醬油粕之回收利用及醬油醪和大豆蛋白水解之探討

Abstract

本論文針對目前醬油產業之問題及待改進項目進行探討與分析，包括下列三部份： 1. 醬油粕之回收利用 由於科技之進步及生活水準之提高，醬油粕作為飼料用途之比例日漸減少，如將其直接丟棄或焚燒處理，更會對環境造成污染。其實醬油粕中尚含有許多有用之成分如胺基酸、纖維素、異黃酮等，具有回收再利用的價值。在製備脫鹽醬油粕的過程中，所產生之水洗鹽液含有豐富胺基酸等營養成分，若直接排放，亦會造成環境污染。本研究目的之一為探討將此水洗鹽液回收再利用之可行性，進而使醬油粕之回收利用更加完善。本研究利用醬油粕水洗液作為醬油釀造之鹽水來源，經過六個月之釀造，水解率可達59.3 %，較未使用醬油粕水洗液釀造醬油之水解率(56.7 %)高出2.6 %；使用醬油粕水洗液釀造醬油之總氮利用率可達83.6 %，較未使用醬油粕水洗液之總氮利用率(79.7 %)高出約4 %，此增加之4 %總氮利用率根據計算推測係來自醬油粕之水洗液。本研究結果證實利用醬油粕水洗液釀造醬油之可行性，而且可有效利用醬油粕水洗鹽液中之食鹽及胺基酸，除了可降低所需之食鹽成本外，亦能增加醬油之產率。 2. 利用嫌氣發酵方式提升醬油醪之水解效率 醬油所需要之釀造時間極長，通常為六個月至一年，若能有效提高醬油醪發酵水解之效率，則可以減少醬油生產所需要的時間，進而減少成本，同時提高生產效率。過去研究發現蛋白酶活性受溫度以及鹽分含量之影響甚大，因此，本研究擬在無鹽條件下配合嫌氣條件進行醬油醪之發酵，在不同溫度下探討其水解率之經時變化，期望能在無鹽條件下找出短時間內得到高水解率產物的條件。由實驗結果得知，醬油醪之最適水解溫度為45 oC，於此溫度下水解9小時可得水解率為42.6 %之水解產物。利用本研究之方法，在無鹽條件下，短時間可得到高水解率的無鹽醬油醪水解物，未來可提供無鹽及低鹽醬油之開發，亦可縮短醬油所需之釀造時間。本研究同時探討嫌氣發酵所生產之醬油醪水解液對血管收縮素轉化酶(Angiotensin converting enzyme, ACE)抑制能力之經時變化，結果發現以45 oC水解醬油醪9小時為最佳，ACE抑制能力可達55.6 %；然就實際生產具有血管收縮素轉化酶抑制能力之醬油醪水解液產品而言，建議以50 oC較適合，於此溫度下水解6至12小時，其血管收縮素轉化酶抑制能力皆在50 %左右，較有利於控制產品之品質。 3. 利用食品級酵素水解大豆蛋白製備胜肽及胺基酸產品 高血壓以及心血管疾病一直以來都是十大死亡原因之一，而過去研究指出，若能有效抑制血管收縮素轉化酶之活性將可以有效降低血壓，進一步預防心血管疾病的發生。許多研究指出，蛋白質水解所產生之胜肽容易被人體所吸收，因而具有高度營養價值，並且同時具有抑制血管收縮素轉化酶的效果。本研究利用Bromelain、Flavourzyme、Neutrase及Papain等四種食品級蛋白酶水解大豆蛋白，探討其水解率與血管收縮素轉化酶抑制能力之相關性，期望能開發高血管收縮素轉化酶抑制能力之產品。結果發現，在所測試之四種食品級酵素中，以Flavourzyme對大豆蛋白之水解效果最佳，經過10小時即可達水解率45.3 %。由利用不同酵素進行大豆蛋白水解之血管收縮素轉化酶抑制能力之經時變化可知，以Flavourzyme水解大豆蛋白6小時為最佳，可達58.2 %，初步利用HP-20進行純化，可得ACE之IC50為0.24 % 的區分，較原水解液ACE之IC50 (1.44 %) 低了6倍。利用此酵素水解2至10小時，其水解產物之血管收縮素轉化酶抑制能力皆超過50 %。

Abstract This thesis includes three parts, 1) Utilization of recovered shoyu mash residue, 2) Studies on the hydrolysis of soy sauce koji, 3) Studies on the hydrolysis of soy protein. 1. Utilization of recovered shoyu mash residue. The shoyu mash residue (or referred as soy sauce cake) is the main by-product during soy sauce manufacturing. It is mainly used as an ingredient for preparing feeds. Although shoyu mash residue has been used as a digestible protein, it is incinerated due to the declining livestock industry. A shoyu mash residue contains relatively high amount of salt; therefore, incineration results in corrosion of the furnace and environmental problems. The desalted shoyu mash residue has the excellent physical properties for a good dietary fiber. The purpose of this research is to produce good dietary fiber products from the recovered shoyu mash residue and to increase the yield of soy sauce product. Desalted shoyu mash residue fiber was prepared and their composition and physical properties were measured. In the experiments, the aqueous shoyu mash residue infusion was recycled as the saline water for preparing next batch soy sauce and measurements were carried out. The results indicate that the degree of the hydrolysis is 59.3 % and is higher than the control one (56.7 %) about 2.6 %. The total nitrogen utilization rate is 83.6 % and is higher than the control one (79.7 %) about 4 %. This demonstrates that the waste water from washing the shoyu mash residue can be recovered and reused and thereby reduce the cost of salt and increase the productivity of soy sauce. 2. Studies on the hydrolysis of soy sauce koji. The production of soy sauce is time-consuming. To shorten the time needed for its production the rate of soy sauce koji hydrolysis must be increased. In addition, the salt-free and low-salt soy sauce products are also required as health foods by the consumers. The aim of this part of study is to develop an efficient method for the products. The changes of protein hydrolysis rates during the anaerobic fermentation of the koji were studied. The angiotensin converting enzyme inhibition activities of the peptides of various hydrolysis rates were analyzed. The results indicate that the best temperature for soy sauce koji hydrolysis under anaerobic fermentation is 45 oC. Under this temperature, a hydrolysate of 42.6 % degree of hydrolysis with 9 hours hydrolysis can be achieved. The results of angiotensin converting enzyme test show that hydrolysis for 9 hours at 45 oC can reach a 55.6 % inhibition. However, for a better quality control, condition at 50 oC with 6-12 hours hydrolysis is suggested.

3. Studies on the hydrolysis of soy protein. Recently, peptides have elicited great interest for their multiple bio-functionalities. Among them, especially the peptides made from soy protein are the most popular subjects. The purpose of this research is to employ the koji proteases to produce the peptides of desirable degree of hydrolysis. Four kinds of food grade proteases (Bromelain, Flavourzyme, Neutrase and Papain) were used to hydrolyze soy protein. The angiotensin converting enzyme inhibition activities of the peptides of various hydrolysis rates were analyzed. The results indicate that the best protease for hydrolyze soy protein among the four proteases is Flavourzyme. A hydrolysate of 45.3 % degree of hydrolysis with 10 hours hydrolysis can be achieved. The results of angiotensin converting enzyme test show that by using Flavourzyme hydrolysis for 6 hours 58.2 % inhibition can be attained.