The content of anthocyanins in blueberries is influenced by various factors, including variety characteristics, growth environment, cultivation management, maturity, and processing and storage methods. The following are specific influencing factors and principle analysis:

1、 Variety differences (genetic factors)

There are significant differences in anthocyanin content among different blueberry varieties, mainly determined by genes:

High bush blueberries (mainstream artificially cultivated varieties such as "Lanfeng" and "O'Neill"):

The anthocyanin content is moderate (about 200-400 mg/100g), the fruit is large, and the skin color is mostly dark purple.

Low bush blueberries (wild varieties such as the North American "Northern Blueberries"):

The fruit is smaller, the skin color is darker (nearly black), and the anthocyanin content is higher (up to 470 mg/100g), as plants in the wild need to synthesize more antioxidants to resist adversity.

Rabbit eye blueberries:

The anthocyanin content is between high and low clumps, and some varieties (such as "Peak") have higher anthocyanin content in their fruit peels.

2、 Growing environment

1. Light intensity and duration

Impact mechanism:

Light is a key inducing factor for anthocyanin synthesis. Adequate sunlight (especially ultraviolet light) can stimulate the phenylalanine metabolic pathway in leaves and fruits, promoting the synthesis of anthocyanin precursors.

example:

Blueberries grown outdoors have 20% -30% higher anthocyanin content than greenhouse varieties;

The anthocyanin content of blueberry in high altitude areas (such as Yunnan and Xizang) is generally higher than that in low altitude areas due to strong ultraviolet radiation.

2. Temperature (day night temperature difference and accumulated temperature)

Low temperature stress:

Blueberries will initiate a stress response in low temperature environments (such as cold zones and autumn cooling periods), synthesizing more anthocyanins to resist cold and free radical damage. For example, wild blueberries in Northern Europe reach their peak anthocyanin content before winter.

Temperature difference between day and night:

High temperatures during the day promote the accumulation of sugar through photosynthesis, while low temperatures at night inhibit the consumption of respiration and may enhance the activity of anthocyanin synthase. A larger temperature difference (such as in temperate regions) is conducive to the accumulation of anthocyanins.

3. Soil conditions

PH value:

Blueberries prefer acidic soil (pH 4.0-5.5), which can activate the availability of trace elements such as iron and manganese in the soil. These elements are cofactors of anthocyanin synthase. Alkaline soil can lead to poor growth of blueberries and a decrease in anthocyanin content.

Organic matter content:

Soil rich in organic matter, such as humus soil, can provide more comprehensive nutrients, promote root development and fruit metabolism, and indirectly increase anthocyanin content.

4. Moisture and humidity

Moderate drought stress:

Moderate water control during the growth period (non extreme drought) can induce stress responses in plants and promote anthocyanin synthesis. However, long-term water shortage can lead to hindered fruit development and a decrease in fruit content.

High humidity:

Excessive humidity can easily cause diseases such as gray mold, affecting fruit health and potentially leading to reduced anthocyanin synthesis.

3、 Cultivation management measures

1. Fertilization and Nutrients

nitrogenous fertilizer:

Excessive application of nitrogen fertilizer can promote nutrient growth (lush branches and leaves), but inhibit anthocyanin synthesis; Moderate nitrogen fertilizer (combined with phosphorus and potassium fertilizers) can balance growth and metabolism.

Potassium fertilizer:

Potassium can enhance the transportation and accumulation of sugar in fruits, which is a precursor substance for anthocyanin synthesis. Applying potassium fertilizers (such as potassium sulfate) can increase anthocyanin content by 10% -20%.

Trace elements:

Magnesium, boron, zinc and other elements participate in enzymatic reactions, and their deficiency can affect anthocyanin synthesis. For example, magnesium deficiency can lead to leaf chlorosis, indirectly reducing fruit nutrient supply.

2. Pruning and thinning fruits

Reasonable pruning:

Pruning overly dense branches can improve ventilation and transparency, promote fruit exposure to more light, and thus increase anthocyanin synthesis.

Shuguo:

Reducing the yield of fruits per plant and concentrating nutrient supply to preserve fruits can increase the anthocyanin content of individual fruits (similar to the principle of "eugenics").

3. Pesticides and growth regulators

Plant hormones:

Exogenous application of abscisic acid (ABA) or ethylene can simulate ripening signals and initiate anthocyanin synthesis pathways in advance, but may affect the natural flavor of the fruit.

Pesticide residues:

Some insecticides or fungicides may interfere with plant metabolism, and long-term abuse may reduce fruit quality and anthocyanin content.

4、 Maturity level

Immature stage:

The fruit is green or red in color, mainly containing chlorophyll and a small amount of carotenoids, with extremely low anthocyanin content (<50 mg/100g).

Color transition period:

The skin begins to turn purple, chlorophyll degrades, and anthocyanins rapidly accumulate (with a daily increase of 20-50 mg/100g).

Complete maturity period:

The skin is deep purple to black, and the anthocyanin content reaches its peak (such as high bush blueberries, which can reach 300-400 mg/100g).

Overdipe period:

The fruit may experience a slight decrease in anthocyanin content (about 5% -10%) due to enzymatic oxidation or microbial action.

5、 Processing and storage after harvesting

1. Processing method

Fresh fruit: Anthocyanins are most fully preserved (100%).

Frozen storage:

Low temperature (-18 ℃) can inhibit enzyme activity and reduce anthocyanin loss (about 10% -15%), making it suitable for long-term storage.

Hot processed products:

Jam and dried fruits: High temperature (>80 ℃) and prolonged processing can damage the structure of anthocyanins, resulting in a loss of up to 30% -50%;

Dried blueberries: Due to dehydration and concentration, the anthocyanin content per unit weight may increase, but water-soluble anthocyanins may be lost due to sugar stains.

2. Storage conditions

Room temperature storage:

As time goes on, fruit respiration consumes nutrients, and anthocyanin content decreases by about 5% -8% daily (especially in damaged fruits).

Refrigeration (4 ℃):

It can delay metabolism, and after one week of storage, anthocyanin loss is about 10% -15%, which is better than normal temperature environment.

6、 Other factors

Effects of pests and diseases:

When fruits are invaded by gray mold, fruit flies, etc., plants will first activate defense mechanisms (such as synthesizing phytohormones), which may inhibit the normal synthesis of anthocyanins and lead to a decrease in their content.

Altitude and latitude:

Blueberries from high-altitude (such as over 2000 meters) and high latitude (such as Northern Europe and Canada) regions generally have higher anthocyanin content due to strong sunlight and large temperature differences.

Summary: How to obtain blueberries with high anthocyanin content?

Choose the right variety: Priority should be given to low bush blueberries (wild varieties) or dark high bush varieties (such as "Blue Gold" and "Ricka").

Pay attention to the production area: choose high-altitude, temperate or cold zone production areas (such as Yunnan, China, Quebec, Canada).

Maturity assessment: Select fruits with deep purple skin and slightly red around the stem, avoiding green or overly soft fruits.

Fresh consumption or frozen storage: reduce processing steps and maximize nutrient retention.

By comprehensively controlling the above factors, the intake efficiency of anthocyanins in blueberries can be effectively improved, fully exerting their antioxidant and other health benefits.