Response surface optimization of dietary fiber extraction process from seabuckthorn fruit residue and evaluation of its application properties
Hippophae rhamnoides Linn., also known as sour thorn or sour willow, has a long history of medicinal and edible use in folk culture. Hippophae rhamnoides leaves have also been included in the list of new resource foods in recent years. China is the country with the richest natural seabuckthorn germplasm resources in the world. It is not only rich in wild seabuckthorn resources, but also the country with the largest area of artificially planted seabuckthorn. It is one of the important tree species in the “Three North” protection forest. According to statistics, as of January 2022, the total seabuckthorn planting area in China is about 31.07 million mu, accounting for more than 90% of the world’s seabuckthorn planting. Seabuckthorn fruit is considered as a good plant resource to prevent and treat cardiovascular disease, diabetes, inflammatory disease, skin disease, gastric ulcer and even cancer because it is rich in vitamins, flavonoids, polyphenols, organic acids, linolein, essential amino acids and other biological active substances.

At present, China’s seabuckthorn industry mainly focuses on beverage processing and extraction of seabuckthorn oil. Among them, Zeng et al. found that microwave pretreatment combined with short-term accelerated solvent extraction can improve the nutritional quality of seabuckthorn oil; Liu et al. optimized the extraction process of seabuckthorn fruit oil; Fu et al. developed fermented seabuckthorn beverages using seabuckthorn pulp as raw material; Li analyzed the current processing status of seabuckthorn fruit wine to promote its development. The residue rate of processed seabuckthorn fruits is about 20%, and most of them are dried and used as animal feed or discarded, directly leading to environmental pollution and waste of land resources. The dietary fiber content in seabuckthorn fruit residue is over 50%. Dietary fiber is known as the “seventh largest nutrient” in the field of nutrition and can be used as an important food filler; It can promote the proliferation of beneficial intestinal bacteria, increase the absorption capacity of the human body, reduce cholesterol and triglycerides in plasma, and help control health effects such as obesity.

Based on this, this study optimized the extraction process of soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) from seabuckthorn fruit residue in the seabuckthorn fruit wine industry, and compared the applicability of different dietary fibers. The aim is to provide theoretical reference for the full utilization of waste resources in the seabuckthorn industry, the production of high value-added dietary fiber products with different usage types, and the extension of the seabuckthorn industry chain.

 

The mechanism of synergistic effect between ultrasound and enzymes is that ultrasound can enhance enzyme activity and further improve dietary fiber yield. In this study, the optimal process was obtained through response surface optimization as follows: adding 5% cellulase, ultrasonic temperature of 60 ℃, ultrasonic power of 120W, and ultrasonic time of 42min. At this time, the SDF yield was (16 ± 1)%, the IDF yield was (73 ± 2)%, and the SDF/IDF ratio was 0.21 ± 0.01. Under the same process conditions, when using ultrasound alone, the SDF yield is (12 ± 4)%, the IDF yield is (65 ± 1)%, and the SDF/IDF ratio is 0.18 ± 0.08; The yield of SDF using cellulose method alone is (11 ± 1)%, the yield of IDF is (67 ± 1)%, and the SDF/IDF ratio is 0.16 ± 0.02. It can be seen that the ultrasound assisted enzymatic method for preparing dietary fiber from seabuckthorn fruit residue has a significant yield advantage and increases the proportion of soluble dietary fiber.
The total dietary fiber of seabuckthorn fruit residue exhibits good application properties, especially in terms of high swelling and oil holding capacity, which are 3.12 ± 0.13mL/g and (4.47 ± 0.41)%, respectively. It also has a good adsorption effect on cholesterol, with cholesterol adsorption almost twice as high as SDF at pH 7.
In summary, utilizing the by-products of sea buckthorn processing, such as fruit residue, can efficiently prepare different types of dietary fiber, improve resource utilization, reduce industry costs, and obtain high value-added products. This has certain economic value and social significance for further promoting the development of the sea buckthorn industry.