Formulations based on polysaccharides and proteins have proved
their excellent selective permeability to O2 and CO2. However, because
of their hydrophilic nature they exhibit poor moisture barrier properties,
which can be improved by adding hydrophobicmaterials such as natural
waxes, acetylated monoglycerides and surfactants through emulsion or
lamination technology. That is why edible films usually are heterogeneous
in nature.
Literature data indicate that O2, CO2 and water vapor permeability
of edible coatings are lower than the conventional plastic films. Starch
films ability for food protection is by controlling and reducing oxygen
transport, thus extending the shelf life of the food.
However, the incorporation of antimicrobial agents to starch films increases
O2 gas permeability thus incorporation of potassium sorbate to
sweet potato starch films, led to higher oxygen permeability [52]. The
mass transfer of oxygen in a semi-crystalline polymer is primarily a function
of the amorphous phase, because the crystalline phase is usually
assumed to be impermeable. Fama et al. [53,55] showed that the incorporation
of potassium sorbate decreased the crystallinity of tapioca-starch
edible films causing an increase in oxygen permeation (OP) of the starch
films. The incorporation of potassium sorbate weakened inter-molecular
forces between adjacent starch polymeric chains, facilitated chain mobility
and increased the free volume between starch molecules, which
promoted oxygen permeability [132].However, a better oxygen transportation
barrier property was obtained with the starch films when chitosan
was incorporated. With 15% of chitosan, sweet potato starch film had a
significantly lower OP (1.94±0.95×10−6 cm3×m/(m2×d×kPa)) than
that of the control starch film. Chitosan could forminter-molecular hydrogen
bonds with starch, which limited the inter-molecular chain mobility
and decreased its free volume, contributing to the decrease of OP. Moreover,
Xu et al. [31] reported that chitosan film possessed low permeability
to oxygen.
Mathew and Abraham [43] determined the water vapor transmission
(WVT) of films gravimetrically. The films were fixed on to the
circular opening of permeation cell-containing anhydrous calcium
chloride (0% RH) using melted paraffin. The cups were then weighed
and placed at 92% relative humidity and 37 °C in a humidity chamber.
The cups were weighed at 1-h intervals until the change in weight became
constant. The water vapor transferred through the films at different
time intervals were determined from the weight gain of the
cups. Changes in the weight of the permeation cell were recorded
and plotted as a function of time. The slope of each line was calculated
by linear regression and WVT rate was calculated from the slope of
the straight line (g/h) divided by the transfer area (m2).
Oxidized ferulic acid incorporated films were found to significantly
decrease the WVT compared to the control blend films, probably due
มีพิสูจน์สูตร polysaccharides และโปรตีนการ permeability แห่งใช้ O2 และ CO2 อย่างไรก็ตาม เนื่องจากธรรมชาติของ hydrophilic จะแสดงคุณสมบัติของอุปสรรคความชื้นต่ำซึ่งสามารถปรับปรุงได้ โดยการเพิ่ม hydrophobicmaterials เช่นธรรมชาติไข acetylated monoglycerides และ surfactants โดยอิมัลชัน หรือเทคโนโลยีเคลือบ นั่นคือเหตุผลที่ฟิล์มกินมักจะแตกต่างกันในธรรมชาติข้อมูลประกอบการแสดงที่ permeability O2, CO2 และไอน้ำของกินเคลือบได้ต่ำกว่าฟิล์มพลาสติกทั่วไป แป้งฟิล์มความสามารถป้องกันอาหารเป็นการควบคุม และลดออกซิเจนขนส่ง จึง ขยายอายุการเก็บรักษาอาหารอย่างไรก็ตาม ในการประสานตัวแทนแป้งฟิล์มจุลินทรีย์เพิ่มขึ้นPermeability ของก๊าซ O2 จึงประสาน sorbate โพแทสเซียมเพื่อฟิล์มแป้งมันเทศ นำไป permeability ออกซิเจนสูง [52] ที่โอนมวลของออกซิเจนในพอลิเมอร์กึ่งผลึกเป็นฟังก์ชันหลักของไปเฟส เนื่องจากเฟสผลึกมักจะสมมติให้การซึมผ่านของ Al. ร้อยเอ็ด Fama [53,55] พบว่าจดทะเบียนของโพแทสเซียม sorbate crystallinity ของแป้งมันสำปะหลังที่ลดลงฟิล์มกินก่อให้เกิดการเพิ่มขึ้นในการซึมผ่านของออกซิเจน (OP) ของแป้งฟิล์ม จดทะเบียนของโพแทสเซียม sorbate ระหว่างโมเลกุลลดลงกองกำลังระหว่างแป้งติดชนิดโซ่ โซ่สภาพปานกลางคล่องตัวและเพิ่มปริมาณฟรีระหว่างโมเลกุลแป้ง ซึ่งpromoted oxygen permeability [132].However, a better oxygen transportationbarrier property was obtained with the starch films when chitosanwas incorporated. With 15% of chitosan, sweet potato starch film had asignificantly lower OP (1.94±0.95×10−6 cm3×m/(m2×d×kPa)) thanthat of the control starch film. Chitosan could forminter-molecular hydrogenbonds with starch, which limited the inter-molecular chain mobilityand decreased its free volume, contributing to the decrease of OP. Moreover,Xu et al. [31] reported that chitosan film possessed low permeabilityto oxygen.Mathew and Abraham [43] determined the water vapor transmission(WVT) of films gravimetrically. The films were fixed on to thecircular opening of permeation cell-containing anhydrous calciumchloride (0% RH) using melted paraffin. The cups were then weighedand placed at 92% relative humidity and 37 °C in a humidity chamber.The cups were weighed at 1-h intervals until the change in weight becameconstant. The water vapor transferred through the films at differenttime intervals were determined from the weight gain of thecups. Changes in the weight of the permeation cell were recordedand plotted as a function of time. The slope of each line was calculatedby linear regression and WVT rate was calculated from the slope ofthe straight line (g/h) divided by the transfer area (m2).Oxidized ferulic acid incorporated films were found to significantlydecrease the WVT compared to the control blend films, probably due
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