**Assessment of the Potential Use of Young Barley Shoots and Leaves for the Production of Green Juices**

**Agata Blicharz-Kania 1, Dariusz Andrejko 1, Franciszek Kluza 1, Leszek Rydzak 1,\* and Zbigniew Kobus <sup>2</sup>**


Received: 9 June 2019; Accepted: 19 July 2019; Published: 21 July 2019

**Abstract:** It is possible to use the aboveground parts of barley, which are cultivated as a forecrop. They are often simply composted or dried for bedding. It is worth trying other more effective methods of processing aboveground biomass. The aim of this study was to preliminary investigate the possibility of using young barley leaves and shoots for the production of green juice with potential health properties. The material was collected at days 7, 14, 21, and 28 after plant emergence. The length and strength of the shoots were measured and the pressing yield was calculated. The pH value and the content of protein, chlorides, and reducing sugars were also determined. The juice was additionally subjected to pasteurisation and freezing, and changes in pH and chlorophyll content occurring during storage were determined. The pressing yield of young barley leaves and shoots was estimated to be between 69% and 73%. The product was characterised by a high content of total protein (34.45%–51.81%d.w.) and chlorophylls (6.62 mg·g<sup>−</sup>1). The chlorophyll content declined during barley juice storage. Pasteurisation of the juice from young barley leaves does not induce statistically significant changes in the pH of the juice, but reduces the chlorophyll content. Our results revealed that the most effective way to preserve the green juice is by freezing. This process does not induce changes in juice acidity and only slightly reduces the chlorophyll content during storage of the product.

**Keywords:** juice; barley; pressing; protein; chlorophylls; green food

### **1. Introduction**

In order to improve the soil quality and protect it from weeds and, consequently, obtain a better crop of the cultivated plant, producers often use forecrop cultivation. Depending on what kind of plant will be grown, an appropriate forecrop will be selected. For cereals, the best options are root crops (mainly potatoes), legumes, or rapeseed. However, when growing vegetables, such as tomatoes, carrots, or white cabbage, it is better to use a cereal forecrop, and rye, wheat, or barley can be used [1]. These cereals can be used via two techniques. The first method involves ploughing whole plants and using them as a fertilizer. Plants that are a forecrop can also be cut. Then, only roots and postharvest residues are ploughed. In the case of the latter method, it is possible to continue using the green parts of the plants, which are often simply composted or dried for bedding.

Recently, products from young barley leaves and shoots have gained popularity. They are available in a variety of forms, i.e., juice, tablets, or powder. Young parts of plants are a source of phenolic acids and many vitamins, e.g., C, E, and B group vitamins. Additionally, barley grass contains substantial amounts of carotenoids, folic acid, calcium, iron, magnesium, potassium, zinc, and copper. Importantly, products obtained from cereal leaves and shoots can be used as supplements in a high-protein diet. Barley grass contains approximately 30% of protein in dry matter [2–4]. The

chemical index of nutritional value (Chemical Score, CS) is 41.44% (Methionine) [5]. Barley shoots and leaves are also a source of chlorides. Naturally occurring chlorides exert a beneficial effect on organism function. Chloride ions participate in the regulation of water, as well as electrolyte metabolism and maintaining acid–base balance [6].

One of the most important active compounds in "green food" is chlorophyll. Seed plants contain type A and B chlorophylls, which differ according to the type of substituent on the second pyrrole ring. However, these pigments are unstable. Many factors, e.g., UV radiation or pH and temperature changes, cause chlorophyll degradation in food products. Chlorophylls are a valuable source of magnesium; they can also improve metabolism and eliminate unpleasant mouth odours. Additionally, they have antibacterial and anti-inflammatory properties, remove toxins from the liver and blood [7–11], and even act as a haemoglobin substitute [12].

The consumption of green juices has therapeutic properties: it exerts an antidiabetic effect, regulates blood pressure, strengthens immunity, protects the liver, and has anti-acne and antidepressant activities. It also improves the function of the digestive tract and prevents hypoxia, cardiovascular diseases, fatigue, and constipation. Additionally, it alleviates atopic dermatitis and has anti-inflammatory, antioxidant, and anticancer effects [4]. Kubatka et al. [13] have demonstrated positive changes in tumour cells in rats treated with juice from young barley leaves. A significantly more pronounced effect of the therapeutic treatment was observed in a study group receiving a diet supplemented with the juice. It has also been confirmed that supplementation of the diet with barley leaf powder can relieve the clinical symptoms of diabetes [14]. Additionally, barley grass contains substantial amounts of dietary fibre (mainly an insoluble fraction), which has a positive effect on metabolism through regulating the appetite and, thus preventing the development of overweight. Son et al. [3] recommend enrichment of the diets of young children using valuable nutrients from young barley leaves.

Products from young barley leaves have been used in East Asia for a long time. Currently, they are available in supermarkets, as well as online, in the United States and many European countries. The increase in consumer awareness has contributed to an appreciation of the health benefits of "green food" [8]. A number of products based on young cereal leaves are recommended as dietary supplements and, hence, are currently being manufactured to be purchased in pharmacies.

There is a paucity of scientific publications confirming the health-promoting properties of the juice from young barley leaves. There are also no preliminary investigations describing the impact of production and processing on the quality of green juices. Furthermore, the relationship between the date of raw material harvesting and the pressing process, as well as the content of nutrients—including proteins—in the juice, has not yet been analysed. Another unexplored area is the changes occurring in the chlorophyll content of barley juice, depending on the thermal treatment. Knowledge of these relationships has great practical significance as it provides information on methods for the acquisition of a product with a high nutritional value and, at the same time, ensures the longest possible growth period for the plant (and, thus, the greatest mass of roots to be used as forecrop).

The aim of this work was to preliminary examine the efficiency of the process of pressing green juice from young barley leaves and shoots and to determine the chemical composition of the product obtained. An additional goal of the research was to compare the effect of preservation methods like pasteurization and freezing on the chlorophyll content and pH of barley juice.

#### **2. Materials and Methods**

#### *2.1. Research Material*

Barley grain cv. Kangoo was used for the investigations. The seeds, weighing 5 kg, were sown under laboratory conditions (Figure 1). No fertilisation was applied during the cultivation. The material was collected at days 7, 14, 21, and 28 after plant emergence. The crop area was divided into four parts, and these four parts were then divided again into 12 smaller ones. Three parts from the whole field were chosen at random for each series of investigation (different harvest time: 7, 14, 21, and 28 days). Each sample of shoots and leaves of young barley for juice production weighed 200 g.

**Figure 1.** Cultivation of barley.

#### *2.2. Measurement of Physical Properties*

Samples without mechanical damage were selected for determination of the length and strength of the barley. The length of five barley shoots was measured with the use of a calliper to the nearest 0.01 mm. The shoot strength was determined by applying a uniaxial tensile test to the leaves. The test was carried out using a Zwick/Roell Z0.5 materials testing machine (Zwick.Roell AG, BT1-FR0.5TN.D14, Ulm, Germany) equipped with a measuring head at a maximum force of 50 N (travel speed <sup>=</sup> 50 mm·min<sup>−</sup>1). Tensile strength was applied to the material until rupture. TestXpert II software (Zwick/Roell AG, Ulm, Germany) was used to assess the force required for destruction of the barley grass.

#### *2.3. Pressing*

The juice was squeezed from barley grass (with a weight of 200 g for each repetition) using a press designed for pressing green plant leaves, i.e., Manual Juicer BL-30 (BioChef, Byron Bay, NS, Australia).

The pressing efficiency was calculated using the following equation:

$$\mathcal{W}\_{\dot{j}}(\%) = \frac{\mathcal{M}\_{\dot{j}}}{\mathcal{M}\_{\dot{i}}} \cdot 100 \tag{1}$$

where:

*Wj*—pressing yield, %; *Mj*—mass of juice after pressing, kg; *Mi*—mass of input material, kg.
