Bilberry juice processing

Processing fruit into juice is a popular product option and a way to extend marketing windows and shelf life of the berries. Berries can be frozen after harvesting to reduce the effects of pectin and gelling, as well as to extend utilization beyond the narrow harvest season.

Intact fruits from the frozen berries were thawed. The thawed bilberries then immediately heated to 95 °C for 2 min, and then cooled to 38 °C. Subsequently, the thawed berries were squeezed in a hydraulic juice press.

To improve juice recovery, berries can be treated with elevated temperatures. Heating or blanching the berries before pressing is a common step used in juicing fruits. Cold press extracted juice has a light blue color and delicate flavor, although hot press enzyme treated juice has a deep purple-blue color and stronger flavor.

Juices were pooled and diluted with ultra-pure water at the ratio of 1:1 (v/v). The juices were then cooled down to room temperature in a cold-water bath. The pH and °Brix were subsequently adjusted to 3.5 and 14.0 using sodium hydroxide and sucrose, respectively.
Bilberry juice processing

Phenolic compounds in bilberry juice

Phenolic compounds regulate the various metabolic functions including structure and growth, pigmentation and are resistant to different pathogens in plants.

Plant phenolics are considered to have a key role as defense compounds when environmental stresses, such as high light, low temperatures, pathogen infection, herbivores, and nutrient deficiency, can lead to an increased production of free radicals and other oxidative species in plants.

Bilberry juice are considered one of the richest sources of dietary anthocyanins and antioxidants. Many phenolic compounds have been identified in bilberries and differences in their phenolic profiles have been observed and linked to numerous factors. Anthocyanins represent the most important group in bilberries, contributing to their attractive purple-blue color hues but also defining quality traits.

These polyphenolic components have high-antioxidant content, and are believed to be the key compounds responsible for the many reported health benefits of consuming bilberry juice.

The anthocyanin composition of bilberries is characterized by 15 anthocyanin glycosides in which five antocyanidins (delphinidin, cyanidin, petunidin, peonidin, malvidin) are combined with three types of sugars (galactose, glucose, arabinose).
Phenolic compounds in bilberry juice

Bilberry juice

Bilberries are abundant in polyphenols. Dietary polyphenols have been associated with strategies for prevention and treatment of chronic inflammatory diseases.

Many studies have demonstrated 4 week or longer supplementation of blueberry juice or bilberry extract are able to lower oxidative DNA damage in human. The results showed both juice and fresh fruit of blueberry/bilberry contributed to the protection on peripheral leucocytes in a very short time frame. Asian Food Science Journal 2(1): 1-7, 2018; Article no.AFSJ.41223

Bilberry contains a variety of phenolic compounds, including flavonols (quercetin, catechins), tannins, ellagitannins, and phenolic acids, but anthocyanins make by far the largest contribution to its phytochemical mix.

The flavonol-O-glycosides in fresh bilberry juice and fruit include quercetin-3-rhamnoside (quercitrin), quercetin-3-glucoside (isoquercitrin), quercetin-3-galactoside (hyperoside), and kaempferol-3-glucoside (astragalin).

The following phenolic acids have been identified in fresh bilberry juice and unripe fruit: gallic, protocatechuic, m-and p-hydroxybenzoic, vanillic, chlorogenic, caffeic, syringic, o- m-, and p-coumaric, ferulic, and syringic acids.
Bilberry juice