半乾性園產加工食品之試製及其耐菌性之探討

Preparation of Intermediate Moisture Horticultural Foods and Their Stability to Molds

水份活性不但影響生物之生長，且與食品內許多化學反應有密切的關係，因此以控制水份活性及水分含量，製造而成半乾性食品，正逐漸地在發展。本論文用園產物之胡蘿蔔、香蕉及鳳梨為材料，以浸潰法試製半乾性食品，達到預期之水份活性值。同時就所製產品輕接種後觀察其對微生物之穩定性。茲將實驗結果摘錄如下：1.在所選用之三種添加劑中，普通甘油之水份活性可低至0.2，而飽和之蔗糖、食鹽溶液其水份活性分別為0.85、0.75。若以甘油之各濃度，配合蔗糖、食鹽的不同濃度，則對降低水份活性具有相乘效果。2.以胡蘿蔔、香蕉、鳳梨為原料，製成不同水份活性之半乾性食品，其中胡蘿蔔與鳳梨無論在色澤、香氣上均良好，惟香蕉雖收量較大但有褐變、香氣喪失及組織軟體之缺點。3.上述半乾性食品，經接種黴菌後，於25℃，90% R.H.下觀察49天，顯示水分活性0.8並非安全。尤其香蕉於水份活性0.75時，仍無法抑制黴菌之生長。因此園產物之半乾性食品，其Aw必須控制於0.75以下，才可保證其對一般微生物之安全性。

Carrots, bananas and pineapples were employed as raw materials and glycerol, sucrose and sodium chloride were used as additives, then intermediate moisture foods (IMF) were prepared by soak infusion method. These products have inoculated with Aspergillus niger and Penicillium chrysogenum to observe their stability. 1. Among three additives, commercial glycerol at 25℃ has an water activity as low as 0.2, while the saturated solution of sucrose and sodium chloride have indicated 0.85 and 0.75, respectively. Using glycerol as base, mixed with various concentrations of sucrose or sodium chloride have an enhance effect on decreasing Aw of the mixture. 2. Both color and flavor of equilibrated carrots and pineapples are good. The yield of equilibrated banana product was higher but it had defects in browning, off-flavor and softing in texture. 3. After inoculated with molds, the equilibrated products have been storaged at 25℃ and 90% R. H. for 49 days, those products are not stable at Aw=0.8. The banana sample, even it had an Aw value at 0.75 could not inhibit the growth of molds. A suggestion on the intermediate moisture horticultural foods must be kept Aw under 0.75 as shown by this investigation.