電解水之製備及對綠竹筍減少總生菌數及貯藏壽命之影響

Abstract

綠竹筍(Bambusa oldhami Munro) 為綠竹未成熟之幼嫩芽體，抽長後即為竹。綠竹筍生長於土中，採收時會沾附大量泥土以及微生物；另一方面，綠竹筍採收時，會產生大面積之切口，切口表面迅速褐化及纖維化及受微生物影響導致竹筍劣變及貯藏壽命縮短。電解水已應用於農業、牙科、醫藥以及食品工業各領域中，且在諸多研究中，皆顯示電解水可用於減少截切蔬菜之微生物數目。本研究旨在瞭解自製無隔膜電解水之特性，並探討電解水應用於減少綠竹筍切口之微生物，以及其對綠竹筍貯藏壽命之影響。研究結果指出，以氯化鉀以及氯化鈉做為電解質，其自由氯濃度以及pH值皆會與濃度呈現線性關係，但氯化鈣之鈣離子則會在陰極板表面沉積，導致電解效率降低，自由氯濃度不會隨濃度上升而改變。以氯化鉀溶液製備電解水，於低溫 (3.5℃)時電解效率會降低，導致自由氯濃度下降。綠竹筍切口表面含有大量生菌數，不易以清洗去除。以常溫電解0.3 M氯化鉀之電解水在低溫 (3.5℃) 中60分鐘，可顯著性降低綠竹筍表面切口生菌數。電解水與次氯酸鈉水溶液以及二氧化氯 (Oxonet)水溶液比較，電解水處理可使總生菌數顯著性下降。將綠竹筍以電解水以及二氧化氯水溶液處理後裝入0.15 mm微孔PE袋中，並放入3℃冷藏，結果顯示，在第10天時，對照組以及二氧化氯水溶液處理，已出現明顯褐化徵狀：電解水處理組到第15天時切口表面才出現明顯褐化徵狀。結果顯示不同處理在綠竹筍貯藏10天後之官能品評與對照組評分相似，表示電解水對於綠竹筍整體口感並無顯著性之影響。

Bamboo shoots (Bambusa oldhami Munro) are immature body of bamboo. They grow up and become the bamboos. Since bamboo shoots are grown in the soil, harvesting of bamboo shoots always result in contamination with microorganisms and dint. In addition, harvesting of bamboo shoots creates a large incision and the incision surface turns brown and hard quickly. The storage life of the bamboo shoots is very shoot due to microorganism caused deterioration. Electrolyzed water (EW) is already widely used in agriculture, dentistry, pharmaceutical and food industries. Many studies had indicated that EW can also be used in fresh-cut vegetables to reduce microorganisms. The purposes of this study were to investigate suitable conditions in generating membrane-less EW (LS-MLEW) and to study EW on the reduction of the total plate count in bamboo shoots as well as on the impact of their shelf-life while applied EW to the bamboo shoots. In this study, potassium chloride, sodium chloride and calcium chloride were used as electrolytes of EW. There were good linear relationships between electrolyte concentration and free available chlorine (FAC) as well as pH value in both potassium chlorides and sodium chlorides solutions. Calcium ions of calcium chloride were deposited on the surface of the cathode plate, which resulted in reducing the efficiency of electrolysis. However, FAC did not change with concentration in calcium chloride solution, this probably due to the deposition Ca++ on the surface of the cathode. At low temperature (3.5℃), the efficiency of electrolysis decreased and the FAC of the EW of potassium chloride also decreased accordingly. Bamboo shoots incision surface contains large number of microorganisms which are difficult to be removed by washing. EW prepared by the electrolysis of 0.3 M potassium chloride at room temperature was used for bamboo shoot treatment. When the bamboo shoots were soaked in EW at low temperature (3.5℃) for 60 minutes, the standard plate counts in the incision surface of bamboo shoots decreased significantly. Comparing with soaking in the common bleach solution (NaOCl) or Oxonet solution (ClO2), soaking in EW significantly decreased the standard plate counts in the incision surface of bamboo shoots. Bamboo shoots were stored in sealed PE bags with a micropore 0.15mm at 3℃ after treated with EW or Oxonet. Results showed that the control group and the aqueous Oxonet, demonstrated significant browning symptoms after10 days in the refrigerator and the EW treatment turned browning after 15 days. Sensory evaluation of the bamboo shoots after 10 days showed no difference among treatments indicating there were no significant differences in the overall taste among treated or un-treated bamboo shoots.