Effect of Osmotic Dehydration as a Pre -Treatment on Air Fried Sweet Potato (Ipomoea batatas) Chips

Air frying is a modern frying technique that promises low oil content of fried products. However, the main limitation of air frying is that it requires a longer operating time than deep fat frying. Previous studies found that osmotic dehydration is beneficial as frying pre-treatment to improve the quality of fried products and reduce frying time, but to date, there is no study investigating its application in air frying. Therefore, this study aims to examine the effect of osmotic dehydration as pre-treatment on the quality of air-fried sweet potato chips. Sweet potatoes were cut into slices with the same thickness, and then soaked in distilled water, 5% sodium chloride solution, and 10% sodium chloride solution for one hour. The potato slices were then air fried at two temperatures: 160˚ and 180˚C for 3, 6, 9, 12, and 15 minutes. Then, moisture content, colour, texture, diameter shrinkage and thickness expansion were analysed. The moisture content of air fried chips decreased with the increasing of frying time. The osmo-dehydrated sample showed lower moisture content which could the reduce frying time from 12 mins to 9 mins at 160ºC. Osmo-dehydrated sweet potato slices produce paler chips, but the treatment preserved the red and yellow colour of the sample. Air fried sweet potatoes that were osmotically dehydrated samples shrank more in diameter than the control samples. The increased thickness of chips was caused by crust formation and the bubbles formed at the surface due to the barrier formed by the tight surface, resulting in vapour expansion inside the pores of the chips. The hardness of pre-treated chips increased significantly with decreasing moisture content. Using osmotic dehydration pre-treatment in the air frying process can yield promising results in less frying time and better retention in terms of red and yellow colour

Physical properties of kelulut honey emulsions with different oil types and emulsifier concentrations

Kelulut honey (KH) is a honey produced by stingless bee species, known for its high nutritional content and health benefits. Even though it is very healthy, some people cannot consume it directly. Therefore, incorporating this type of honey into an emulsion system is a good strategy to increase its consumption. Emulsion technology is one of the alternative technologies nowadays which combines two or more immiscible liquids to form a solution. In this study, KHemulsions were emulsified with glyceryl monostearate (GMS) and stabilised by xanthan gum. There were two stages involvedto determine the effects of variations in oil types and emulsifier concentrations on the physical properties of KH emulsions. In the first stage, three types of oil were used as the dispersed phase, which were palm oil, canola oil, and sunflower oil. Then in the second stage, different concentrations of GMS (0.25, 0.5, 0.75 and 1%) were applied. From the droplet size analysis, the emulsion with sunflower oil and the highest concentration of GMS gave the smallest diameter of 0.78 ± 0.01µm and the lowest polydispersity index (pdI) of 16.2±2.03 %. Meanwhile, the texture analysis shows that emulsion with palm oil has the highest firmness (45.16±2.83 g) and consistency (305.44±14.91 g.sec) values. The foaming index on the other hand depicts that emulsion with palm oil and that with the lowest concentration of GMS gave the highest foam stability. From this study, a physically stable oil-in-water KH emulsion was produced, which should undergo further chemical, sensory and storage studies for commercial production in the future

Impact of Using Alternative Sweetener as Osmotic Agent on Mass Transfer, Colour and Texture Properties During Dip Dehydration of Apple Slice

Previous study has explored dip dehydration as a novel variant of osmotic dehydration to reduce solid gain, which is the main problem of osmotic dehydration. However, this dehydration process commonly uses sucrose solution as osmotic agent which might contribute to the increase in glycaemic index and can also be linked to different diseases such as diabetes and obesity. Therefore, this study aims to investigate the effect of using alternative sweeteners as an osmotic agent on mass transfer, colour, and texture profiles during dip dehydration of apple slices. Three alternative sweeteners, i.e., erythritol, sorbitol and xylitol with 30% (w/v) concentration were used in this study. Apple slices with 1.5 mm thickness and diameter of 55 mm were dipped multiple time in the same concentrated solution every 40 minutes until 200 minutes before samples were analysed. Findings showed that different type of sweetener affect water loss and solid gain. Xylitol and sorbitol gave highest water loss about 36% and 40%, respectively. Lowest total colour different with fresh apple has been observed in sample treated with xylitol. As for texture, there is no remarkable effect of using alternative sweetener as osmotic agent at all processing times. Overall, the best alternative sweetener for sucrose is xylitol considering the mass transfer and quality of apple slices

Effect of Salt Addition on Mass Transfer, Colour and Texture Characterictics of Shallow Fried Potato Strips

Shallow frying is widely used as one of the cooking processes because of its simplicity and ability to gives better taste of foods by adding spices, herbs and salt. Despite its widespread use, the mass transfer and product properties of shallow frying have not been studied systematically, especially after the addition of salt. This study aims to investigate the effect of adding salt to potato strips, prior to shallow frying on the mass transfer (moisture and oil contents) and physical properties (colour and texture) of products. The potato strips were cut into 9 x 9 x 50 mm and were divided into salted (1% w/w) and unsalted (as control), and then were shallow fried at 150°C and 180°C for 35 minutes. The moisture and oil contents were analysed every 5 minutes, while colour and texture were determined at the end of shallow frying (i.e. when moisture content reached ~0.82 kg H2O/kg dry matter). Salted fried potato at 180°C resulted in a significantly shorter frying time of 18 minutes, compared to unsalted fried potato, which took 21 minutes. Meanwhile, at 150°C, the frying time reduced to 25 minutes for the salted product from 33 minutes under unsalted product. The oil content, colour and texture of final products were not significantly different under both treatments. Therefore, the effect of adding salt to potato strips does not influence the oil content, colour and texture of the shallow fried products, but reduces frying times by up to 24%, thereby improving energy efficiency

Process control of pink guava puree pasteurization process: simulation and validation by experiment

Recently, process control has been applied extensively in many food processes include pasteurization process. The purpose is to control and maintain the product temperature at desired value. In order to be able to control the process properly, the model of the process needs to be obtained. This research aims to obtain the empirical model and to determine the best control strategy in pasteurization process of pink guava puree. The PID controller tuned by different tuning methods was simulated using Simulink and closed loop responses were observed. Simulation results revealed that PID controller tuned by minimizing of integral absolute error (IAE) method were satisfactory adaptable in this process in term of faster settling time, less overshoot, smallest values of IAE and ISE that less than 1. Then, experiment was performed using this method in order to validate simulation results. In general, a good agreement was achieved between experimental data and dynamic simulation result in control of pasteurization temperature process with R2=0.83. As the conclusion, the results obtained can be used as the recommendation for a suitable control strategy for the pasteurization process of pink guava puree in the industry

Modeling, simulation and control of pink guava puree pasteurization process with fouling as disturbance

Fouling is an unwanted deposit on a heat exchanger surface which may cause inefficiency to the heat exchanger's performance in maintaining the outlet product temperature during pasteurization. In order to deal with this problem, fouling must be handled by an efficient control strategy. In this study, an empirical model of fouling was successfully developed and used in a control system. The obtained model is represented by first order plus time delay model with R2 = 0.90. Several proportional-integral-derivative (PID) controllers were then simulated on this model to determine the best control system. Simulation results showed that an ideal PID controller tuned by minimization of integral absolute error (IAE) method exhibited good performance in disturbance rejection of fouling with settling time reduced and robustness improved. This result provides insights to properly design a control strategy dealing with fouling during pasteurization. Pasteurization is one of the food preservation techniques which is commonly applied in beverage and food industries. The outlet product temperature from this process is a crucial parameter that must be controlled to satisfy the industrial standard. However, fouling deposit that occurs during pasteurization process hinders the temperature from reaching the desired value. Hence, a good controller should be designed in order to address this issue. In this study, a control strategy was investigated to deal with fouling problem by using simulation work. The simulation results obtained can be integrated in control strategy design for beverage and food industries. Furthermore, with an enhanced control strategy, product quality is ensured as well as improving efficiency in plant's energy consumption

Dehydration of potato slices following brief dipping in osmotic solutions: effect of conditions and understanding the mechanism of water loss

A novel variant of osmotic dehydration, named here as post-dipping dehydration – where a material is dipped in a salt or sugar solution for a very short time followed by simple exposure to ambient conditions was explored with the aim of lowering water content of potato slices but at the same time not gain a high level of sugar/salt. The rate of water loss, which was rapid initially, was found to approach equilibrium. This paper also explored whether the water loss process could subsequently be kick started once again, by employing a multi-stage process, where each stage consisted of osmotic solution dipping followed by ambient holding of the potato slices that had reached equilibrium in the earlier stage. Water loss values comparable to conventional osmotic dehydration could be achieved thus, but with significantly lower overall solid gain (less than 50%) – which can potentially yield a significantly healthy product option

Microbiological and Physicochemical Analysis of Keropok lekor at Three Storage Temperatures

Keropok lekor is a one of a popular traditional food in east coast of peninsular Malaysia specifically in Terengganu. However, it is known to be highly perishable when stored at ambient temperature. This study aimed to investigate the microbiological and physicochemical quality of keropok lekor stored at ambient and refrigerated temperature. Samples of keropok lekor were collected from a local premise located in Besut, Terengganu and were packaged either ordinary sealed or vacuumed. The samples were stored at ambient (25℃-28℃), and refrigeration temperature (0℃-4℃) for up to 7 days. Microbiological analysis was performed using spread plate method and physicochemical analysis such as moisture, colour, pH and texture. The keropok lekor stored at ambient temperature showed significant increase in microbial count after one day for both vacuum and ordinary sealed pack at 6.18 log cfu/g and 7.85 log cfu/g, respectively. Refrigerated samples also showed significant increase after 7 days. The samples did not exhibit significant changes with regards to moisture, colour and hardness but pH was significant decrease during the storage which shows sign of spoilage. However, the keropok lekor chewiness significantly increased during storage. In conclusion, ambient temperature shows rapid spoilage of keropok lekor regardless of the packaging and refrigerated condition can extent the shelf life to 2 days for ordinary sealed samples and 3 days for vacuum samples

Novel and less understood methods of food dehydration: understanding the effects of process conditions and the mechanisms of water loss

Dehydration is one of the oldest food processing operations. It continues to be extensively employed today, and all indications point to its continued use in the foreseeable future. There are several dehydration techniques available for use in domestic and commercial practice. The main objective of this thesis is to focus on novel and less studied variants of two specific dehydrating methods: 1. Osmotic dehydration and 2. Frying. Osmotic dehydration is a natural process where water loss occurs by osmosis when food is brought into contact with a concentrated salt or sugar solution. Although this process consumes lower energy than other drying methods - which predominantly involve supplying the necessary latent heat for water evaporation from the food - a key problem is the high salt/sugar uptake which potentially poses health issues. In this thesis, a novel variant of osmotic dehydration called post-dipping dehydration – has been developed and studied. The technique involves dipping, say, potato slices, briefly in an osmotic solution, withdrawing it and allowing the water released to evaporate and/or drain under ambient conditions. The aim is to promote water loss just as in osmotic dehydration, but at the same time, minimize the uptake of the osmotic solute. The effects of osmotic medium concentration and dipping time on the water loss were initially investigated. Dipping potatoes in a higher concentration of osmotic solution was found to enhance post-dripping water loss, but the dipping time had no significant effect. Post dipping dehydration was also conducted as a multi-stage operation by repeatedly dipping potato slices in the osmotic solution followed by ambient exposure for a time period. The resulting water loss was comparable to osmotic dehydration but the uptake of the osmotic solute was significantly lower (less than 50%). In the next part of the research, multi-stage dip dehydration was investigated as a pre-treatment prior to frying potato chips, in order to evaluate its effect on the product quality. Multistage dip dehydration was found to decrease the frying time considerably which also resulted in about 17% lesser oil in the product. Colour measurements showed that the pre-treated samples were brighter and suffered lesser browning than blanched samples. The final part of this thesis is dedicated to gaining insights into shallow frying of potato and chicken cubes – an extensively employed but less understood dehydration operation in relation to deep-fat frying. The experimental investigations involved determining transient temperature variations during the process, moisture loss, oil uptake and the development of product texture. A key outcome of this research was the observation that the significant amount of water released initially from the food tended to form an oil-in-water emulsion, which subsequently boiled off to result in a phase inversion (i.e. the formation of water-in-oil emulsion). The temperature clearly increased after the phase inversion when the crust and texture of the end-product were formed

Effects of Sous-vide Cooking on the Initial Yield, Peak Force, and Elastic Modulus of Cooked Beef Semitendinosus

The objective of this study was to compare the traditional cooking method with sous-vide cooking at various cooking temperatures and times on the initial yield, peak force, and elastic modulus of semitendinosus (ST) beef. This study also examined the colour properties, cooking loss, and water retention of ST beef. Sous-vide samples were cooked inside vacuumized pouches at temperatures 60, 70, and 80 ℃ for 3 and 6 h. Meanwhile, the traditional cooking method was treated at 90℃ for 30 min. Reduced the initial yield, peak force, and elastic modulus of ST beef could be attained in 6 h at 60 ℃. Higher temperature and prolonged cooking time seem to cause meat to be tougher, likely due to the longitudinal myofibrils shrank. In terms of water retention and cooking loss, sous-vide cooked at 60 °C (regardless of cooking time) significantly exhibited better water retention and lower cook loss. This mild cooking temperature also best preserved the colour properties of lightness (L*) and redness (a*) than the other treatments