- 學位論文
不同乾燥條件對重組肉乾脂肪氧化與風味口感之研究
Study of lipid oxidation and eating quality of restructured pork jerky under different drying conditions.
摘要
風味是影響肉製品品質重要的因素之一，通常也是決定消費者是否購買的參考依據。肉製品的風味一般來自於烹調/加熱處理所引發的化學反應，過去有文獻指出加熱過程所造成的脂肪氧化，是促進肉製品產生風味的重要原因，但亦有部分研究指出加熱會導致肉製品風味降低。儘管如此，加熱對於肉製品風味的產生還是扮演著關鍵的角色。在此觀點下，研究肉乾製品脂肪氧化程度與與風味間的關係至為重要。因此本研究利用豬後腿肉為原料，分為兩個處理組：有添加保濕劑(humectant)與無添加保濕劑，將其製成豬肉重組肉乾(RPJ)，在50°C條件下以循環烘箱分別乾燥3、4、5小時後，再分別以180°C烤箱加熱至中心溫度達80°C。分析項目有：pH值、水分、水活性、脂肪氧化、色澤、截切值、官能品評。結果顯示：隨著乾燥時間增加，水分與水活性會顯著地下降，不同乾燥條件會顯著影響最終豬肉乾的品質。添加保濕劑處理組有較高的水分含量與較低的水活性，但有無添加保濕劑在乾燥5小時，皆有最低的水分含量與水活性(有添加保濕劑-RPJ5-S：水分36.76%、水活性 0.87；無添加保濕劑-RPJ5：水分35.15%、水活性 0.89)。在色澤部分，RPJ4有最低的亮度值(L*)，但在RPJ5-S反而有最高的亮度值，而紅色值(a*)則是RPJ4最高，RPJ5-S卻是最低。在截切值方面，隨著乾燥時間增加各處理組皆會增加製品的硬度，且添加保濕劑處理組顯著較未添加保濕劑處理組有較低的硬度，較低的截切值出現在RPJ4(2.34 kgf/mm2)、RPJ4-S(1.80 kgf/mm2)，較高的皆切值則在RPJ5(3.71 kgf/mm2)和RPJ5-S(2.85 kgf/mm2)。此外，保濕劑處理組以RPJS-5具有最高的TBARS 值(14.05 mg MDA / kg)，未添加保濕劑處理組則是以RPJ-4有最高的TBARS值(16.77 mg MDA / kg)。在感官品評結果顯示，分別以RPJS-5與 RPJ-4有最高的香氣、風味與總接受性得分。綜合以上結果可知，肉乾製品的脂肪氧化確實與風味、接受度有相關，但對於脂肪氧化與風味生成之間的機制，仍需持續進行的研究來找出確切原因。
並列摘要
Flavor is one of the important factors affecting the quality of meat products, and it is often an critical reference basis for consumers to purchase. The flavor of meat products generally comes from the chemical reaction caused by cooking/ heating treatment, and there have been literatures in the past that lipid oxidation caused by heating process is an important reason for promoting the flavor of meat products, but some studies have pointed out that heating can lead to a decrease in the flavor of meat products. Nevertheless, thermal treatment plays a key role in the production of meat flavor. From this point, it is important to study the relationship between lipid oxidation degree and flavor of dried meat products. Therefore, this study uses pork hind legs meat as raw material, divided into two treatments groups: first group was added with sorbitol (humectant) and second group without sorbitol, made into restructured pork jerky (RPJ), in 50°C conditions to circulating oven drying 3, 4, 5 hours, and then roasted in an oven at 180°C to reach a center temperature of 80°C. The analysis items include pH, moisture, water activity, lipid oxidation, color (CIE L*, a*, b*), shear value and sensory quality evaluation. The result showed that with the increase of drying time, the moisture and water activity decreased significantly, and different drying conditions significantly affected the quality of the final pork jerky. However, higher moisture content and lower water activity found in samples added with sorbitol, but both samples (with and without sorbitol) had lower moisture content and water activity (36.76%, 0.87 and 35.15%, 0.89 in RPJ5-S and RPJ5, respectively) at the end of processing. Color properties demonstrated lower L* value (lightness) in RPJ4 but high in RPJ5-S, while a* value (redness) was high in RPJ4 and low in RPJ5-S. The lowest shear force values (SFV) were recorded in samples with sorbitol compared to high SFV in those without sorbitol. Lower and higher SFV (2.34, 1.80 kgf/mm2 and 3.71, 2.85 kgf/mm2) recorded in RPJ4, RPJ4-S, and RPJ5, and RPJ5-S, respectively. In the results of the sensory evaluation, the highest aroma, flavor and total acceptance scores were scored by RPJS-5 and RPJ-4, respectively. Comprehensive results show that the lipid oxidation of dried meat products is indeed related to flavor and acceptance, but the mechanism between lipid oxidation and flavor generation still needs to be studied continuously to find out the exact cause.