Mean rot severity (%) of JA tubers treated with caraway essential oil and infected with S. rolfsii using two storage methods.
Abstract
Essential oils, as natural sprout inhibitor and safe fungicides, are a promising tool and good alternative compounds otherwise synthetic due to their high efficacy, biodegradability, eco-safety and volatile nature. They are consisting of a number of various components, i.e., terpenes, phenols, alcohols, esters, aldehydes and ketones in different composition or combinations. These effective compounds supply excess to prevent sprouting in potatoes and Jerusalem artichoke (JA) and less chance to development of resistance in fungi in JA, strawberry and broccoli with low concentrations. On contrary, high concentration of these oils induce the germination of seeds like broccoli and carob. This chapter explains the practical application of using essential oils as natural antisprouting, inducing quality, preserving fungal diseases, eco-friendly compounds, alternating synthetic chemicals, giving high benefits and easy to apply. The foliar application with essential oils increases the productivity, quality and marketable yield and storability and reduces weight losses and decay. Moreover, the essential oils increase broccoli seed germination, antioxidant content and other phytochemical parameters. The chapter provides a novel anti-sprouting agent for inhibiting growth of processing potato tubers and identification of terpenoids that use to inhibit tuber sprouting as well as application of Chloropropham (CIPC) isopropyl-N-(3-chlorophenyl) carbamate as a conventional chemical inhibitor.
Keywords
- essential oils
- constituents
- anti-sprouting agent
- antifungal
- sprout growth
- postharvest
- vegetables
- structure
- extraction
- application
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 (
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 stored at 4°C and 90–95% relative humidity RH. In the second experiment, the tubers were stored in carton boxes (3 m3) 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
2.1.2 Important results
2.1.2.1 Antifungal activity of the essential oils
Assessment of antifungal activity in vitro of caraway and spearmint essential oils was evaluated against
2.1.2.2 Evaluation of the caraway essential oil and peat moss application under storage conditions
2.1.2.2.1 Severity of disease
Data presented in Table 1 show the rot fugal disease severity of JA tubers exposed to caraway oil and infected with fungal pathogen
Moreover, the activity of
2.1.2.2.2 Sprouting, weight loss and dry matter percentages of JA tubers
Table 2 show the mean data of weight loss and dry matter percentages of JA tubers exposed to emulsion of caraway essential oil and infected with fungal pathogenic
Criterion | Storage method* | Treatment** | Storage period (day) | |||
---|---|---|---|---|---|---|
30 | 60 | 90 | 120 | |||
Sprouting | 1 | C | 40.0 ± 10.0 | 70.0 ± 4.0 | 90.0 ± 4.0 | NA |
P | NA*** | NA | NA | NA | ||
O | 0.0 | 0.0 | 0.0 | 0.0 | ||
O + P | 3.8 ± 0.1 | 3.9 ± 0.1 | 4.0 ± 0.4 | 4.3 ± 0.2 | ||
2 | C | 50.0 ± 10.0 | 80.0 ± 14.0 | 95.0 ± 6.0 | 98.0 ± 2.0 | |
P | 3.6 ± 0.4 | 4.8 ± 0.4 | NA | NA | ||
O | 0.0 | 0.0 | 0.0 | 0.0 | ||
O + P | 0.0 | 0.0 | 0.0 | 0.0 | ||
Weight loss | 1 | C | 20.5 ± 2.9 | 35.7 ± 5.3 | 59.9 ± 8.0 | NA |
P | NA | NA | NA | NA | ||
O | 0.0 | 0.0 | 0.0 | 0.0 | ||
O + P | 2.9 ± 0.2 | 3.0 ± 0.2 | 3.8 ± 0.6 | 4.6 ± 0.5 | ||
2 | C | 7.1 ± 0.2 | 21.7 ± 3.3 | 50.9 ± 5.8 | 70.9 ± 8.2 | |
P | 30.7 ± 4.0 | 39.5 ± 9.9 | NA | NA | ||
O | 0.0 | 0.0 | 0.0 | 0.0 | ||
O + P | 0.0 | 1.0 ± 0.1 | 1.0 ± 0.2 | 1.7 ± 0.4 | ||
Dry matter weight | 1 | C | 17.2 ± 0.5 | 18.0 ± 0.7 | 19.2 ± 1.5 | NA |
P | NA | NA | NA | NA | ||
O | 22.5 ± 0.4 | 22.9 ± 0.6 | 23.6 ± 0.3 | 24.9 ± 0.6 | ||
O + P | 22.0 ± 0.2 | 22.3 ± 0.4 | 23.3 ± 0.9 | 23.5 ± 0.8 | ||
2 | C | 22.6 ± 0.4 | 23.0 ± 0.3 | 21.0 ± 0.5 | 21.5 ± 1.1 | |
P | 18.6 ± 0.6 | 17.0 ± 0.5 | NA | NA | ||
O | 23.6 ± 0.5 | 24.6 ± 0.8 | 24.9 ± 0.5 | 25.8 ± 0.5 | ||
O + P | 23.5 ± 0.4 | 23.7 ± 0.6 | 24.2 ± 0.4 | 25.5 ± 0.3 |
2.1.2.2.3 Biochemical constituents of JA tubers
Table 3 show the data of carbohydrates content, inulin and protein in JA tubers exposed to emulsion of caraway essential oil and then infected with fungal pathogenic
Criterion | Storage method* | Treatment** | Storage period (day) | |||
---|---|---|---|---|---|---|
30 | 60 | 90 | 120 | |||
Carbohydrates | 1 | C | 42.5 ± 1.4 | 41.7 ± 1.5 | 38.4 ± 4.3 | NA |
P | NA*** | NA | NA | NA | ||
O | 44.6 ± 1.3 | 44.2 ± 1.3 | 43.3 ± 1.3 | 43.0 ± 1.0 | ||
O + P | 42.7 ± 1.7 | 42.0 ± 0.7 | 41.6 ± 1.1 | 41.3 ± 0.3 | ||
2 | C | 42.0 ± 0.3 | 40.2 ± 1.4 | 37.7 ± 1.0 | 36.0 ± 0.5 | |
P | 36.7 ± 1.4 | 36.0 ± 0.3 | NA | NA | ||
O | 46.0 ± 0.3 | 46.9 ± 0.5 | 47.0 ± 0.8 | 47.7 ± 0.9 | ||
O + P | 42.0 ± 0.8 | 41.9 ± 0.7 | 41.5 ± 1.2 | 41.0 ± 1.4 | ||
Inulin | 1 | C | 14.2 ± 0.6 | 13.6 ± 0.7 | 12.8 ± 1.2 | NA |
P | NA | NA | NA | NA | ||
O | 15.6 ± 0.8 | 15.0 ± 0.3 | 16.7 ± 0.6 | 15.0 ± 0.2 | ||
O + P | 14.9 ± 0.6 | 14.0 ± 0.1 | 14.0 ± 0.0 | 13.9 ± 0.4 | ||
2 | C | 14.3 ± 0.5 | 14.0 ± 0.4 | 13.8 ± 0.6 | 13.0 ± 0.2 | |
P | 13.0 ± 0.4 | 12.0 ± 0.3 | NA | NA | ||
O | 18.9 ± 0.5 | 18.0 ± 0.4 | 17.9 ± 0.2 | 17.6 ± 0.6 | ||
O + P | 17.9 ± 0.5 | 17.6 ± 0.8 | 17.0 ± 0.2 | 17.0 ± 0.0 | ||
Protein | 1 | C | 12.2 ± 0.4 | 12.0 ± 0.2 | 11.9 ± 0.4 | NA |
P | NA | NA | NA | NA | ||
O | 12.8 ± 0.3 | 12.7 ± 0.3 | 12.7 ± 0.4 | 12.6 ± 0.4 | ||
O + P | 12.6 ± 0.5 | 12.6 ± 0.2 | 12.4 ± 0.1 | 12.0 ± 0.1 | ||
2 | C | 12.5 ± 0.3 | 12.3 ± 0.4 | 12.0 ± 0.4 | 11.9 ± 0.2 | |
P | 9.9 ± 0.2 | 9.0 ± 0.4 | NA | NA | ||
O | 13.0 ± 0.3 | 13.0 ± 0.6 | 12.7 ± 0.5 | 12.7 ± 0.2 | ||
O + P | 12.6 ± 0.5 | 12.4 ± 0.5 | 12.3 ± 0.4 | 12.0 ± 0.4 |
2.1.2.2.4 Peroxidase, polyphenoloxidase enzymes and phenol content in JA tubers
The mean activities data of peroxidase, polyphenoloxidase and phenol contents of JA fresh tubers treated with caraway essential oils and infected with pathogenic fungi over the use of two different two storage methods are presented on Table 4. Results revealed that infection with
Criterion | Storage method* | Treatment** | Storage period (day) | |||
---|---|---|---|---|---|---|
30 | 60 | 90 | 120 | |||
Peroxidase | 1 | C | 0.40 ± 0.02 | 0.30 ± 0.0 | 0.28 ± 0.05 | NA |
P | NA*** | NA | NA | NA | ||
O | 0.40 ± 0.03 | 0.38 ± 0.01 | 0.38 ± 0.01 | 0.37 ± 0.02 | ||
O + P | 2.67 ± 0.16 | 2.69 ± 0.26 | 2.73 ± 0.04 | 2.74 ± 0.03 | ||
2 | C | 0.23 ± 0.01 | 0.22 ± 0.02 | 0.21 ± 0.01 | 0.20 ± 0.06 | |
P | 1.90 ± 0.02 | 1.92 ± 0.03 | NA | NA | ||
O | 0.33 ± 0.02 | 0.34 ± 0.02 | 0.34 ± 0.02 | 0.34 ± 0.03 | ||
O + P | 1.77 ± 0.03 | 1.86 ± 0.04 | 1.87 ± 0.02 | 1.87 ± 0.26 | ||
Polyphenoloxidase | 1 | C | 0.39 ± 0.01 | 0.36 ± 0.01 | 0.35 ± 0.02 | NA |
P | NA | NA | NA | NA | ||
O | 0.47 ± 0.03 | 0.47 ± 0.02 | 0.45 ± 0.03 | 0.42 ± 0.06 | ||
O + P | 1.46 ± 0.02 | 1.57 ± 0.05 | 1.47 ± 0.02 | 1.57 ± 0.03 | ||
2 | C | 0.40 ± 0.04 | 0.40 ± 0.03 | 0.37 ± 0.03 | 0.35 ± 0.03 | |
P | 1.49 ± 0.03 | 1.50 ± 0.04 | NA | NA | ||
O | 0.46 ± 0.02 | 0.43 ± 0.01 | 0.41 ± 0.06 | 0.40 ± 0.01 | ||
O + P | 1.46 ± 0.02 | 1.57 ± 0.02 | 1.57 ± 0.03 | 1.67 ± 0.02 | ||
Total phenol | 1 | C | 0.29 ± 0.02 | 0.28 ± 0.01 | 0.27 ± 0.01 | NA |
P | NA | NA | NA | NA | ||
O | 0.32 ± 0.03 | 0.32 ± 0.03 | 0.32 ± 0.02 | 0.31 ± 0.02 | ||
O + P | 0.52 ± 0.02 | 0.52 ± 0.02 | 0.51 ± 0.02 | 0.52 ± 0.01 | ||
2 | C | 0.35 ± 0.02 | 0.35 ± 0.02 | 0.35 ± 0.02 | 0.34 ± 0.03 | |
P | 0.57 ± 0.04 | 0.57 ± 0.04 | NA | NA | ||
O | 0.26 ± 0.01 | 0.26 ± 0.01 | 0.26 ± 0.02 | 0.26 ± 0.02 | ||
O + P | 0.55 ± 0.02 | 0.55 ± 0.02 | 0.55 ± 0.01 | 0.56 ± 0.01 |
2.2 Inhibition of sprout growth and increase storability of processing potato by antisprouting agent
2.2.1 Methodology
2.2.1.1 Tuber material
Fresh local potato cv. Fridor and uniformly size of 60–80 mm in diameter (weighing 180–250 g) were selected without any sprouting in eyes and no anti-sprouting treatment was used. Each treatment was treated with natural and safe antisprouting agent and stored at ambient temperature (average: 35/15°C day/night and 70% RH) in Laboratory for 4 months.
2.2.1.2 Treatments
The experiment included seven treatments, which were as follows:
2.2.2 Results and discussion
2.2.2.1 Sprouting, weight loss and dry matter content
All control tubers had significant values of sprouting and weight loss percentages at the end of storage period (Table 5). Geraniol and citral completely inhibited sprouting by 100%, decreased weight loss and increase tuber dry matter content in both seasons. Application of geranyl acetate inhibited sprouting by 95%. On the other hand, linalool and l-carvone had no significant effect on tuber sprouting. It has been reported that l-carvone and d-carvone displayed little or no inhibition of sprouting in potatoes [17]. Geraniol and citral have a high content in monoterpenes such as benzaldehyde, eugenol and thymol [23]. CIPC inhibited sprouting over 98.5%.
Treatments | Sprouting (%) | Weight loss (%) | Dry matter (%) | |||
---|---|---|---|---|---|---|
2012 | 2013 | 2012 | 2013 | 2012 | 2013 | |
1. Control | 100.0a | 96.00a | 25.12a | 26.18a | 21.65f | 22.80e |
2. CIPC | 2.49e | 1.20c | 4.33e | 2.80ef | 23.60a–d | 23.66d |
3. Geranyl acetate | 4.68d | 4.33c | 3.41f | 4.65d | 22.50ef | 24.55ab |
4. Geraniol | 0.00f | 0.00c | 2.19h | 1.45g | 24.56a | 25.30a |
5. Camphor | 6.92c | 5.98c | 2.88g | 2.95ef | 23.33b–e | 24.38bc |
6. Citral | 0.00f | 0.00c | 1.51i | 1.26g | 24.00ab | 24.95ab |
7. Linalool | 100.00a | 72.00b | 9.50b | 8.00b | 22.66de | 23.60d |
8. l-Carvone | 70.58b | 62.00b | 9.50b | 6.25c | 22.80c–e | 23.70cd |
9. d-Carvone | 72.00b | 76.98b | 8.03c | 3.45e | 22.90c–e | 24.89 ab |
10. d-Citronellol | 2.89e | 2.00c | 6.75d | 5.73c | 23.60a−d | 24.68ab |
11. l-Citronellol | 0.00f | 0.00c | 2.25gh | 2.10fg | 23.80a–c | 24.55ab |
Under this study condition, the beneficial effect of the applied anti-sprouting agent (geraniol and citral) on controlling tubers sprouting and increasing dry matter content could be associated with their similar advantages effect in preservation of their tubers starch, carbohydrates, sugars and amino acid content (Table 6). Suppression of sprouting and weight loss logically associated with maintenance of dry matter. Furthermore, monoterpenes acts as antioxidant and had a protective role against oxidative stress under normal conditions of storage.
Treatments | Reducing sugars (%) | Total free amino acids (%) | Peroxidase activity POD (%) | |||
---|---|---|---|---|---|---|
2012 | 2013 | 2012 | 2013 | 2012 | 2013 | |
1. Control | 4.29a | 4.52a | 0.352a | 0.348a | 56.77g | 55.51g |
2. CIPC | 2.05c | 3.18d | 0.307ab | 0.301ab | 95.81b | 94.63b |
3. Geranyl acetate | 1.39cd | 3.93b | 0.084bc | 0.047c | 79.75e | 79.33e |
4. Geraniol | 1.24d | 1.51f | 0.030c | 0.028c | 97.33a | 96.29a |
5. Camphor | 3.41b | 3.48c | 0.152a–c | 0.153a–c | 80.68e | 80.26e |
6. Citral | 1.25d | 1.52f | 0.045c | 0.045c | 97.68a | 96.46a |
7. Linalool | 4.07ab | 4.13b | 0.106bc | 0.108bc | 80.67e | 79.06c |
8. l-Carvone | 3.81ab | 1.83e | 0.084bc | 0.151a–c | 81.67e | 80.50e |
9. d-Carvone | 1.45 cd | 1.68ef | 0.146a–c | 0.157a–c | 77.55f | 76.77f |
10. d-Citronellol | 1.76cd | 1.54f | 0.186a–c | 0.187a–c | 84.50d | 83.62d |
11. l-Citronellol | 1.29d | 1.58f | 0.147a–c | 0.059c | 87.67c | 86.65c |
2.2.2.2 Reducing sugars, amino acids and peroxidase POD activity
All storage treatments gave significant lower values on reducing sugars and amino acids content during two seasons of study as compared to the control (Table 6). In the ambient temperature, the lowest significant values of reducing sugars and amino acids content were found in tubers exposed to emulsion of geraniol and citral, without significant difference between the two treatments.
The monoterpenes rich in compounds had a potential role in preservation and maintenance of the stored tubers reserves, keeping the enzymatic activities in a minimal level and in more stable case thereby prolonged their dormancy period. Also, application of these treatments were highly effective in tuber protection against the degradable effects of oxidative stressful during high temperature storage conditions and accordance to the findings of [20] who indicated that monoterpenes and antioxidants tended to slow down the activity of carbohydrates, breakdown of protein and enzymatic activity as well as reduce respiration rate and metabolism enzyme. The role of POD in sprouting of potatoes was widely reported, particularly its degrading activity of IAA, and cytokinin which is considered an effective promote oxidative stress is of great importance and depending on the activation degree of peroxidase as affected by storage treatments.
2.2.2.3 Processing quality of potato fries and chips
All storage treatments and CIPC treatment at ambient temperature had significant differences on quality characters of potato chips and French fries, i.e., color, crispiness and taste in comparison with the control treatment (Table 7).
Treatments | Chips | French fries | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Color | Taste | Crispness | Color | Taste | Crispness | |||||||
2012 | 2013 | 2012 | 2013 | 2012 | 2013 | 2012 | 2013 | 2012 | 2013 | 2012 | 2013 | |
1. Control | 3.00e | 3.33c | 3.00d | 3.33bc | 4.33a–c | 4.33a–c | 3.33 de | 3.00 d | 3.33cd | 4.00b–d | 4.67ab | 4.67 ab |
2. CIPC | 3.33de | 3.33c | 4.33a–c | 4.33ab | 4.33a–c | 4.67ab | 3.67 cde | 3.33 cd | 4.00a–c | 4.33a–c | 4.67ab | 4.67 ab |
3. Geranyl acetate | 4.67ab | 4.67ab | 5.00a | 4.67a | 5.00a | 5.00a | 4.67ab | 4.67ab | 5.00a | 4.67ab | 5.00a | 4.33 abc |
4. Geraniol | 5.00a | 5.00a | 5.00a | 4.67a | 5.00a | 5.00a | 4.67ab | 4.67ab | 5.00a | 4.67ab | 5.00a | 4.33 a–c |
5. Camphor | 4.67ab | 4.67ab | 5.00a | 4.67a | 5.00a | 5.00a | 4.67ab | 4.67ab | 4.67 ab | 4.67ab | 5.00a | 5.00a |
6. Citral | 5.00a | 5.00a | 5.00a | 4.67a | 5.00a | 5.00a | 5.00a | 5.00a | 4.67ab | 5.00a | 5.00a | 5.00a |
7. Linalool | 4.67ab | 4.67 ab | 4.64ab | 4.67a | 5.00a | 5.00a | 4.67ab | 4.67ab | 4.67ab | 4.67ab | 5.00a | 5.00a |
8. l-Carvone | 4.67ab | 4.67ab | 4.67ab | 4.67a | 5.00a | 5.00a | 4.67ab | 4.67ab | 5.00a | 5.00a | 5.00a | 5.00a |
9. d-Carvone | 5.00a | 5.00a | 5.00a | 4.67a | 5.00a | 5.00a | 5.00a | 5.00a | 4.67ab | 5.00a | 5.00a | 5.00a |
10. d-Citronellol | 4.00b–d | 4.67ab | 4.67ab | 4.67a | 4.67ab | 4.67a | 4.00b–d | 4.00a–c | 4.33a–c | 4.33a–c | 4.67ab | 5.00a |
11. l-Citronellol | 4.33a–c | 4.67ab | 4.67ab | 4.67a | 4.67ab | 4.67a | 4.00b–d | 4.33a–c | 3.67b–d | 4.33a–c | 4.67ab | 4.67ab |
The same treatments prevented and blocked the accumulation of total sugars, and kept the reducing sugars and amino acids in optimize levels in the stored tubers at ambient temperature. This is true in the end of storage (4 months). Thus, we noticed the worst processing quality (dark potato chips and crispness with bad taste) of storage treatments due to the appearance of Millard reaction during frying process and the accumulation of reducing sugars and amino acids [23]. The same processing quality parameters were correlated with dry matter content (Table 8) and with amino acids content (Table 9) in both seasons. These results are in harmony with those previously obtained by [24]. Meanwhile, we also noticed that the best processing quality of basic constituents of essential oils produced chips, the optimization of reducing sugars and amino acids of their tubers thereby, the prevention of Millard reaction occurrence during frying processes and thus it turn reflects on best color, crispiness and taste.
Treatment | Seed germination index [%] | Seed germination [%] | Seedling length [cm] | Seedling vigor index [cm] | Yield [g]container/242 cm2 | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|
2012 | 2013 | 2012 | 2013 | 2012 | 2013 | 2012 | 2013 | 2012 | 2013 | ||
1 | Water (control) | 13.36e | 12.96d | 86.67c | 86.0a | 4.67c | 4.00b | 4.03c | 3.44c | 36.40e | 34.20d |
2 | Hot water | 14.61de | 13.02d | 93.78b | 90.44bc | 5.00c | 4.80b | 4.71c | 4.33c | 40.88de | 37.21d |
3 | Fennel oil | 22.01a | 23.01a | 97.33ab | 97.33a | 7.33ab | 7.67a | 7.13ab | 7.47ab | 56.90b | 49.17c |
4 | Caraway oil | 21.94a | 22.88a | 97.33ab | 99.00a | 8.00ab | 8.33a | 7.79a | 8.25a | 54.97bc | 67.75a |
5 | Basil oil | 20.22ab | 21.82ab | 94.67b | 92.33b | 7.00b | 7.67a | 6.63b | 7.07b | 64.87a | 68.17a |
6 | Thyme oil | 18.81bc | 20.14b | 100.00a | 100.0a | 8.20a | 8.30a | 8.20a | 8.30a | 66.54a | 67.75a |
7 | Sage oil | 16.91cd | 17.76c | 100.00a | 100.0a | 7.83ab | 7.83a | 7.83a | 7.83ab | 47.83cd | 49.17c |
Treatment | Total phenolic acid (mg/100 g F.W.) | Total flavonoids (mg/100 g F.W.) | Anthocyanin (mg/100 g F.W.) | Ascorbic acid (mg/100 g F.W.) | DPPH (Mmol TE/g F.W.) | ||||||
---|---|---|---|---|---|---|---|---|---|---|---|
2012 | 2013 | 2012 | 2013 | 2012 | 2013 | 2012 | 2013 | 2012 | 2013 | ||
1 | Water (control) | 83.33d | 84.11e | 91.99d | 95.18e | 7.13d | 7.70d | 70.58e | 81.23d | 23.66a | 24.66a |
2 | Hot water | 88.71c | 88.56c | 100.95c | 101.03d | 8.62c | 8.77c | 86.81c | 86.81c | 23.54b | 23.66a |
3 | Fennel oil | 88.46c | 88.90c | 107.66b | 107.72c | 8.86c | 8.87bc | 87.66c | 88.00c | 21.98d | 21.98c |
4 | Caraway oil | 87.90c | 88.13cd | 104.66b | 104.73c | 9.84bc | 9.84bc | 77.33d | 85.80c | 21.96de | 21.96c |
5 | Basil oil | 122.06b | 122.29b | 113.00a | 113.00b | 11.71a | 12.05a | 94.67b | 94.67b | 21.94de | 21.94c |
6 | Thyme oil | 131.66a | 131.60a | 115.66a | 116.24a | 12.09a | 12.14a | 102.33a | 103.33a | 21.86e | 20.03d |
7 | Sage oil | 87.9c | 84.74de | 104.33bc | 104.59c | 10.38b | 10.38b | 82.33cd | 86.69c | 22.79c | 22.79bc |
2.3 Increasing antioxidant content of broccoli sprouts using essential oils during cold storage
2.3.1 Methodology
2.3.1.1 Plant material and germination condition
(
2.3.1.2 Application and extraction of essential oils
The essential oils of fennel seeds (
2.3.2 Results and discussion
2.3.2.1 Vegetative characters of broccoli sprout
All essential oil treatments rich in antioxidant stimulate the germination of broccoli seeds. All essential oils treatments significantly increased germination, germination index, seedling length, seedling vigor index and container yield compared with the control (tap water) during the two seasons (Table 8). The essential oils of fennel, caraway and thyme increased the seed germination index by 171.43, 170.29 and 148.02%, respectively, compared to the control 100%. The increases of seed germination % over the control reached to 12.73, 13.74 and 15.82% for the effective treatments, respectively. The essential oils of thyme, caraway and fennel had significant increases in seedling vigor and yield container over the control to 50.25, 73.82 and 90.22%, respectively.
The allelochemical effects of essential oils for induce stimulatory or inhibitory of seed germination and other physiological process varied depending on the dose, tested species, concentration and basic components. Under our study, the lower doses of essential oils had a stimulatory effect [25]. The obtained results reveal that the applications of essential oils at a low level improve seed germination of broccoli. However, application of thyme oil reaches 100% of sprouts after seed germination (Table 8). Impact of essential oils on seed germination of other plant species was reported as 24 out of 47 tested terpenoids enhanced the seed germination of
2.3.2.2 Phytochemical characters
All treatments significantly surpassed over the control in Broccoli sprout bio-constituents, i.e., total phenolic acid, total flavonoids, anthocyanin and ascorbic acid, while the control treatment gave the highest DPPH radical scavenging capacity (Table 9). Application of thyme oil treatment produced significant increases of total phenol, total flavonoids, anthocyanin and ascorbic acid content. Moreover, thyme and basil essential oils decreased significantly the DPPH free radical scavenging capacity. Accordingly, it has been chosen to study the storage behavior characters, in addition to control treatment. The majority of the antioxidant activity attributes to phenolic compounds, flavonoids and ascorbic acidin essential oils [27]. Moreover, the effect of antioxidant on DPPH free radicle was due to the presence of hydroxyl groups in their chemical structure. In this respect, [28] found that the oregano essential oil inhibited hydro-peroxide formation and that the CHO fraction showed the highest antioxidants activity.
The thyme oil showed significant lowest radical scavenging capacity compared to the control and other treatments (Table 9). All other antioxidants/essential oils showed high and almost the same antioxidant capacity effect. It was known that the free radical scavenging DPPH intensity of some compounds can be influenced by their different kinetic behavior [29]. For slow reacting compounds the influence was attributed to the complex reacting mechanism. In our study, probably, the constituents from thyme essential oil involved one or more secondary reactions, which result the slower reduction of DPPH solutions [29].
2.3.2.3 Antioxidant activity during cold storage
2.3.2.3.1 Total phenolic compounds and DPPH radical scavenging capacity
Figure 2 illustrate that there was a gradual increase in the total phenolic acid content, and reaching a maximum value at day 5 and 10 (132.67 and 135.04 mg GAE/100 g F.W.) compared to the initial time. This concentration decreased in to 129.03 mg at day 15 due to thyme oil application (Figure 2). Keeping in view that the control treatment decreased to 73.84 GAE/100 g FW at day 5. On the 15th day, the old-sprout from storage, the control was reduced by 28.57% compared to thyme oil (1.98%). The control treatment of antioxidant capacity increased significantly until day 10 (29.43 mg/100 g F.W.), and finally decrease (28.46% mg 100/g F.W.) at day 15 increased from initial period (20.28%). While, application of thyme oil the change was not clear at the end of storage (1.98%) (Figure 3). During cold storage (Figure 3), the control was reduced DPPH by 28.57% compared to thyme oil at 15 day old-sprout (1.98%). Nath et al. [30] observed a constant decrease in the antioxidant capacity for 144 h of storage of broccoli inflorescences. This behavior in DPPH may be due to the steady changes in plant metabolism during storage period as a result of oxidative stress, which may include structural and chemical changes in synthesis or antioxidant content [31].
2.3.2.3.2 Total flavonoids
Total flavonoids (Figure 4) were found in a higher concentration in 3-day-old sprouts of thyme treatment, with values of 115.95 mg/100 g F.W., after 5 and 10 days of storage slight decrease to 0.021 and 0.086%, respectively, when compared with the initial value, and finally reduced by 1.39%. The high loss of flavonoids reached to 10.59 and 47.89%, after 5 and 10 days, respectively, and at 15 days the loss increased to 58.33% for control treatment (average two seasons).
2.3.2.3.3 Glucosinolates content
Storage time had significant differences in glucosinolates content of the samples analyzed. Figure 5 illustrate that the thyme oil increased significantly glucosinolates content in 3-day-old sprouts, compared to control treatments. Moreover, thyme oil had a high value of total glucosinolates (27.02 μg/g F.W.) and slightly decreased up to 26.43 μg/g F.W. on day 15. At the end of storage, the decreasing changes percent was about 2.18%. In the control treatment, the highest decrease in total glucosinolates content was observed, where reached about 49.12% at the end of storage.
2.3.2.3.4 Glucosinolates content of mature head versus sprout broccoli
In sprout, the total glucosinolates level (27.02 μg/g F.W.) is higher than in florets or heads (7.37) (Figure 6). Glucoraphanin is the powerful of antioxidant and the most abundant aliphatic glucosinolates present in sprout. The glucoraphanin reached the highest 16.24 followed by glucoerucin 5.9 and glucoiberm 1.2 μg/g F.W. On the other hand, the florets/heads contain the highest level of aromatic/indolylglucosinolates, neoglucobrassicin (2.11) followed by glucobrassicin (1.67). Our results are in agreement with those obtained by [32].
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