Every year students in our Organic Chemistry class review a journal article and write a blog post about it. This blog post was written by Adam Wiss.
My assignment was to pick a journal article to review and discuss in class. The article had to pertain to some area of organic chemistry. I picked this journal article that deals with fruit juice-milk beverages, because I enjoy learning about nutrition. The experiment was completed by a group in Spain led by Laura Salvia-Trujillo. The article, “Changes in Water-Soluble Vitamins and Antioxidant Capacity of Fruit Juice-Milk Beverages As Affected by High-Intensity Pulsed Electric Fields (HIPEF) or Heat during Chilled Storage,” looks at the components of these beverages after different types of processing and after being stored.
Introduction:
With a rise in obesity and cardiovascular disease, companies have been exploiting the opportunity and promote “the most healthful items on the market.” Therefore, nutritious items are becoming increasingly more accepted. Fruit juices and milk are in this category because of their antioxidant properties. In order to market these products and make them easily accessible, companies must determine how to retain the properties of the natural product. High-intensity pulse electric fields is a suggested method to accomplish this. This study uses HIPEF processing, thermal treatment, and untreated fruit juice-milk beverages to evaluate initial and final values of vitamin C, B vitamins, antioxidant capacity, enzyme activity, and color. HIPEF has been seen to make a substance preserve antioxidant powers. Also, two enzymes, peroxidase (POD) and lipoxygenase (LOX), can be harmful to healthful items that are processed. Optimistically, the goal for HIPEF was to inactivate these detrimental enzymes.
Materials and Methods:
The samples used in this experiment were an orange, mango, kiwi, and pineapple fruits that were purchased at a supermarket in Lleida, Spain. These fruits were cleaned, juiced, then mixed with commercial pasteurized whole (FJ-WM) or skim milk (FJ-SM). As mentioned previously, HIPEF and thermal treatment were used to process the samples. HIPEF is a non-thermal method of stabilizing food products that uses pulses of electricity to inactivate microbes while keeping its nutritional integrity. For the thermally treated method, microorganisms were eradicated by pumping the samples through a stainless steel heat exchanger coil system. Experiments were carried out twice in order to attain a mean value that would be used for ANOVA and significance differences.
Results:
Vitamin C content was retained 99.5 and 97.0% after applying HIPEF. These results have also been observed in other experiments. Furthermore, Vitamin C degradation was slower in the thermally treated samples than HIPEF and untreated. This could be due to lower POD inactivation in HIPEF treated beverages compared to thermal processing. HIPEF processed samples retained 50% Vitamin C content after 21 days; however, thermally processed samples retained it for 28 days. For B vitamins, each method withheld the suggested values reported by the USDA after processing and storage. It was interesting that HIPEF treated and untreated beverages were observed to have significantly higher levels of riboflavin after processing and storage compared to thermally treated beverages. This was not similar to results from other studies. As a result, one can conclude that water-soluble vitamins are more susceptible to heat than HIPEF. The B vitamins remained stable during storage. No significance was found in amount of antioxidants of treated or untreated beverages following processing. However, antioxidant capacity values were significantly correlated with vitamin C content. Furthermore, FJ-WM demonstrated higher antioxidant capacity than skim milk, regardless of treatment. This shows a contribution from lipophilic antioxidants to scavenge radicals in the products. For enzyme activity, while POD activity significantly decreased after HIPEF, it had a minimal effect on LOX activity in either beverage. In the HIPEF processed samples, the type of milk used was relative to the amount of POD inactivated with skim milk being lower. Thermal treatments also significantly decreased POD activity, but they also significantly lowered LOX activity in both milk types. The tests showed that POD activity was irreversible after HIPEF and thermally treated samples. Since levels of LOX significantly increased from the third week of storage in all samples, despite type of milk or treatment, then it’s proven that HIPEF nor heat cause irreversible changes in LOX activity in fruit juice-milk beverages. With respect to color, HIPEF and thermally treated FJ-WM and FJ-SM samples had lighter values after processing and during storage compared to the beverages that were untreated. Hue angle values showed significant decrease no matter what treatment was applied.
Final note:
Overall I thought this experiment was completed well. However, some questions did arise during my research. First, the article did not explain why the fruits (orange, mango, kiwi, and pineapple) were used. I would assume the types of fruit used could make a significant difference in results, especially if the pH is not kept consistent. Furthermore, I’m curious as to how the HIPEF and thermal settings would affect the results, and why they chose these. Another thing that caught my attention was how often the journal article referenced other experimental results. It seemed odd, even though the results were usually similar to what others had discovered, to put all of that information into the article with their results. This made it difficult to distinguish which results belonged to the experiment at hand. Also, I would like to know if beverages with greater concentrations of vitamin C and B vitamins would have a better retention rate after processing and storage.
