Improvement of quality characteristics of Indian mackerel (Rastrelliger kanagurta) by solar drying | |
| Author | Ramdas, Chavan Balu |
| Call Number | AIT Diss. no.AQ-08-05 |
| Subject(s) | Mackerels--Solar drying Solar dryers |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Aquaculture and Aquatic Resources Management, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Abstract | This dissertation presents a series of studies conducted to improve quality characteristics of dried Indian mackerel (Rastrelliger kanagurta) by solar drying. Prior to designing the experiments, field survey was conducted to assess the socio-economic conditions of small scale fishers in Maharashtra, India. The survey revealed that lack of proper drying technology as a major constraint reflected by the weighted mean index. Evidently, the traditional fish drying has become a problem as it is critical for improvement of quality of dried fish, and therefore, to effectively address the problem suitable fish drying system must be introduced. Hence, this research is conducted to develop cost effective method for drying of mackerel. Drying trials of mackerel in hot-air dryer were conducted to determine drying characteristics, optimum drying temperatures and time required for drying. The results showed that temperatures 46°C and 52 °c with 38 and 30 hours drying time, respectively gave the most satisfactory quality. Eleven different drying models were compared on the basis of high coefficient of determination (R²), minimum values of root-me an-square error (RMSE) and reduced chi-square (X²) between the experimental and predicted values of moisture ratios to explain the drying behavior of mackerel in hot-air dryers. It was found that at the drying temperatures of 46°C and 52 °c in hot air dryer gave the highest R² (0.999 and 0.998, respectively) and the lowest RMSE (0.0027 and 0.0096, respectively) and X² (0.000078 and 0.000631, respectively). The difference between the experimental and predicted values of moisture ratio was minimum, showing that the models satisfactorily describe the characteristics of drying process at 46°C and 52°C with 38 and 30 hours drying time, respectively. In this study the most acceptable taste, texture, odor, appearance and overall acceptability was found at 46°C and 52 0c. Contour plot of sensory evaluation of dried mackerel showed that optimum points for all attributes evaluated were at temperatures ranged from 46-52 °c with 38 and 30 hours drying time. Notably, for all sensory attributes examined panelists preferred fish dried at 46-52 °c. A series of drying experiments were carried out by using solar cabinet dryer (SCD), solar-biomass hybrid cabinet dryer (S-BHCD), biomass cabinet dryer (BCD) and open sun drying (OSD). The results of different drying models showed that all models produced good correlations; however, Midilli and two term drying models were the best fitted one and could be used to precisely predict the moisture content of dried mackerel in SCD, S-BHCD, BCD and OSD, respectively. The lowest RAISE, X² and highest R² values were found by Midilli drying models in SCD, S-BHCD, BCD to achieve the final moisture content <17% (w.b.). The overall drying efficiency of the solar cabinet dryer, solar-biomass hybrid cabinet dryer and biomass cabinet dryer was estimated to be about 19.77, 6.46 and 4.84 %, respectively. The quality of dried fish was evaluated by moisture content, variations of biochemical and microbial parameters, and sensory evaluation of dried fish. Drying methods such as SCD, S-BHCD, and BCD had significant effect (P <0.05) on the biochemical and microbial properties of dried mackerel. The experimental drying methods found coefficients of determination (R²) were >0.90, except TBA value. Contour plots of dried mackerel showed that for all sensory attributes examined, panelists preferred fish dried with SCD and S-BHCD. Storage study of dried mackerel showed that the dried product in SCD and S-BHCD remained in prime acceptable form after 120 days of storage at ambient temperature. A series of drying trials conducted in solar tunnel dryer (STD), solar-biomass hybrid tunnel dryer (S-BHTD) and open sun drying (OSD), in the third experiment. By considering the drying models, it is observed that the Midilli, Page and two term drying models found highest R² (0.9928), (0.9818), (0.9997) with lowest X² (0.000406), (0.00013), (0.000431) and RMSE (0.0164), (0.0120), (0.0119), respectively to achieve the final moisture content <17% (w.b.). The drying time required in STD and S-BHTD was 27 and 21 h respectively. The overall drying efficiency of the solar tunnel dryer, solar-biomass hybrid tunnel dryer and is estimated to be about 19.87 and 5.42%, respectively for fish drying. STD and S-BHTD have significant effect (P<0.05) on biochemical and microbial properties of dried mackerel. Biochemical analysis showed that the mackerel dried in STD and S-BHTD gave high coefficients of determination (R²>0.85), except histamine value. Contour plots of dried mackerel also showed that for all sensory attributes examined, panelists preferred fish dried with S-BHCD and SCD. During storage study: biochemical, microbial analysis and sensory evaluation showed that the dried mackerel remained in acceptable form after 120 days of storage period at ambient temperature. The result showed that the STD, S-BHTD produced high quality dried mackerel. However, by improving the design (larger size) of biomass stove will help to utilize the complete biomass energy and enhance drying efficiency. The financial analysis showed that the use of SCD, S-BHCD, BCD, STD, and S-BHTD is viable and profitable. The pay back period of all the experimental dryers was less than 1.5 years. The shelf-life of dried mackerel increased double (> 120 days) when compared with that of the dried mackerel from local fish markets «43 days). Finally, it is recommended that the SCD, S-BHCD, STD and S-BHTD can be used to produce high quality dry fish products and thus, may help the fisherfolk in India in producing high quality dried fish products. |
| Year | 2008 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. AQ-08-05 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Aquaculture and Aquatic Resources Management (AQ) |
| Chairperson(s) | Yakupitiyage, Amararatne; |
| Examination Committee(s) | Kumar, Sivanappan;Sakamon Devahastin;Athapol Noomhorm;Rakshit, Sudip Kumar;Yang, Yi; |
| Scholarship Donor(s) | Government of Maharashtra, India;Asian Institute of Technology Fellowship; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2008 |