pH) and higher degree of browning (cut test) for cocoa beans dried using the step-up profile. All heat pump-dried samples showed flavour quality comparable to that of Ghanaian and better than that of Malaysian and Indonesian commercial samples. Step-up-dried samples showed the best flavour profile with high level of cocoa flavour, low in sourness and not excessive in bitterness and astringency. CONCLUSION Dried cocoa samples from the step-up drying profile showed the best overall quality as compared with commercial samples from Malaysia, Indonesia and Ghana. The improvement of Malaysian cocoa bean quality is thus achievable through heat pump drying.

Optimization of Heat Pump–Assisted Intermittent Drying

In the present study, heat pump–assisted drying of salak fruit was optimized by dividing the dehydration process into three distinct phases, namely, the initial, intermittent, and final stages. Drying variables considered for the optimization were the intermittent duration (X 1), intermittent ratio (X 2), and intermittent cycle (X 3); the response variables studied were the total drying time (Y 1), total heating time during intermittent drying (Y 2), total heating time after intermittent drying (Y 3), total color change (Y 4), ascorbic acid content (Y 5), and total phenolic content (Y 6). Response surface methodology was used to determine the best combination of the drying variables that could provide the shortest drying period and premium product quality. Experimental results showed that all of the response variables were improved under the optimized intermittent drying conditions compared to the conventional method using constant drying conditions. The optimized heat pump–assisted intermittent drying reduced the drying time by 36% and improved phytochemicals retention with ascorbic acid and total phenolic content recorded at 18.4 ± 1.8 mg ascorbic acid/100 g dw and 43.3 ± 2.2 mg gallic acid equivalent (GAE)/g dw, respectively. The color change of the final product was minimum with a ΔE* value of 7.26 ± 2.03.

Effect of ambient conditions on drying of herbs in solar greenhouse dryer with integrated heat pump

ABSTRACT An even span solar greenhouse dryer was built and applied to dry Java tea (Orthosiphon aristatus) and Sabah snake grass (Clinacanthus nutans Lindau). Findings showed that the solar greenhouse dryer performs satisfactorily during clear weather except at nighttime and rainy day due to product rehydration which is heavily influenced by high relative humidity from ambient air. Integrating of heat pump into the solar greenhouse dryer has successfully reduced the room relative humidity by 10–15%. Also, heat pump has mitigated the product rehydration issue by maintaining room relative humidity at maximum of 65% throughout the drying period. The drying rate of Java tea was improved three to fourfold, i.e., from 0.004–0.008 to 0.018–0.025 g H2O/g DM min, whereas 10% of drying time was saved for both Java tea leaf and Sabah snake grass leaf with the assistance of heat pump system. Meanwhile, the supply of dry air from the heat pump system with a magnitude of 0.25–0.50 m/s helps in enhancing the drying rate of the herbs as well as minimizing the nonuniformity of drying temperature and relative humidity inside the solar greenhouse dryer.

Convective Air Drying of Raw and Cooked Chicken Meats

This research investigated the effects of convective air drying on the quality of raw and cooked chicken breast meats at 60, 70, and 80°C. Raw samples were cut into sizes of 20 mm × 20 mm × 7 mm and cooked samples were precooked in hot water and cut into similar sizes. It was observed that cooked samples had a lower initial moisture content and dried faster than the raw samples. The thicknesses of raw samples were observed to increase in the first 2 h due to internal water vapor generation. The rigid structure of the cooked samples resulted in a lower degree of shrinkage compared to the raw samples. Rehydration capacity was lower in the cooked samples, which could be due to the rigid structure resulting from the precooking process. This further reduced the imbibition of water into the sample. Effective diffusivity values were determined in the order of magnitude of 10−11 m2/s and comparable to those from the literature. Hardness values of dried cooked samples were significantly higher (p < 0.05) than the dried raw samples, whereas elasticity was significantly lower (p < 0.05).

Moisture Transport Mechanism and Drying Kinetic of Fresh Harvested Red Onion Bulbs under Dehumidified Air

Abstract Drying plays an important role in post-harvest handling of onion for prolonging storage time. This research focuses on the drying studies of red onion bulbs using dehumidified air. The works were carried out by observing the microscopic structure of red onion bulbs layer and followed by developing mass transfer model for moisture diffusion during drying. Moisture diffusivity was estimated from drying experiments conducted at various temperatures (40, 50 and 60 °C) using the unsteady state solutions of Fick’s second law model. The diffusivity values were used to predict the drying kinetics as well as effective drying time for different air relative humidity. Results showed that combination of low relative humidity and low drying temperature significantly improved drying rate and reduced drying time.

Effects of water blanching on polyphenol reaction kinetics and quality of cocoa beans

Several studies have been reported on the potential health benefits of cocoa polyphenols. However, drying has an inhibitory effect on the substantial recovery of cocoa polyphenols. This is majorly because of the high degradation of polyphenol compounds as well as the enhanced activity of polyphenol oxidases; a pre-cursor for browning of polyphenols during drying. Pre-treatment technique such as water blanching (80° and 90°C for 5 min, 10 min and 15 min exposure times respectively) can inactivate the polyphenol oxidases enzyme and promote high percent of the polyphenol recovery in dried cocoa bean. The degradation kinetics of cocoa polyphenols during hot water blanching are analyzed; The rate constant for the polyphenol degradation after blanching was found to be ranging from 0.0208 to 0.0340 /min. The results for dried fresh cocoa beans showed an optimal level of polyphenol recovery (118 mg GAE/g) when blanched at 90°C for 5 minutes duration. The antioxidant activity is also analyzed using DPPH scavenging...

Emerging macroscopic pretreatment

Macroscopic pretreatment of food waste aims at the preparation of the food matrix for subsequent processing and recovery steps. The preparatory steps involve the adjustment of the phase content and properties (water, solid, fats content), the moderation of enzyme activity as well as prevention and control of any microbial growth (Galanakis, 2012; Galanakis et al., 2010a). In recent times, several emerging technologies have been researched, developed, and/or adapted from other fields for drying, sterilization, enzyme inactivation, and enhancing mass transfer in food and biomaterials. This chapter focuses on these upcoming technologies with potential applications to food waste recovery and includes foam-mat drying, electro-osmotic drying, radio-frequency drying, cold plasma technology, and high-pressure processing. The content lays emphasis on discussing the successful applications and identification of future prospects, from both a technology and an economic point of view.

Effects of drying on the production of polyphenol-rich cocoa beans

ABSTRACT The current study emphasizes on the effects of four drying methods, namely, oven drying, adsorption drying, freeze-drying, and vacuum drying on the total polyphenol content and antioxidant activity of unfermented cocoa beans. The comparison of drying kinetics analysis showed that adsorption drying method dried faster than other methods. On comparing the results of total polyphenol contents and antioxidant activity, freeze-drying method showed the optimal results and the lowest values were recorded by oven drying. The sensory analysis of cocoa beans after drying showed low cocoa flavor and high astringency scores.

Conference Report: The 2nd International Symposium on Processing and Drying of Foods, Vegetables and Fruits, June 18–19, 2012, University of Nottingham, Malaysia Campus, Semenyih, Selangor, Malaysia

The 2nd International Symposium on Processing and Drying of Foods, Vegetables and Fruits (ISPDFVF 2012) was successfully organized by the Center for Food and Bio-products Processing and The Faculty of Engineering, University of Nottingham, Malaysia Campus (UNMC) from June 18–19, 2012. The International Advisory Board was chaired by Professor Arun S. Mujumdar (Minerals, Metals, and Materials Technology Center, National University of Singapore, Singapore) and co-chaired by Ir Professor Law Chung Lim (UNMC) while the Local Organizing Committee was chaired by Dr. Hii Ching Lik (UNMC) and co-chaired by Dr. Ong Sze Pheng (UNMC). The first symposium was held last year in the UNMC Kuala Lumpur Teaching Center (April 11–12, 2011).