Antioxidant levels and activity significantly increase during the processing and digestion of Japanese apricots pickled with salted red perilla leaves, according to new research.
Shiso-zuke umeboshi, a traditional Japanese apricot pickle that utilizes salted red perilla leaves, is recognized for its numerous health benefits due to its rich phenolic compound content. These compounds possess antioxidant, anti-inflammatory, and antimicrobial properties, making Shiso-zuke umeboshi valued for both culinary and medicinal purposes. A recent study investigated both the quantitative and qualitative shifts in phenolic profiles and antioxidant potency of Shiso-zuke umeboshi throughout processing and simulated digestion. The findings showed a notable increase in phenolic content during processing, with antioxidant levels and activity rising steadily across different digestive phases, reinforcing the health advantages associated with this preservation technique.
The varied biochemical makeup of Japanese apricot fruits accounts for their extensive effects on human health. Elevated amounts of vital phenolic compounds and hydroxycinnamic acids contribute to several health benefits, including anti-inflammatory, antioxidant, and antimicrobial effects.
A recent investigation published in Food Research International on July 19, 2024, conducted by Prof. Yukiharu Ogawa and Jutalak Suwannachot from Chiba University, quantitatively assessed the changes in phenolic compounds and antioxidant activity in Shiso-zuke umeboshi production. This study also replicated the digestive process to analyze the release of these compounds and their antioxidant effects.
“While some benefits have been noted in the pickling process with red perilla, the existing data is still quite limited. Recently, there has been a push to develop functional foods that not only offer health benefits but also provide essential nutrients beyond traditional micronutrients. However, the specific effects of apricot pickles with red perilla (Shiso-zuke umeboshi) remain unclear, which is why we conducted this research,” explains Prof. Ogawa.
In this study, three techniques were used for producing perilla-pickled apricots: simple salt pickling (SP), 30 days of pickling with salted perilla leaves (30-PP), and 60 days of pickling with salted perilla leaves (PP). The samples underwent ultrasonic treatment, and the resulting supernatants were extracted through centrifugation to quantify both free and esterified phenolics in the aqueous phase. The remaining solids were analyzed to evaluate insoluble-bound phenolics in the organic phase.
All three phenolic fractions were analyzed using liquid chromatography-mass spectrometry (HPLC-PDA-QDa), focusing on their peak areas at 280 and 320 nm wavelengths.
To assess total phenolic content (TPC), researchers employed the Folin-Ciocalteu reagent test, while total flavonoid content (TFC) was obtained using a 96-well microplate method in conjunction with an aluminum chloride (AlCl3) colorimetric assay. Antioxidant activity was then evaluated at 740 nm, with results expressed in millimoles (mmol).
The research team simulated the gastrointestinal digestion of apricot pickles by adjusting the sample’s pH to mimic the varying conditions throughout the digestive tract. They introduced digestive enzymes and filtered the digested fractions to identify components and assess their antioxidant activity.
The HPLC chromatogram identified the main phenolic compounds as rosmarinic, caffeic, p-coumaric, and ferulic acids. A comparative analysis revealed an increase in bioactive compound concentration from the 30-day pickling process (30-PP) to the final product (PP). Among the phenolics, rosmarinic acid (RA) was the most abundant across all samples. Ferulic acid was found in lower concentrations, notably in esterified fractions, which also exhibited greater quantities of caffeic and p-coumaric acids. The lesser concentration of ferulic acid is likely due to its lower solubility in water.
During the simulated in vitro digestion, researchers compared the effects of simple salt pickling (SP) versus salt pickling with perilla (PP) at various stages: before digestion (G0), one hour post-gastric digestion (G60), at the transition to intestinal digestion after 60 minutes (G60), and two hours into small intestinal digestion (I120).
The highest release of bioactive compounds was noted at G0, while the lowest was found at G60. However, a significant surge in bioactive compound release occurred between G60 and I120. At I120, both SP and PP exhibited the highest levels of TPC and TFC, likely due to the impact of pH conditions and intestinal enzymes that enhanced TPC and TFC concentrations.
In terms of antioxidant activity, PP displayed greater potential throughout the simulated gastrointestinal digestion compared to SP, showing a consistent upward trend as opposed to SP’s steadiness. Overall, the acidic conditions during pickling appear to promote better availability of RA and other compounds from perilla.
“The health advantages of Japanese apricot pickles largely stem from the antioxidant compounds found in red perilla, which serves as both a natural food dye and a beneficial ingredient,” concludes lead researcher Jutalak Suwannachot.
