添加混合磷酸鹽羊乳以試驗型管式UHT殺菌機進行滅菌處理之可行性評估

台灣夏季常有剩餘羊乳，需進行滅菌處理提升其保存期限。羊乳游離鈣含量高於牛乳，使其熱安定性較牛乳差，而添加磷酸鹽於羊乳中可降低游離鈣含量，並提升酒精安定性及熱安定性。本研究主要目的為於生羊乳添加混合磷酸鈉（blend of sodium phosphate, Na）提升安定性後，以小型試驗型管式UHT殺菌機滅菌，探討未來生產常溫保存UHT滅菌羊乳之可行性，並了解儲存期間品質、安定性及感官品評之變化，以解決台灣夏季剩餘羊乳問題。本研究之阿爾拜因（Alpine）生羊乳來源為屏東縣長治鄉某阿爾拜因乳羊場。試驗一為探討阿爾拜因生羊乳添加0.05至0.08 ％之混合磷酸鈉（Na）後，以高壓滅菌釜（autoclave）模擬超高溫瞬間滅菌（ultra-high temperature, UHT, 135℃ 15 sec）條件處理，對其理化性質及安定性之影響，探討最安定混合磷酸鈉（Na）添加量，以利後續以試驗型管式UHT殺菌機加工進行。試驗二為探討阿爾拜因生羊乳添加0.08 ％之混合磷酸鈉（Na）後，分別以UHT（135℃, 15 sec）、autoclave（121℃, 15 min）及以超高壓（high pressure processing, HPP）於 25℃ 400 MPa分別加壓 5及25分鐘，探討長期儲存於冷藏及常溫環境中對滅菌羊乳之品質、安定性及感官品評之影響。試驗一結果顯示，以添加0.08 ％於阿爾拜因生羊乳為最適合進行試驗用管式UHT殺菌機。試驗二結果顯示，以UHT及autoclave可到滅菌程度，而HPP仍不足以達到滅菌程度；UHT處理組於不同溫度儲存56天，其滴定酸度（TA）及色澤皆較autoclave變化程度小；酒精安定性、沈澱物比例及擴散穩定分析指數（Turbiscan Stability Index, TSI）結果顯示，於冷藏及常溫儲存期間UHT及autoclave處理組安定性良好；差異性品評結果顯示以UHT處理組整體評分與市售羊乳最為相近且羊羶味較市售羊乳低。綜合上述，於生羊乳添加0.08 ％混合磷酸鈉（Na）以試驗型管式UHT殺菌機滅菌，從品質、安定性分析及感官品評顯示以UHT滅菌羊乳於儲存期間其品質及安定性穩定，且感官品評與鮮羊乳相近，評估未來可以於生羊乳添加0.08 ％混合磷酸鈉（Na）進行UHT（135℃, 15 sec）之條件為依據，發展常溫保存UHT滅菌羊乳，解決台灣夏季剩餘羊乳問題。

關鍵字

試驗型管式UHT殺菌機；混合磷酸鈉；滅菌羊乳

並列摘要

Taiwan usually has excess goat milk in summer. Goat milk can be steri-lized to enhance shelf life. Low content of αS1- casein and high calcium ion content of goat milk causes goat milk to have poor thermal stability. Adding phosphate can improve thermal stability of goat milk. The purpose of this study was to evaluate of producing sterilized phosphate salt-added goat milk with a lab-scale tubular UHT pilot plant.Experiment 1 investigated the effect of adding 0.05- 0.08 % blend of sodium phosphate (Na; Na0.05- Na0.08) after autoclave-imitating UHT (135℃, 15 sec) sterilization on the quality and stability of Alpine raw goat milk. Experiment 2 investigated the effect of with/without adding 0.08 % blend of sodium phosphate (Na) after ultra-high temperature (UHT, 135℃,15 sec; UNa0.08), autoclave (121℃, 15 min; ANa0.08) and high-pressure processing (HPP, 25℃, 400 MPa, 5 or 25 min; H5, H5Na0.08, H25, H25Na0.08) on the quality and stability of Alpine raw goat milk.Results of experiment 1 showed Na0.08 was the best for experiment 2 in this study. Experiment 2 results showed UHT and autoclave treatments were sterilized, but HPP treatments was not. UNa0.08 goat milk had the minimum TA, color, changes during 4 and 25℃ storage for 56 days. Ethanol stability, sediment content and Turbiscan stability index (TSI) results showed that UNa0.08 had good stability for 56 days. Sensory evaluation results showed that sweet, salty, color and smooth of UNa0.08 were similar to fresh goat milk.To sum up, goat milk with addition of 0.08 % blend of sodium phosphate (Na) sterilized with UHT pilot showed similar quality to fresh goat milk and was stable during cold and room temperature storage. Furthermore, sterilized UHT (135℃, 15 sec) 0.08 % Na-added goat milk has the potential to solve the problem of excess summer goat milk in Taiwan.