Effects of Heat and High Pressure Homogenization on Ascorbic Acid in Kiwifruit Juice

Effects of Heat and High Pressure Homogenization on Ascorbic Acid in Kiwifruit Juice Introduction Kiwifruit juice is a popular beverage known for its high vitamin C content, primarily in the form of ascorbic acid. However, during processing, factors such as heat and high pressure homogenization (HPH) can impact the stability and retention of ascorbic acid in the juice. This literature review aims to explore the effects of heat and HPH on ascorbic acid in kiwifruit juice, discussing the mechanisms involved and potential measures to improve its stability. Additionally, two other juice processing techniques will be examined, along with their mechanisms of action, and the implications of this study for consumers and the food industry. Why and How Heat Affects Ascorbic Acid in Kiwifruit Ascorbic acid is a heat-sensitive compound that can undergo degradation at elevated temperatures. Heat can cause the breakdown of ascorbic acid through oxidation reactions, resulting in a loss of its nutritional value. The loss of ascorbic acid during heat processing of kiwifruit juice can be attributed to factors such as prolonged exposure to high temperatures and the pH of the juice. Higher temperatures and lower pH levels accelerate the degradation of ascorbic acid. Differences in Effects between Heat and High Pressure Homogenization on Ascorbic Acid Heat processing involves the application of elevated temperatures to kiwifruit juice, which can lead to the degradation of ascorbic acid. On the other hand, high pressure homogenization involves subjecting the juice to high pressures, which can also impact ascorbic acid content but through different mechanisms. Heat processing primarily leads to oxidative degradation of ascorbic acid, while high pressure homogenization can cause physical disruption of cellular structures, leading to the release of enzymes that accelerate ascorbic acid degradation. Mechanisms for Heat and High Pressure Homogenization Effects Heat processing causes the denaturation of enzymes involved in ascorbic acid degradation, thereby slowing down its degradation rate. However, prolonged exposure to high temperatures can lead to a significant loss of ascorbic acid due to oxidation reactions. High pressure homogenization disrupts cell membranes, releasing enzymes such as ascorbate oxidase that catalyze the breakdown of ascorbic acid. Additionally, the mechanical shearing forces generated during homogenization can contribute to the degradation of ascorbic acid. Measures to Improve Stability during Thermal or HPH Processing Blanched pre-treatment: Briefly exposing kiwifruit before processing to high temperatures can inactivate enzymes responsible for ascorbic acid degradation, thereby improving its stability during subsequent heat or HPH processing. pH adjustment: Modifying the pH of kiwifruit juice can impact the stability of ascorbic acid. Increasing the pH towards alkaline conditions can help preserve higher levels of ascorbic acid during thermal or HPH processing. Two Suitable Juice Processing Techniques and Their Mechanisms Pulsed Electric Field (PEF) Processing: PEF involves subjecting juice to short, intense electric pulses that disrupt cell membranes and inactivate enzymes. The disruption of cell membranes facilitates better extraction of nutrients while reducing enzyme activity that can degrade ascorbic acid. Ultraviolet (UV) Light Processing: UV light treatment exposes juice to specific wavelengths of light that have antimicrobial effects. This reduces microbial load in the juice, minimizing enzymatic activity that can degrade ascorbic acid. Implications for Consumers and the Food Industry For consumers: Understanding the effects of heat and HPH on ascorbic acid in kiwifruit juice highlights the importance of consuming fresh or minimally processed juices to maximize vitamin C intake. For the food industry: This study emphasizes the need for optimized processing techniques that minimize the loss of ascorbic acid during thermal or HPH treatments. Implementing appropriate pre-treatments and adjusting pH levels can help preserve ascorbic acid content in kiwifruit juice, ensuring higher nutritional quality for consumers. In conclusion, heat and HPH can both impact the stability and retention of ascorbic acid in kiwifruit juice. Heat primarily leads to oxidative degradation, while HPH induces enzymatic breakdown through mechanical disruption. Pre-treatments, pH adjustment, and alternative processing techniques like PEF and UV light can be employed to improve the stability of ascorbic acid during thermal or HPH processing. Understanding these effects is crucial for consumers seeking optimal nutrient intake and for the food industry aiming to maintain nutritional quality in processed kiwifruit juice products.    

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