1. Introduction

Recently, the natural alternatives such as plant essential oils provide a promising control of plant diseases and anti-sprout agent because they virtually constitute a rich source of bioactive chemicals such as phenols, flavonoids, quinones, tannins, alkaloids, saponins, sterols terpenes, aromatic and aldehydes [1]. Moreover, these natural alternatives can also maintain the biochemical constituents of tubers during storage, they are biodegradable to nontoxic products, and are potentially suitable for use in integrated pest management programs.

Jerusalem artichoke JA or sun choke (Helianthus tuberosus L.) is a perennial plant which has a high economic value. JA used traditionally for human food and livestock feed due to its high nutritive value. JA tubers used for production of biofuels

(ethanol) and some functional food like inulin, fructooligosaccharides and fructose. Moreover, some bioactive metabolites from its leaves and stems have been used in some pharmaceutical industries [1]. Storage JA tuber, controlled rots can be done by various techniques including; cold temperature, removal of diseases in tubers and minimizing mechanical injuries or application of synthetic fungicides. Another simple applied method in developing countries is keeping the tubers in the soil. Unfortunately, many fungi diseases can grow at cold storage temperatures and lead to damage, especially in extending long storage [2], However, storage of the harvested tubers usually results in high losses in quality, caused mainly by desiccation, rotting, sprouting, freezing and inulin degradation. A common solution is the use of synthetic chemical fungicides, however, their use is accompanied by threatening human health and the environment by supporting the emergence of resistant pathogens and by contamination of food with the pesticide deposits [3]. Essential oils, as green fungicides, are emerging as a better alternative of synthetic fungicides due to their high efficacy, biodegradability, eco-safety and volatile nature.

stored at 4°C and 90–95% relative humidity RH. In the second experiment, the

Effect of Essential Oils on Storability and Preservation of Some Vegetable Crops

layers at the rate of peat moss: JA tubers (1.5: 1, kg/kg). The treatments applied for each experiment can be summarized as follows: Control (C), infected with fungal pathogen S. rolfsii (P), treated with caraway essential oil (O) and treated with caraway oil and infected with pathogen S. rolfsii (O + P). About 30 kg of tubers was

Assessment of antifungal activity in vitro of caraway and spearmint essential oils

inhibited the growth of the fungal pathogen even at the lowest concentration (2%). On the other hand, spearmint essential oil showed slight reduction in the fungal pathogen growth. The antifungal activity of caraway essential oil may be attributed to some antifungal phytochemicals that constitute a large fraction of the oil like

2.1.2.2 Evaluation of the caraway essential oil and peat moss application under storage

Data presented in Table 1 show the rot fugal disease severity of JA tubers exposed to caraway oil and infected with fungal pathogen S. rolfsii under the two storage methods. The disease severity increased with the increasing the storage period over to the storage methods. JA tubers infected with S. rolfsii and exposed to emulsion of caraway essential oil (O + P) in peat moss layer at 25°C significantly reduced the disease severity compared to the cold storage method after 4 months storage. Infected-control JA tubers (P) and storage in peat moss layer at 25°C significantly reduced the disease severity for 2 months of storage compared with cold storage method, after which, the tubers were fully decadent. On the other hand, control-uninfected JA tubers (C) and storage in peat moss layer at 25°C significantly reduced the disease severity (caused by reasons other than S. rolfsii) compared with the storage under cold storage method. Caraway essential oil had the antimicrobial effects due to its content of basic constituents of monoterpenes, carvone and limonene. The basic constituents had a permeability effect on fungal

Inhibition in mycelial dry weight of S. rolfsii as a function of the tested oils. Columns superscripted with the

same letter are not significantly different at P ≤ 0.05 (Duncan test).

was evaluated against S. rolfsii (Figure 1). Caraway essential oil completely

) at 25 2°C with moistened peat moss

tubers were stored in carton boxes (3 m<sup>3</sup>

DOI: http://dx.doi.org/10.5772/intechopen.87213

2.1.2.1 Antifungal activity of the essential oils

carvone, limonene, carveol, pinene and thujone [12].

used for each treatment.

2.1.2 Important results

conditions

2.1.2.2.1 Severity of disease

Figure 1.

101

Respiration of potato tubers during storage and breakdown of dormancy during storage result in sprouting and loss of nutritive value of tubers [4]. Sprouting reduces the weight, the nutritional and processing quality of tubers and the number of marketable potatoes, being responsible for important economic losses during potatoes storage [5]. These physiological changes affect the internal composition of the tuber and destruction of edible material and changes in nutritional quality [6]. Various methods are available to control sprouting during storage. The primary method to control sprouting in storage is with postharvest application of isopropyl N-(3-chlorophenyl) carbamate (chlorpropham; CIPC). CIPC inhibits sprout development by interfering with cell division [7]. Therefore, a pressing need exists to find other, more environmentally acceptable sprout inhibitors for tubers. Nowadays it's very important to use natural products compounds such as essential oils.

Broccoli sprouts are considered as a functional food. Essential nutrient content provides diverse secondary metabolites and phytochemicals [8]. The phenolic compounds, especially flavonoids and anthocyanin, show a great ability capture free radical that leading to oxidative stress, to these compounds are attributed a beneficial effect in the prevention of cardiovascular diseases, circulatory problems, neurological disorders and cancer [9]. Broccoli has been identified as a vegetable with potential anti-cancer activity due to high levels of glucosinolates. The use of essential oil treatments rich in antioxidant to stimulate broccoli seed germination should be considered. Application of thyme and basil oil at 4% reduced the pathogenic fungi from seed to seedling and had a positive effect on the seed germination of infected seeds [10]. Aromatic plants especially essential oils are well known for their antioxidant and antimicrobial properties that prevent food degradation and alteration [11], as they are rich in phenolic substances, usually referred to as polyphenols, which are ubiquitous components of plants and herbs.

## 2. Application of essential oils

#### 2.1 Alternative preservation method against sclerotium tuber rot of Jerusalem artichoke using natural essential oils

#### 2.1.1 Methodology

Two experiments were conducted in Mansoura laboratory for vegetable crop handling and postharvest according to the storage method. In the first experiment, the tubers were kept in perforated polyethylene bags (0.075 mm thickness), and

### Effect of Essential Oils on Storability and Preservation of Some Vegetable Crops DOI: http://dx.doi.org/10.5772/intechopen.87213

stored at 4°C and 90–95% relative humidity RH. In the second experiment, the tubers were stored in carton boxes (3 m<sup>3</sup> ) at 25 2°C with moistened peat moss layers at the rate of peat moss: JA tubers (1.5: 1, kg/kg). The treatments applied for each experiment can be summarized as follows: Control (C), infected with fungal pathogen S. rolfsii (P), treated with caraway essential oil (O) and treated with caraway oil and infected with pathogen S. rolfsii (O + P). About 30 kg of tubers was used for each treatment.
