臺灣博碩士論文加值系統

在青鱗魚這一類屬於鯡魚科的小型高脂魚類中，不管以冷藏或冷凍的方式進行保存，其仍然無法具有較長的保質期，而為了確保貯存的生魚能供給消費者食用，因而有必要對青鱗魚的鮮度品質進行徹底評估。由於小型青鱗魚具有較易腐敗的特性，因此在捕撈後會立即將其加工處理成乾燥產品，並以此形式在市場上銷售。而本研究的目的便是要比較以烘箱乾燥及日曬乾燥進行小型青鱗魚的處理時，對其鮮度與乾燥條件的影響，同時也會觀察不同大小的生鮮青鱗魚在營養成分含量上的差異及其於 -20℃ 下冷凍貯藏期間的鮮度品質變化，以評估消費者食用時的安全性。本實驗的研究結果顯示，相較於魚肉的部份，在全魚中具有顯著較高的灰份含量，此顯示魚體中的礦物質主要是存在於肌肉以外的部份，因此建議在製造小型青鱗魚的食品時，以保留全魚體的方式進行處理並供給消費者食用，如此可使產品具有較高的附加價值。而在 pH 及揮發性鹽基態氮 (Total volatile basic nitrogen, TVBN) 值的測定結果中顯示，不論青鱗魚的魚體大小，於 -20℃ 下貯存 6 個月後，其仍處於新鮮狀態，但在硫代巴比妥酸 (Thiobarbituric acid, TBA) 值上，結果指出魚體應在新鮮狀態或是貯存於 -20℃ 下的 1 個月內便將其食用完畢較佳。而以 80℃ 烘箱乾燥的青鱗魚，可發現其揮發性鹽基態氮值較日曬乾燥的組別高，然而其皆符合消費者食用的標準，且在 pH 及 TBA 值上也並未具有顯著差異。另外在感官品評的結果中，以 60℃ 及 80℃ 烘箱乾燥的組別，其較日曬乾燥組有較高的接受度。綜合以上實驗結果並考慮到便利性以及節省時間等相關因素後，採用 80℃ 烘箱乾燥的條件進行青鱗魚的乾燥處理被認為是可以用來取代傳統日曬乾燥的方法。

It is widely known that small-fatty fish like herring does not have long shelf life, even in chilled or frozen state. To make sure that the stored raw fish is still permitted for human consumption, the freshness of the bluestripe herring needs to be assessed thoroughly. Small-sized bluestripe herring spoils faster; therefore it is mostly processed into dried products right away and sold in the market in dried form. This present study aims to compare the drying process of small-sized bluestripe herring by oven and sun as the most often used methods in small fish drying and to observe the nutrition content of the different sizes-raw bluestripe herring and their freshness quality during frozen storage at -20ºC to assess its safety for human consumption. The significantly higher amount of ash in whole fish compared to meat part indicates that the minerals are deposited in other parts except meat, thus suggesting the benefit of utilizing small-sized bluestripe herring for human consumption as it is commonly processed and eaten as whole. pH and TVBN values indicate that bluestripe herring (all sizes) are still in fresh condition even after 6 month storage at -20ºC, but considering the TBA values, the fish are considered best to consume when fresh or at most before 1 month at -20ºC frozen storage. The fish oven-dried at 80°C gave higher TVBN amount than sun dried fish, however, both values are still considered suitable for human consumption. Their pH and TBA values did not show any significant difference. The fish oven dried at 60°C and 80°C had higher acceptance in sensory test compared to sun dried fish. Regarding to the convenience and time saving benefits, oven drying the fish at 80°C deserves to be considered as alternative to traditional sun drying method.

Table of Contents
1. INTRODUCTION…………………………………………...…………………1
2. LITERATURE REVIEW……………………………………...………………4
2.1. Characteristics of bluestripe herring (Herklotsichthys quadrimaculatus)
and other herring species…………………………………………...……………4
2.2. Nutritional content of fish……………………………………...…………...4
2.3. Frozen storage and spoilage in fish……………………………...………….7
2.4. Freshness analysis methods……………………………………..………....10
2.5. Fish drying……………………………………………………..…………..13
2.6. Sensory analysis…………………………………………………………...16
3. EXPERIMENTAL DESIGN…………………………………………………18
4. MATERIALS AND METHODS……………………………………………..19
4.1. Sample collection………………………………………………………….19
4.2. Nutrition assessment of raw bluestripe herring…………………………....19
4.2.1. Proximate analysis……………………………………………...19
4.2.2. Calcium analysis………………………………………………..22
4.3. Freshness analysis during frozen storage………………………………….23
4.3.1. pH measurement………………………………………………..23
4.3.2. TVBN analysis………………………………………………....23
4.3.3. TBA analysis…………………………………………………...24
4.4. Drying of bluestripe herring……………………………………………….25
4.4.1. Analysis of water activity (aw) and moisture content…………25
4.4.2. Freshness analysis of dried fish………………………………...25
4.4.3. Sensory analysis………………………………………………..25
4.5. Statistical analysis………………………………………………………….26
5. RESULTS AND DISCUSSION………………………………………………27
6. CONCLUSION………………………………………………………………..63
REFERENCES……………………………………………………………………65





List of Tables

Table Page
1. Proximate composition of whole bluestripe herring in wet weight basis….…29
2. Proximate composition of whole bluestripe herring in dry weight basis.……29
3. Proximate composition of bluestripe herring meat in wet weight basis.……..31
4. Proximate composition of bluestripe herring meat in dry weight basis………..32
5. Calcium content of dried small, medium, and big bluestripe herring………….32
6. Sensory properties of small bluestripe herring dried with oven and under sun...62



List of Figures

Figure Page
1. Generalized deterioration reaction rates in food system as a function
of water activity (room temperature)…………………………………………...14
2. Small, medium, and big-sized bluestripe herring in length…………………….27
3. Comparison of proximate composition between meat and whole
small-sized herring……………………………………………………………..33
4. Comparison of proximate composition between meat and whole
medium-sized herring…………………………………………………………..34
5. Comparison of proximate composition between meat and whole
big-sized herring………………………………………………………………..35
6. pH changes of small-sized bluestripe herring during frozen storage…………..36
7. Changes of TVBN value in small-sized bluestripe herring during frozen
storage…………………………………………………………………………..37
8. Changes of TBA value in small-sized bluestripe herring during frozen
storage…………………………………………………………………………..38
9. pH changes in medium-sized bluestripe herring during frozen storage………..41
10. Changes of TVBN value in medium-sized bluestripe herring during
frozen storage………………………..…………………………………………42
11. Changes of TBA value in medium-sized bluestripe herring during
frozen storage…………………………………………………………………..43
12. pH changes in big-sized bluestripe herring during frozen storage……………..45
13. Changes of TVBN value in medium-sized bluestripe herring during
frozen storage……………………………………………………………….….46
14. Changes of TBA value in medium-sized bluestripe herring during
frozen storage……………………………………………………………….….48
15. Freshness values comparison of meat and whole small-sized bluestripe
herring after 6 months frozen storage…………………………………………..50
16. Freshness values comparison of meat and whole medium-sized
bluestripe herring after 6 months frozen storage……………………………….51
17. Freshness values comparison of meat and whole big-sized bluestripe
herring after 6 months frozen storage…………………………………………..53
18. Freshness values comparison between sun-dried and 80°C-oven-dried
small bluestripe herring………………………………………………………...55
19. Freshness values comparison between small bluestripe herring dried in
60°C and 80°C oven dryer……………………………………………………...57
20. Changes of aw (a) and moisture content (b) of small-sized bluestripe
herring during oven drying at 60ºC…………………………………………….58
21. Changes of aw (a) and moisture content (b) of small-sized bluestripe
herring during oven drying at 80ºC…………………………………………….60
22. Changes of aw (a) and moisture content (b) of small-sized bluestripe
herring during sun drying…………………………………………………..…..61

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