What Is the Use of Blueberry Extract Anthocyanin in Food?

Blueberries are the common name for plants of the Vaccinium genus (Vaccinium spp) of the Ericaceae family with blue fruit. In May 2023, the National Health Commission issued an announcement on 14 “three new food” products, including blueberry anthocyanins, which attracted much attention from the food industry. With the accelerated pace of modern life and the widespread use of video terminal equipment, more and more eye diseases have received public attention. Anthocyanins can be absorbed through the oral cavity and pass through the blood-aqueous barrier and blood-retina barrier, removing free radicals in the eyes and promoting microcirculation in the fundus. Based on this, this article will discuss the characteristics of blueberry anthocyanins, with a view to gaining a comprehensive understanding of blueberry anthocyanins and fully utilising them in the food industry.

1. The antioxidant properties of anthocyanins

1.1. Analysis of the composition of blueberries for use in food

Synthetic food antioxidants such as butylated hydroxyanisole, tert-butylhydroquinone, dibutylhydroxytoluene and propyl gallate have all been shown to have certain toxic side effects on the human body after long-term use [1]. Therefore, as a new favorite of the food industry, blueberry anthocyanins are mainly extracted from “Blueme No. 1”. Currently, the purity of new food ingredients containing blueberry anthocyanins is > 40%, and the anthocyanin content is < 1% [2]. Zhang Xiaoxiao et al. [3] used high performance liquid chromatography to determine the anthocyanins in blueberries from different growing regions and found that they contained 15 anthocyanins, which were formed by the combination of five anthocyanins and three sugars. One anthocyanin molecule combines with one sugar molecule to form an anthocyanin molecule.

BEATRIZ et al. [4] studied the effect of the storage environment on blueberry anthocyanins and found that blueberry anthocyanins are more stable under acidic conditions, with the greatest stability at pH = 3.6; they are relatively unstable in alkaline media, and the metabolic half-life of anthocyanins decreases with increasing pH. In addition, light can also accelerate the degradation of anthocyanins, while avoiding light can slow down the degradation rate of anthocyanins. BERGUA et al. [5] found that the degradation of anthocyanins was not significant at 80.0 ℃, and the degradation of anthocyanins was significant (p < 0.05) when it exceeded 80 ℃. Gao Ran et al. [6] found that polyphenol oxidase and peroxidase were completely inactivated at 80 °C, which may be the reason for the better stability of anthocyanins. High-temperature blanching is beneficial to the retention and recovery of anthocyanins.

Many food manufacturers have tried to optimize food processing technology using various extraction and preparation methods to obtain anthocyanins with higher stability. For example, many current food processing technologies combine anthocyanins with semi-preparative blueberry pectin, which not only improves the in vitro stability of anthocyanins, but also increases the amount of anthocyanins transported to the colon (gut microbiota containing metabolizable anthocyanins). Liu Xiaofei et al. [7] combined chondroitin sulfate nanocomplexes with K-carrageenan to form a hydrogel system, and used hydrogel embedding to enhance the stability of anthocyanins. Gao Ran et al. [6] found that adding α- or β-casein to a blueberry anthocyanin solution can enhance the stability of blueberry anthocyanins in foods. If anthocyanin-containing foods are consumed with protein during heating, the degradation trend of anthocyanins can be alleviated. This article organizes the data reported by the National Health Commission in the first half of 2023 and summarizes the scope of application of blueberry anthocyanins in food, as shown in Table 1.

1.2 The antioxidant principle of blueberry anthocyanins

At present, with the development of new resource foods, raw fruit materials represented by “Blueberry No. 1” have been widely used in food processing. At present, blueberry anthocyanins are affected by various factors and are mostly found in canned, jammed, dried, and other single forms on the market. However, as the characteristics of blueberry anthocyanins are studied by more and more scholars, new resource foods similar to blueberry anthocyanins are also valued by many in the food industry, and attempts are being made to extract natural active substances from plants for use in food processing. It can be seen that plant-based novel food ingredients replacing synthetic antioxidants will become an inevitable development trend.

The antioxidant effect of blueberry anthocyanins is mainly achieved by scavenging free radicals, increasing the activity of antioxidant enzymes, inhibiting the body's production of free radicals of the oxidase (NADPH oxidase, lipoxygenase, etc.) and inhibiting lipid peroxidation, etc., which is closely related to the structure of anthocyanins [8]. In addition, some scholars have found that the antioxidant properties of anthocyanins are related to the benzene ring. Although the o-dihydroxy group on the benzene ring can form a stable conjugated quinone radical with free radicals, thereby reducing the internal energy of the anthocyanin molecule and producing hydrogen bonds, which in turn enhance the stability of the free radicals. However, the meta and para positions of the dihydroxy group cannot react with the free radical, and the position of the hydroxyl group on the benzene ring also affects the strength of the free radical scavenging. The ortho dihydroxy group at the C3 and C4 positions has the best antioxidant properties [9].

2. The properties of anthocyanins that protect eyesight

2.1. Overview of eye health

Eye strain is a subjective feeling of eye weakness or fatigue, commonly found in adults, and can be caused by a variety of factors, such as uncorrected refractive errors, unbalanced extraocular muscles, accommodation disorders and improper lighting. In recent years, with the popularity of smartphones, eye strain has become more and more common among children, reaching 19.7% [10]. Therefore, the introduction of nutrients that protect vision in foods plays an important role in protecting eye health. Studies have found that there seems to be a positive correlation between the consumption of omega-3 fatty acids, lutein and zeaxanthin and having healthy eyesight. People whose diet is rich in lutein and zeaxanthin also have a lower risk of age-related macular degeneration, cataract extraction and diabetic retinopathy [11].

2.2 The protective effect of anthocyanins on eyesight

After being absorbed orally, anthocyanins circulate in the liver-gut cycle, pass through the blood-brain barrier, the blood-eye barrier, and cross the blood-aqueous humor barrier and the blood-retina barrier, accumulating in these eye tissues. This indicates that the organs of the digestive tract have an anthocyanin metabolic pathway that combines methylation and glucuronidation enzymatic conversion. Xiao et al. [12] concluded in a rat experiment that anthocyanin 3-glucoside is absorbed in the plasma in the form of glucuronide conjugates and methylation, and thus concluded that orally administered anthocyanins have the potential to be used as a pharmaceutical treatment for ophthalmological diseases (myopia and glaucoma). Zhao Jing et al. [13] showed that orally administered anthocyanins can prevent the refractory conversion of myopia caused by working at visual display terminals. Chen Daoguo et al. [14] found that anthocyanin-3-glucoside and anthocyanin-3-rutinoside in anthocyanins act on the frog retina and improve the regeneration of rhodopsin in retinal tissue. This shows that exploring the vision-protecting properties of blueberry anthocyanins and applying them in food processing will enrich the nutritional composition of foods.

3. Quality analysis of blueberry anthocyanins in food

The National Health Commission states that new food ingredients are not allowed to be added to ordinary foods without being analysed for safety before being approved. However, as a plant extract from blueberries, blueberry anthocyanins have been certified by the National Health Commission and can currently be used in eight types of food, including milk and dairy products, beverages, and jelly. Although blueberry anthocyanins have already been used in single-flavor foods such as bread, biscuits, French fries, tea drinks, and gummies, they are still in the exploratory stage in the dairy product sector. Therefore, this article uses the application of blueberry anthocyanins in related foods as an example to analyze their quality.

3.1 Taste and flavor

At present, many manufacturers in the market have reported that the application of blueberry anthocyanins in dairy products causes a rancid odor. The reason for this may be that when blueberry anthocyanins are incorporated into dairy products, the droplets are large, and the contact area with microorganisms is large, which can easily cause microorganisms to grow. Microorganisms promote the breakdown of fat, which produces an unpleasant smell. A new type of dairy product containing blueberry anthocyanins has also appeared on the market. Many consumers report that it has a rich taste and a long aftertaste. Analysis shows that high-quality blueberry anthocyanins melt quickly in the mouth because the malvidin-3-glucoside in them produces a cooling sensation [15]. The taste buds on the tongue can perceive the flavor of the blueberry anthocyanins, and the fats in blueberry anthocyanin-containing dairy products will dissolve esters during consumption, further enhancing the taste and flavor of the blueberry anthocyanins.

3.2 Viscosity

Currently, some businesses on the market add blueberry anthocyanins to milk tea, and this artificially prepared tea with blueberry anthocyanins can have a viscous mouthfeel. The reason for this is that in the preparation process, the shop uses a lot of organic solvents in the process of extracting the blueberry anthocyanins, or because a large amount of blueberry anthocyanins is added to the milk tea, which also gives diners an unpleasant taste. In the process of preparing blueberry anthocyanins with tea, high temperatures should be avoided as much as possible, and the amount of fat and organic solvents in the water should be reduced.

3.3 Spreadability

3.3.1 Hardness

The hardness not only affects the eating experience of blueberry anthocyanin-containing fruit puree, but is also a key indicator for evaluating the quality of blueberry anthocyanin-containing fruit puree. Samples with excessive hardness have an uneven structure and crystals that do not adhere to each other, resulting in a brittle sample that is not easy to spread and has increased whipping. Samples with low hardness cannot retain their shape and cannot retain the gas that has been mixed in, and have a high whipping degree. Although the hardness of some blueberry anthocyanin fruit pastes is too high, many manufacturers have made improvements in areas such as the high melting point of the oil phase, the conversion of the crystal form, and the control of the cooling time, so that blueberry anthocyanin fruit pastes can be evenly spread on biscuits.

3.3.2 Crystallization rate

A slow crystallization rate results in a softer blueberry anthocyanin chocolate product. To solve this problem, many manufacturers control the crystallization rate of blueberry anthocyanin chocolate during the production process to control the hardness of the product. In addition, many manufacturers have also found that the changes in the crystal form and the crystal network structure of blueberry anthocyanin chocolate products during the production and storage of blueberry anthocyanin chocolate are the main factors causing changes in its toughness. At present, in order to further improve the softening and crystallization problems of blueberry anthocyanin chocolate, many research teams have carried out systematic research from the aspects of tempering temperature, crystallization temperature, and working temperature, and have made phased achievements by improving the processes of sand return, oil release, and chocolate frosting.

3.3.3 Blueberry anthocyanin milk shake is too soft

In order to comply with the new food ingredient standards of the Health Commission's 2023 specifications (blueberry anthocyanins must meet a purity of >40% in food additives), Zhang Wei et al. [16] achieved a research result of purifying blueberry anthocyanins by more than 70%, which far exceeds the European Pharmacopoeia's purity standard of 36%. At present, many businesses have begun to use blueberry anthocyanins in milk shakes, enriching the taste of the product while researching the nutritional composition of anthocyanins in terms of sweetness, thickness, and calorie intake. At present, the more common preparation method on the market is to heat the raw milk to 50-60°C, add a stabilizer, and then add natural anthocyanins (the base material accounts for 0.1%-0.5% by weight). After stirring for 15-30 minutes, the prepared liquid is obtained. If you want to increase the sweetness, you can add an additional 6% to 16% sucrose to enrich the taste of the blueberry anthocyanin milk shake.

4 Conclusion

Anthocyanins are extremely unstable and easily degrade during the extraction process. The extract is mixed with a large number of impurities, which limits the industrial development of anthocyanins. Therefore, the research of low-consumption and efficient extraction and purification technology has become an ongoing goal. However, at this stage, not all water-soluble antioxidants can improve the antioxidant stability of blueberry anthocyanins. Therefore, in order to further enhance the biological activity of anthocyanins in foods, methods for extracting anthocyanins include solvent extraction, enzyme-assisted extraction, ultrasound-assisted extraction, microwave-assisted extraction, etc.

Natural extracts represented by blueberry anthocyanins have unique advantages in terms of cost and antioxidant function. However, due to product regulations, natural extract ingredients may face certain restrictions in specific product applications, and a series of comprehensive considerations, such as toxicity and safety, are required. Further research is needed on the advantages of its antioxidant properties and eye protection, while minimizing any discomfort in terms of flavor and texture. The food processing process must be continuously optimized so that China's anthocyanin food production and processing industries can demonstrate economies of scale while ensuring consistent quality.

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