由脫脂芝麻粕製備蛋白質濃縮物之研究

Abstract

芝麻粕是芝麻製油工業的副產物，脫脂芝麻粕的蛋白質含量可達40~50%。為落實副產物再利用之理念，本研究參考大豆蛋白產品之製備方式，以黑芝麻粕(defatted sesame meal, DSM) 為原料，透過酵素預處理(enzyme pretreatment)及鹼萃取-pH調整沉澱法 (alkaline extraction, followed by pH swing for protein recovery) 的處理方式以進行芝麻蛋白的製備。在樣品預處理的部分，首先主要可分為兩種：未經酵素預處理 (DSM) 與經由商業化酵素(Viscozyme®L) 預處理之固形物樣品（E-DSM），再分別進行後續鹼萃取- pH調整沉澱法以製備芝麻蛋白。第一步先探討鹼萃取-pH調整沉澱法之最適條件，鹼液為0.1 N NaOH、萃取時間為60 min、樣品與鹼液之比例為1：30 及pH 為4.0。在此最適條件下，從DSM所製得之芝麻蛋白 (DSM-P)，其蛋白質含量為61.2%，回收率為51.9%，而E-DSM所製得之芝麻蛋白 (E-DSM-P)，雖其蛋白質含量提高至66%，回收率為65%。 但也發現，酵素預處理的部分無論其酵素使用量的多寡，皆對於蛋白質含量與回收率無顯著差異。此外，於鹼萃取-pH調整沉澱法之結果發現，在無添加鹼之情況下，即有部分水溶性蛋白質溶出，因此本研究延伸出以熱水洗預處理 (hot washing pretreatment)，再以鹼萃取-pH調整沉澱法處理，期望能以簡便的方式來提高蛋白質含量。結果顯示，相較於DSM-P，經熱水洗預處理後之固形物樣品 (Prewashed-DSM) 在最適鹼液處理之條件下製備之芝麻蛋白(Prewashed-DSM-P)，其蛋白質含量明顯提高為67.9%，回收率為59.1%。然而，經熱水洗及酵素預處理之固形物樣品(E-Prewashed-DSM)經鹼液處理後，其芝麻蛋白產品 (E-Prewashed-DSM-P) 之蛋白質含量卻只有61.2-64%。綜合以上四種蛋白質產品之結果，本研究之最適條件Prewashed-DSM，具有較高之蛋白質含量及回收率。另外， 以脫脂白芝麻粕(defatted white sesame meal, DWSM) 為原料，經鹼萃取-pH調整沉澱法之最適條件下所製得之芝麻蛋白 (DWSM-P)，其蛋白質含量為84.1 %，回收率為52.2 %。由此結果得知，利用鹼萃取-pH調整沉澱法進行芝麻蛋白的製備是可行的，但蛋白質產品的品質會受到原料的影響，而有所不同。

Defatted sesame meal (DSM) is a by-product obtained from sesame oil expelling process. The protein content of DSM will reach approximately 40-50% as the potential source of plant protein. Based on efficient utilization of by-products, the present study has focused on the preparation of protein concentrate from DSM by using enzyme pretreatment and alkaline extraction, followed by pH swing for protein recovery from alkaline extract. First, the optimization of alkaline extraction and pH swing for protein recovery that could be recovered from DSM was investigated. The results showed that the optimum conditions for alkaline extraction and protein precipitation were 0.1 N NaOH solutions at the ratio of 1: 30 (w/v) for 60 min and precipitated at pH 4.0. Protein product (DSM-P) prepared from DSM under optimum conditions, its protein content was 61.2% and protein recovery was 51.9%. In addition, ultrafiltration was also feasible to prepare protein product by concentrated and desalting. Second, the feasibility of the enzyme, Viscozyme®L used to facilitate protein extraction in this study was evaluated because the fiber might hinder the protein extraction. The sample with enzyme pretreatment (E-DSM) was served as starting material for the preparation of protein products. Protein product (E-DSM-P) prepared from E-DSM, its protein content was increased to 66% and the protein recovery was around 65%. For the outcome of enzyme pretreatment prior to alkaline extraction, the results indicated that there was no significant correlation between the amount of enzyme used and the protein content and protein recovery of the protein product. In addition, approximately 23% of total protein extracted from DSM without using alkaline solution at the ratio of 1:10 (w/v) was observed. Thus, the effect of hot washing pretreatment prior to enzyme pretreatment and alkaline extraction on the preparation of protein concentrates was studied. The sample with hot washing pretreatment (Prewashed-DSM) was subsequently served as starting material. In comparison to DSM-P, the protein content of protein product (Prewashed-DSM-P) prepared from Prewashed-DSM without enzyme pretreatment could reach 67.9% and protein recovery was 59.1%. Moreover, the effect of enzyme pretreatment after hot washing pretreatment, followed by alkaline extraction and protein precipitation on the preparation of protein concentrates was investigated. The result showed that the protein content and protein recovery of the protein product (E-Prewashed-DSM-P) was 63-64% and around 60% respectively. It indicated that use of enzyme pretreatment prior to alkaline extraction for the preparation of protein concentrates might not significantly improve the protein content. According to the overall results, a comparison of protein content and protein recovery between four protein products (DSM-P, E-DSM-P, Prewashed-DSM-P and E-Prewashed-DSM-P) was made. Taking cost and efficiency together with the present analytical results into consideration, we suggested that hot washing pretreatment prior to alkaline extraction would be an effective method to prepare protein concentrate from DSM which in the range of 65-68% protein content. Last, the preparation of protein products from defatted white sesame meals (DWSM) has studied. The protein content and protein recovery of the protein products (DWSM-P) prepared from DWSM were approximately 84% and 52.2% respectively. From the result, it concluded that the quality of final protein product varied depending on the starting materials and processing condition.