The Effect Of Modified Atmospheric Biology Essay

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This project focuses on the effect of modified atmospheric conditions on the shelf life of the banana. Ethylene which is a hormone that is release by fruits is initially responsible for ripening. This hormone is very important in order to allow the progression of various cascade of reaction that is responsible for the changes in the fruits that we normally experience from time to time. These changes that often results as a consequence of the hormone ethylene include the following, change in colour, change in texture, taste and smell.

Ethylene has been used in practice since the ancient Egyptians, who would gas figs in order to stimulate ripening. The ancient Chinese would burn incense in closed rooms to enhance the ripening of pears. It was in 1864, that leaks of gas from street lights showed stunting of growth, twisting of plants, and abnormal thickening of stems (the triple response)(Arteca, 1996; Salisbury and Ross, 1992). In 1901, a russian scientist named Dimitry Neljubow showed that the active component was ethylene (Neljubow, 1901). Doubt discovered that ethylene stimulated abscission in 1917 (Doubt, 1917). It wasn't until 1934 that Gane reported that plants synthesize ethylene (Gane, 1934). In 1935, Crocker proposed that ethylene was the plant hormone responsible for fruit ripening as well as inhibition of vegetative tissues (Crocker, 1935). Ethylene is now known to have many other functions as well. 

Plants often release this hormone (ethylene) when they are damaged mechanically or by disease condition, the release of the hormone can induce a variety of changes in plants which is dependent on the age of the plant such as abscission of plant parts, shortening and bending of plant stems.

The property of this compound is very diverse and an increase concentrate level contributes to no toxicity to humans. Even though, ethylene is produced by certain fruits and also serves as the primary requirement for those fruit ripening it can be very detrimental to other fruits and vegetables. This is the reason why fruits such as banana, tomato, etc that is involves in the emission of highly concentrate ethylene are required to be stored separately from these substances since the influence of ethylene on these fruits and vegetable such as broccoli and cabbage may contributes to intense colour change.

One of the amazing thing is that all fruits are affected by ethylene differently for example cherries and blueberries produces little ethylene and thus are not influence by ethylene. Bananas, which is tropical fruit is very susceptible to low levels ethylene concentration. Many commercial companies produce and use ethylene invasively as a means of ripening certain postharvest fruits e.g. banana. In such conditions ethylene can become concentrated to levels that will hasten the ripening process.

Ethylene is responsible for the decrease in chlorophyll levels in plants as well as in the leaf of plants and vegetables, which is the reason why green leafy vegetables are not supposed to be stored with ethylene producing fruits.

Ethylene has most gases can penetrate most substances in fact it can permeate substances such as cardboard, wood and even concrete. Therefore ethylene's property being a gas and free moving make it very hard to control and thus the ability to diminish its influence on fruit has posed a major a problem.

The effect of ethylene even can be slower at lower temperatures. This effect has shown to decrease the synthesis of the hormone by fruits and thus slower the rate of ripening. There are also some chemically ways to control the effect of ethylene on fruits, these chemicals often binds to the ethylene receptors inhibiting this first messenger hormone from initialising a cascade of reaction that will result in the ripening of the fruit. Some of these chemicals which posses this property include the following other chemicals such as potassium permanganate (KMnO4) binds directly to ethylene decreasing its concentration in the atmosphere, thus lowering its effect on fruits.

Ethylene is produced in all higher plants and is produced from methionine in essentially all tissues. Production of ethylene varies with the type of tissue, the plant species, and also the stage of development. The mechanism by which ethylene is produced from methionine is a 3 step process (McKeon et al., 1995; Salisbury and Ross, 1992). 

ATP is an essential component in the synthesis of ethylene from methionine. ATP and water are added to methionine resulting in loss of the three phosphates and S-adenosyl methionine (SAM).

SAM can actually be recycled back to methionine through various reactions involving transamination reactions, which actually transfer to an amino group to give the final product methionine.

A 1-amino-cyclopropane-1-carboxylic acid synthase (ACC-synthase) facilitates the production of ACC from SAM. 

Oxygen is then needed in order to oxidize ACC and produce ethylene. This reaction is catalyzed by an oxidative enzyme called ethylene forming enzyme.

ACC synthase is the rate limiting step for ethylene production and it is this enzyme that is manipulated in biotechnology to delay fruit ripening in the "flavor saver" tomatoes (Klee and Lanahan, 1995). 

Oxygen is very essential molecule in the biosynthesis of (1-amino-cyclopropane-1-carboxylic acid) ACC, which in turn is responsible for the production of ethylene.

Therefore limiting the amount of oxygen exposure to fruits we should be able to inhibit the rate limiting step, which normally proceeds to the production of ethylene. This particular project was established using this concept, because it was unique and simple to postulate inexpensive ways and ideas of lowering the oxygen concentration. The most principle and inexpensive ways of lowering the oxygen concentration was by creating a partial vacuum that supposedly was efficient in lowering the number of gas molecules.

The idea of creating a partial vacuum serves as an inhibition to the ethylene biosynthesis reactions since we are limiting an essential molecule needed for the synthesis of ethylene as observe in the outline of the chemical reactions below.

As mentioned earlier the fruit that will be involve in this experiment is banana, banana is a tropical fruit that is predominantly grown in the tropics. It is one of the most natural and valuable source of some of the essential minerals such as calcium and potassium. It is vastly cultivated here in the tropics and subtropical areas.

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Background to the study

Banana is a tropical fruit that is grown in most tropical countries; it has a commercial value when exported. This particular fruit comprises of calcium and potassium, which are considered as some of the essential minerals for growth and development and such it is consume by many Guyanese. The uses of banana is so much diverse with some of these uses ranging from desert, milkshake and some can even serve as fries.

The storage of banana for shipment has posed a major issue due to its short shelf life and its high starch content. According to the International Conference on Nutrition (ICN) about 50% perishable fruits, vegetable and roots are lost due to lack of post harvest techniques, which translate into billions of dollars (IAEA report 1982). From the prevailing condition it seems that the lack of suitable preservation methods is a major factor contributing to the primary limitation to production and consumption of increased amount of the fruit (Forsyth 1980). Initial market assessments in current export markets and visits with producers and exporters in Guyana have shown the quality of fresh produce currently exported is uneven and in some instances very poor. Stages all along the export chain from harvest and pre-harvest to transportation and final export are all in need of improvement. Pre-harvest practices, sanitation at the packinghouse, packaging, bacterial and fungal problems, and transportation were all identified as areas where improvement could benefit the quality and increase the shelf life of Guyana's fresh produce (banana) exports. (Ministry of Fisheries, Crops and Livestock New Guyana Marketing Corporation National Agricultural Research Institute, 2003).

Export Quantity of Bananas in Guyana - 1961-2008

The graph above highlights the export quantity of bananas for the period of 1961 -2008; for 2002 the highest proportion of banana export was observed and for the succeeding years there was a decline from this quantity of export. Between 2002 and 2008, 2005 had the lowest quantity of banana export which might have subsequently occur as result of the 2005 flood. The fact that the number of banana being exported is decreasing emphasise the need for serious pre-harvest and post-harvest strategies. There are several successful initiatives that have been implemented in Guyana prior to the harvest of the banana. The bunch covers a method of treatment very common in Guyana for commercial pre-harvest bananas as been regarded to improve quality and yield of the fruit. Although the positive benefits of bunch cover application typically far outweigh the undesirable effects, it is important to point out several possible negative consequences. The use of non-perforated bunch covers in hot, humid climates such as Guyana may damage the bunch physiologically due to overheating, rotting, and premature ripening. In addition, insect pests may proliferate inside non-insecticide treated bunch covers. Another negative consequence of ineffective bunch covers is the economic loss due to the extra cost of the material and the labor needed for application. Perforated polyethylenes are often substituted in Guyana because Guyana is located within the tropical region. In spite of all this, Postharvest shelf life and market quality of plantains and bananas are significantly influenced by pre-harvest production practices.

Many people consume and utilise the fruit in Guyana and some are even exported to foreign countries thus quality and appearance of the fruit becomes a major significance. Market returns for bananas in

International markets are generally greatest for large fruit that are blemish-free (Johns, 1996). Consumers use visual quality to purchase fresh produce (Shewfelt, 1999;Shewfelt, 2009). External appearance and market quality of plantains and bananas are significantly influenced by pre-harvest production practices. The internal attributes such as taste, texture, sweetness, aroma, acidity, flavour, shelflife and presumed nutritional values of the fruit are important in ensuring repeat buys for sustained repeat purchase (Hewett, 2006; Shewfelt, 2009).

The physical appearance of the peel is especially important in the highly competitive export market. Buyers of plantains and bananas in these premium market destinations require consistent supplies of uniform colored fruit with blemish-free peels. The ability to supply the market with cosmetically sound fruit becomes difficult due to various factors such as it short shelf life, which was mentioned before, insects and bacteria.

Market vendors who are actually part of the economy are force to increase the prize of banana because of its short shelf life. These vendors usually purchase their items (banana) in bulk and before the bananas become available to the public some actually ripes and becomes rotten eventually. Therefore in order to make a rational profit, as a consequence the cost of the fruit is increased. Although these vendors can avoid such implications, the cost and resources for them to take the proper precautionary is not easily accessible.

The short shelf life and constant handling of the fruit, exposes banana to bacteria and pathogen, which when combined together affect its quality. This not only affects the vendors but it can also affect costumers in such ways as being force to pay sky rocket prizes for bananas, which can possibly be avoided if careful implementation and preservation techniques are taken into consideration. Taking into perspective, the local implication, and the thought, however of just being able to export standardise quality of banana is just spectacular and it might even contribute positively to the country's gross domestic earnings. The fact is that many bananas are produced but not many are being exported, and even so many are not even available for the public utilisation especially those bananas grown through commercial purposes.

The synthesis of ethylene gas by the fruit has tremendous effect on its shelf life by causing early maturation of the fruit when it comes to storage or during shipment. Ethylene is a hormone that initiates a whole series of cascade reaction that result in ripening of the fruit. Some of these cascades of reactions might include reaction such as the conversion of pectin in fruits, conversion of starch to glucose and the change in fruit colour and texture. These reactions however are catalyzed by specific enzyme but the ethylene hormone is the causative factor for these reactions to proceed.

For the particular ethylene hormone to carry its function efficiently it is required that the fruit be maintain well within an oxygenated environment. Therefore theoretically if we are able to modify the atmosphere thus lowering the content of the air we might be able to delay the ripening of the particular fruit.

Like other fruits, bananas remain alive after being picked and they actually continue to respire. This means they take in oxygen and release carbon dioxide. The more the banana breathes the faster it ripens and then rots. Bananas ripen more quickly than most fruit because they don't naturally slow the respiration after being picked; in fact it speeds up, giving bananas their notoriously short shelf life. The banana's pulp releases a chemical that boosts respiration, and the pulp converts into the sugars that produce that sweet, banana taste. As respiration continues, however, the process speeds up, and bananas become unpleasantly sweet and mushy. Bacteria on the banana skin start to thrive and cause the banana to rot.

Over the past years various methods had been postulated about ways to extend the shelf life of the climacteric fruit. These methods that are being put forward are very expensive to implement and are mostly suitable for large scale company. Therefore third world countries such as Guyana will not have a chance of earning a plausible economical profit if there were ever to implement such preservation techniques. Even if local farmers consider those preservation techniques they lack the incentives to do so on a large scale basis due to the position and quality of the economy (R.persaud)

They are ways of altering or modifying the atmosphere and treating fruits with gibberelic acid to prolong the shelf life of the fruit (Hiba Elmukhtar Osman et al). Giberrelic acid is a growth hormone of plants that is theorise by the authors to delay ripening and senescence of the fruit. Each of the fruits were treated separately with gibberellic acid, where gibberelic acid was applied to the tips of the fruit of one setup and another setup where the whole fruits were applied with gibberrelic acid and the data collected separately. The other set of fruits were placed in a modified condition similar to that of a partial vacuum; however boxes were lined with seal or perforated with polyethylene bags. Although there are a lot of publications as it relates to the use of gibberelic acid to delay fruit ripening and to promote firmness, the use of gibbereilic acid has been found to delay fruit maturity only 3-5days (Drake et al, 1978, Facteau, 1989, Looney Lidster, 1980, Proebsting et al 1973). The extraction or the isolation of the gibberelic acid is a very complex procedure (E.E.H Wolf and J.T. Loubser, purification, pg 58) that is very lengthy, costly and time consuming. Therefore to spend that much time and cost towards an such initiative preservatory method that would only be extending the shelf life of the fruit for about three or four days in advance is not financially favourable. Another method or experiment that was published used potassium permanganate (KMnO4) to control the ethylene concentration within the air of the particular environment that the fruits would be exposed to. According to the experiment done by the D.F.P Silva et al from the University of Federal Vicosa (UFV) using papaya fruit, they were able demonstrate that the KMnO4 is able to oxidize via reaction with the ethylene produced by the fruit to release carbon dioxide and water. The particular paper written by the authors rectify theoretically that the papaya treated with KMnO4 within an enclosed bag showed an reduction in respiration, evident by the low carbon dioxide concentration within the bag, However depending on the concentration of the KMnO4 used, the carbon dioxide formed by the ethylene reaction will react with the water to form carbonic acid overtime which coherently affect the quality of the fruit. the results were a follow up observation obtained for the preservation of the papaya fruit; the particular method was able to extend the shelf life of upto about 25days. Contrary to the particular paper written by the authors that showed that the KMnO4 is able to decrease the shelf of the fruit, however it has proven that this particular experiment can be invaluable to the shelf life of the fruit, because according to experiment done base on the reaction between KMnO4 and ethylene these publications fail to make reference of the extensive use and the effect of the KMnO4 over time. In some instances, however KMnO4 has found to be effective in terms of reducing senescence and the ripening of the fruit, but on the other hand the use and obtaining KMnO4 has found to be very expensive (Joshua Duvauchelle). Most likely the use of KMnO4 requires a medium before it can work, this might be the use of a charcoal like medium mentioned by some publications (S.K. Clenedennen et al).

The ethylene antagonist 1-methylcyclopropene (1-MCP) has been extensively applied and studied to extend the green life or shelf life of bananas (Macnish et al. 1997, 2000; Golding et al. 1998; Jiang et al. 1999; Harris et al. 2000). Despite good results of 1-McP delaying fruit softening, soluble solids accumulation and colour development, an uneven ripening of peel following treatment with 1-MCP has been reported (Golding et al. 1998; Harris et al. 2000). This uneven ripening of the peel appears when, after ethylene treatment, 1-McP is applied to bananas which have not completely lost their green peel colour, and results in a dull-grey appearance. Moreover, these symptoms are often coupled with areas on the peel that remain green, similar to blotchy ripening of tomatoes. It has been observed on banana fruit treated at ripening stage 2.

(Dole Ripening Guide) with ethylene, before or after 1-McP treatment, that respiration was completely

inhibited by 1-McP whereas ethylene was slightly affected and this response affected, at a different level, quality characteristics of bananas (De Martino et al. 2004). In particular, yellow colour appearance was completely delayed whenever the 1-McP treatment was performed. Similar results, but with a lower

response, have been obtained treating bananas with 1-McP at a more advanced ripening stage. Moreover, in banana during ripening there is a dramatic increase in acetaldehyde, ethanol and alcohol dehydrogenase (ADH) activity which probably contributes both to the removal of astringency and to the development of aroma volatiles (Hyodo et al. 1983; Pesis et al. 2001).thus, the hypothesis that the uneven peel ripening during these earlier stages of ripening following 1-McP treatment could be related to an imbalance in the respiration pattern with the accumulation of volatile compounds such as ethanol and acetaldehyde which affect peel de-greening, has been proposed.

To verify this hypothesis, other treatments following ethylene treatment were performed to examine similar development of peel symptoms. One of the most known disorders of banana is chilling injury (CI) which induces a dull-grey appearance of the peel very similar to that observed for 1-McP treatment (Pantastico et al. 1967; Ratule et al. 2006). In addition, nitrogen treatment was shown to prolong banana shelf life (Wills et al. 1990; Klieber et al. 2002), however the anaerobic conditions did cause some peel discoloration, where the visual symptoms were similar to those observed in 1-McP treated fruit. Thus, a nitrogen treatment was also assessed in this experiment. Ethanol and acetaldehyde has been seen to affect ripening of different fruits (Pesis 2005). Response of fruits to such anaerobic metabolites varies with species. Bananas treated with ethanol and acetaldehyde delayed ripening only for the latter compound but peel discoloration was observed (Hewage et al. 1995).

In reference to some of the methods that have been implemented to extend the shelf life of the fruit a less complicated, cheap and highly convenience method had been postulate to extend the shelf life of the fruit. This method solely relies on the use of polyethylene bags whereby we will be able to alter or modify the environment within the bag in order to create a partial vacuum that will be able to restrict the ethylene concentration in the bags and at the same time seeks to prolong the shelf life of the fruit. The ethylene concentration will become lower as a consequence due to the removal or reduction of the medium that is air (oxygen), which is required as a reactant for the metabolism of ethylene. Being able to restrict the gaseous concentration we should be able at a limited level to inhibit some amount of fruit ripening thus delaying the decay process and as such be able to extend the shelf life of the fruit.

Once the bananas are place in a well oxygenated environment they make use of the oxygen around them and release carbon dioxide through respiration, which leads to the production of ethylene.

Materials

Bananas

A green bunch of bananas was picked from a sucker tree located in the county of Essequibo coast, while two large hands of banana of the following types, cayenne and apple bananas were bought from the Bourda market. The green bunch of bananas comprised of the commonly called Parika Fig bananas. The cayenne was much longer in length as compared to both the Parika fig and apple bananas. The bunch of bananas was harvested at their full unripe stage; they were also selected base on green colouration and blemish free appearance. The bananas bought from the market were also selected base on these criteria. Question was forwarded to the vendor base on their shelf life and duration from the time bananas were picked. This was done, however to make a much precise judgement when selecting the bananas and to limit the number of sources of error.

Polyethylene bags

The non perforated light density and Medium density polyethylene bags were used for the experiment, the medium density polyethylene was about 4 to 5 feet in length and the low density polyethylene bags had a length of about 1.5 to 2 feet. As the name suggest the bags differ in their textures. About nine high density polyethylene and three light density polyethylene were used for the duration of the project. The bags were carefully inspected to make sure that they were not any holes that will contribute to the free flow of air in and out of the bag after a vacuum would be created using the rotary pump.

Rotary Pump

A rotary was obtained from the chemistry department and the experimental set up was done in the particular chemistry lab located at the bottom floor of the natural sciences building. The pump serves as a means of removing most of the air from the polyethylene bags.

Duct Tape

Each of the polyethylene bags containing bananas was wrapped with the particular tape towards the opening end.

Methodology

The project was divided into two parts comprising namely of a preliminary and the actual project itself. The green bunch of bananas were cut base on hands, therefore a hand was obtained from a common segment on the particular bunch. This was done to illuminate any bias, which may have any influence on the final results. Five hands were obtained after the bunch was cutted, each hand was further cut to give a total of two bananas sets. Therefore taken into consideration the five initial hands of banana, the total number of banana set was ten after further cutting.

The two sets of bananas that were derived from each hand were carefully handle and observe not to be mixed up with the other banana sets thus ensuring that there was little bias whatsoever. For the two bananas set that were derived from one banana hand, set up was done according to the following two treatments: 1) control, where one banana set would remain outside therefore there wasn't any alteration of the environment where the bananas set would be place. 2) Polyethylene bags with partial vacuum within, in this case a partial vacuum was created within the polyethylene bags facilitated by a rotary pump. The same previous treatments were assorted to the other banana sets that were derived from a common banana hand. The previous treatments were repeated respectively

Creating the partial vacuum within the bags

In order to remove the air from the bags the rotary pump was customised to facilitate the procedure of removing the air from the bags. A tube that would be inserted into the bags was run from the pump. The medium was placed within the polyethylene bags and the tube inserted, the neck of the bags was clamped using both hands while the air was being sucked out of the bag. An assistant helped to wrap around the duct tape at the end of the neck where the hands were, just below the end of the tube in the bag. The duct tape was tightly wrapped around the bags and this was done to restrict the free movement of air in and out of the bags. Even though the vacuum created was not a typical vacuum rather just a partial vacuum, it was substantial enough to conduct the experiment and establish grounds for the progress of the project.

This procedure was repeated for the other banana sets derived from the four remaining hands. Each of the banana sets that were derived from the same hand was given similar labels, which was necessary to differentiate them from another bananas derived from different hands. This was very essential when collecting data and making the necessary comparison. Therefore for the set up in experiment one, the respective labelled 1 was assigned to both the control and bananas that were placed within the modified atmospheric conditions (partial vacuum). This was similarly done for the other sets of bananas where 2, 3, 4 and 5 labels were assigned respectively.

The results were collected on a daily basis excepting on the weekends, therefore two days of collecting data were exempted from the week. Colour change was the only factor that was collected from the preliminary results and data was collected and analyse using the Chiquita colour scheme for bananas.

Chiquita is a common large scale enterprise that is responsible for the commercial sale of bananas, they usually monitor the progression and development of the bananas using the same mentioned colour scheme assigned with words, colour and numbers, where green-1, .......

Another set of experiment was conducted and this was base on the actual project itself, this involved the two large hands of bananas that were bought from the Bourda market. Each hand of banana was divided into three equal sets (comprising of equal numbers or fingers of bananas) as much as possible. This was necessary since each derived banana set was exposed to a different treatment. In the case with this experiment three different treatments had been allocated namely the control whereby this set of bananas remained outside, therefore no conditions was altered; the other banana set would be placed within polyethylene bags without a partial vacuum being created and the third banana set was placed in polyethylene bags with a partial vacuum created with the use of a rotary pump. The partial vacuum was created as was similarly done in the preliminary experiment set up whereby the rotary pump was customise in order to remove the air thus creating the partial vacuum. For the cayenne banana the high density polyethylene bags was used for the experiment while the light density polyethylene bags was used for the apple bananas. All the bags were tied that is the partial vacuum bags and the bags that had none of its air removed. This was done and stored within the biology laboratory storage room, located on the second floor of the natural sciences building and the data was collected everyday excepting on the weekends, therefore two days were exempted from the data collection. The duration of the project ran for a course of approximately one month.

Data collection and Analysis

The data is collected over a course of weeks with results taken every day and only once per day. The data was collected and analysed using the Chiquita brand color scheme that involved colours, words and with numerical value assigned, where green assign 1, green with yellow-2, more green than yellow-3, more yellow than green-4, yellow with green tips, all yellow-6, all yellow with brown spots-7.

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Any additional data such as colour, textures and physical appearance were noted in a special column titled observatory analysis and description. For the preliminary results common Chiquita color scheme was not used to analyse the data, however written observation or descriptive analysis was noted on a daily basis. For the ultimate results, those bananas set that had an uneven ripen of fingers; bracket with the number of bananas was used with the definitive of number to demonstrate the particular color observed. Therefore if two bananas from a particular banana set showed all green and another three from the same banana set showed green with trace of yellow then the particular data was analysed using the following: (2)1 and (3)2, with the bracket numerical value as an indication of the number of banana fingers and single figure besides the bracket as a representation of the color display for the bananas. Shelf life was then determined as the number of days taken by the fruit to progress from ripeness stage 1 to 7.

Since the data was collected over a successive time period the data was preferably analysed using a time series line graph. Since the data was collected daily this sort of data analysis would be suitable. The vertical line or y-axis included the scale of the various colour schemes, with the mean taken for the replicas in each banana set that had an uneven colour display among the banana finger in the same banana set.

Observation and Results

Preliminary Results: Banana used included the Parika Fig Banana

2012/05/14

1st sample observation of the bananas

The sample number of the banana

Banana set in vacuum conditions

Banana set in control

1

No visible signs of ripening. The bananas appeared bruised.

Appeared green and unchanged has those that were placed in the vacuum conditions.

2

No signs of ripening

All the bananas appeared green with the exceptions of one which showed signs of pre-ripening.

3

The bananas appeared green with no signs of ripening.

All the bananas appeared green

4

Green no signs of ripening

All of the bananas were green

5

The bananas all appeared green

green no signs of ripening

2012/05/15

2nd sample observation of the bananas

The sample number of the banana

Banana in vacuum in conditions

Banana control

1

The bananas showed no signs of change from the green state.

Also appeared unchanged, still green in appearance.

2

No change

One banana shows signs of yellowing on the scale two (2), while the other appears green.

3

Still appear green with no signs of ripening.

One shows signs of partial yellowing, other bunches of the bananas seem green.

4

Green with no signs of yellowing.

Bunch of bananas appeared like they wanted to begin yellowing showed small signs of tellowing

5

No signs of yellowing

No signs of yellowing for the control.

2012/05/16

3rd sample observation of the bananas

The sample number of the banana

Banana in vacuum in conditions

Banana control

1

No signs of ripening ripening appeared much bruised though maybe due to bacteria.

Bananas were partially yellow with much green while others showed signs of pre yellowing not much distinct though.

2

No signs of yellowing all appeared green.

One of the bananas was yellowed and started to rot. The other showed signs of partial yellowing at the tips. One was fully yellowed with some paches of green especially at the tips.

3

No signs of yellowing all appeared green.

Appeared much bruised, one of the bananas was fully yellowed with some form of rot the tip.

4

No signs of yellowing among the banana sets, still appeared green.

Bunches of bananas showed signs that they are ready to yellow. About four (4) of the bananas showed signs of rot.

5

No signs of yellowing. Banana appeared much bruised at the base of the fruit

Bunches appeared brighter in colorations. Signs pf pre-yellowing.

2012/05/17

4th sample observation of the bananas

The sample number of the banana

Banana in vacuum in conditions

Banana control

1

No Signs of ripening

Two of the bananas were yellow with partial visible signs of some green.

2

No signs yellowing

Some of the bananas appeared rotten which was evident by browning of the fruit. Some showed signs of yellowing with the others appearing green

3

No signs of yellowing

One banana appeared rotten with two appearing with some form of trace yellow.

4

No signs of yellowing

One of the bananas appeared more yellow than green. With small patch of green being expressed at the tips.

5

No signs of yellowing

No signs of yellowing from the younger bunch of bananas.

N.B Values in the bracket are representative of the number of bananas.

Ultimate Results

Wednesday 2012/06/20

Sample taken for the type of banana (Apple Banana) Musa sapientum

Treatment type for the bananas

Colour scheme

Observatory analysis or description

Control

1

All of the bananas were still green.

Plastic treatment without the vacuum

1

Bananas were all green. Water droplets were seen in the bag, which are positive signs for respiration.

Vacuum treatment

1

Bananas were all green will signs of respiration accounted for evidence by the presence of water droplets in the bag

Sample taken for the type of bananas (Cayenne Bananas) Musa acuminata

Treatment type for the bananas

Colour scheme

Observatory analysis or description

Control

1

Still green

Plastic treatment without the vacuum

1

Bananas still green

Plastic with vacuum conditions

1

Bananas still green

Thursday 2012/06/21

Sample taken for the type of bananas (apple bananas) Musa sapientum

Treatment for the bananas

Colour scheme

Observatory analysis or description

Control

1

Still appeared green, spots of brightness seen.

Plastic

1

Bananas still appeared green

Vacuum

1

Bananas were all green.

Sample taken for the taken for the type of bananas (Cayenne Bananas) Musa acuminata

Treatment for the bananas

Colour scheme

Observatory analysis or description

Control

1

Still green with signs of small yellowing.

Plastic

1

Still green

Vacuum

1

Still green

Friday 2012/05/25

Sample taken for the type of bananas (apple bananas) Musa sapientum

Treatment for the bananas

Colour scheme

Observatory analysis or description

Control

(1)2

(2)1

One of the bananas has small areas that were show signs of initial yellowing. The remaining set of the bananas still appeared green.

Plastic

1

Bananas were still green

Vacuum

1

Bananas were still green

Sample taken for the type of bananas (Cayenne bananas) Musa acuminata

Treatment for the bananas

Colour scheme

Observatory analysis or description

Control

1

Bananas still appeared green

Plastic

1

All the bananas appeared green.

Vacuum

1

All the bananas appeared green

Monday 2012/05/28

Sample taken for the type of banana (apple banana) Musa sapientum

Treatment for the bananas

Colour scheme

Observatory analysis or description

control

7

Banana was fully ripe or yellow in appearance.

plastic

(3)3

(1)4

Three of the bananas was green in appearance while the remaining banana was more yellow than green in appearance.

Vacuum

1

Still green no signs of ripening

Sample taken for the type of banana (cayenne banana) Musa acuminata

Treatment for the bananas

Colour scheme

Observatory analysis or description

Control

(1)2

(3)1

One of the bananas was green with small trace of yellow. The banana was soft to the touch compared to the other bananas that still were green in appearance at this stage

Plastic

1

Bananas within the plastic were still green.

Vacuum

1

Bananas were still green.

Tuesday 2012/05/29

Sample taken for the type of banana (Apple bananas) Musa sapientum

Treatment for the bananas

Colour scheme

Observatory analysis or description

Control

7

The bananas were Yellow with brown spots

Plastic

5

Yellow with green tips. Dark spots were visible close to the tips of the fruit.

Vacuum

2

Bananas still green with some showing signs trace of yellow

Sample taken for the type of banana (Cayenne Banana) Musa acuminata

Treatment for the bananas

Colour scheme

Observatory analysis or description

Control

(1)5

(3)2

One fully yellow with some form of greening at the tips of the fruit. Three of the fruits including the fully yellow bananas were soft to the touch. The remaining banana was fairly firm when touched.

Plastic

1

Bananas still green but are much softer compared to the bananas in the partial vacuum treatment.

Vacuum treatment

1

Bananas were still green. Less water droplets were seen when compared with those bananas in the plastic without vacuum treatment.

Wednesday 2012/05/30

Sample taken for the type of banana (apple banana) Musa sapientum

Treatment for the bananas

Colour scheme

Observatory analysis or description

Control

7

All the bananas were fully yellowed with signs of brown spots

Plastic

7

Fully yellowed with a few browns on the bananas.

Vacuum

4

More green than yellow and not much brown spots

Sample taken for the type of banana (cayenne banana) Musa acuminate

Treatment for the bananas

Colour scheme

Observatory analysis or description

Control

7

One of the bananas was fully yellow with a lot of brown spots. The other bananas were more yellow than green with much distinct greening at the tips. These particular also had the present of brown spots but a fewer compared to the fully ripe bananas.

Plastic

1

All the bananas were still green and were soft to the touch. One of the bananas had a split on the surface of the fruit. No clear indication of initial ripening apart from the soft texture

Vacuum

1

All of the bananas were still green with, no signs of brown sex and still hard to the touch.

Thursday 2012/05/31

Sample taken for the type of banana (Apple Banana) Musa sapientum

Treatment for the bananas

Colour scheme

Observatory analysis or description

Control

--------

All the bananas rotted

Plastic

7

All bananas were fully yellow with brown spots

Vacuum

5

Bananas were more yellow than green with only small patches of green.

Sample taken for the type of banana (Cayenne Banana) Musa acuminate

Treatment for the bananas

Colour scheme

Observatory analysis or description

Control

7

Three of the bananas were fully yellow with brown spots. The other banana was yellow with small patch of green at the tips.

Plastic

(1)2

(3)1

The split banana was partially yellow while the other bananas were still green in appearance and soft to the touch as well.

Vacuum

1

The bananas were still green in appearance but were softer to the touch compared to results from the previous days.

Friday 2012/06/01

Sample taken for the type of banana (Apple Banana) Musa sapientum

Treatment for the bananas

Observatory analysis or description

Control

All of the bananas were rotten

Plastic

Vacuum

Sample taken for the type of banana (Cayenne Banana) Musa acuminate

Treatment for the bananas

Colour scheme

Observatory analysis or description

Control

7

Plastic

2

All the bananas were soft to the touch.

Vacuum

1

Some of the bananas were fairly soft while some felt hard to the touch.

Discussion

Figure Showing the Cayenne Banana set with different treatment exposure and the graph plotted with the mean deviation of each banana set in separate treatment against the day results were taken.

The polyethylene bags that a partial vacuum created within had the greatest significant on extending the shelf life of the fruit. From the graph it is clear to see that the vacuum bags had the greatest extension of shelf life for the fruit. the polyethylene bags only had the second most significance of extending the fruit shelf life this was because the bag was tied as well and the flow of air within the bag might have been restricted but compared to the concentration of air to that in the partial vacuum, the polyethylene bags had the highest concentration of air and thus the air in the particular non vacuum polyethylene bags might have been more.

From the implacable understanding it is clearly seen that yangs work at play here, whereby the step to produce ethylene (yangs cycle) was altered because of the lower oxygen concentration in the bags. Lack of oxygen or lower oxygen will inhibit the yang cycle leading to a null or lower production of ethylene. In the treatment plastic and vacuum containing the particular set, the collection of data was stopped before any significant color change occur to yellow because the fruit in the respective polyethylene bags were very soft, which started one day prior to the end of data collection. The bananas set expose to treatments, plastic only and vacuum in plastic at the end of data were very soft and mushy, which might have resulted from respiration occurring in the fruits.

The banana in the polyethylene bags had no colour change until about the last day of data collection where a significant color change was observed, therefore this change occurred from all green to green with trace of yellow. The bananas within the partial vacuum had no significant color change but due to the texture and mushiness of the fruit, the shelf life was calculated by subtracting the days when the softness of the began to occur. Therefore for the banana set in the treatment partial vacuum the total shelf life from the point the fruits were expose to desire conditions was found to be 7days. The banana in the control had a shelf life of 6 days. Therefore the partial vacuum condition was able to extend the life of the fruit as compared to the control by approximately 2 days. This value was substantial since it prove the hypothesis was proven, and thus with the proper incentive and the advancement of creating a better vacuum conditions there should be addition of days where the shelf life of the fruit should be increase.

The banana in the polyethylene bags showed the same number of days of shelf life as compared to those bananas set in the partial vacuum but with an apparent color change, which started at around the 7th day of data collection.

Figure showing the apple Banana set with different treatment exposure and the graph plotted with the mean deviation of each banana set in separate treatment against the day results were taken

The banana set in the control had the shortest shelf life as is show by the graph, the banana set in the polyethylene bag had the second shortest and those in the vacuum polyethylene bags the longest shelf life among the three treatments. During ripening of the fruits the moisture content of the fruit increased, which was especially evident in the polyethylene bags both with a partial vacuum and non partial vacuum created within. This increased in moisture content might have been as a result of transpiration by the fruits evident by the number of water droplets in the bag.

The banana set in the control treatment had a shelf life of 4 days total, those within the polyethylene bag had a total shelf life of 6 days while the banana set in the partial vacuum had a total shelf life of 8 days. Therefore compared to the banana set in the control the partial vacuum was able to extend the shelf life of the fruit by 4 days. The peel changed from green to yellow as the chlorophyll was degraded to unmask the yellow carotenoids (Gray et al., 2004) hence influencing the lightness of the peel positively on ripening.

From the graph if we examine the order of the shelf life for the various treatments it is possible to see that those bananas in the polyethylene bags lies between control and partial vacuum treatments. This might have occurred as a consequence of a higher concentration of air as compared to that in the vacuum and the restriction of free flow of air in and out of the bag. As the air is used up for respiration and the conversion of reactants to ethylene the total concentration of air in the bag is depleting. When the air reaches below a particular threshold the rate of ethylene biosynthesis might be lower as result. This theoretical analysis explains the shelf life of the non vacuumed polyethylene bags exhibited by the banana set in this particular treatment as was shown in the graph.

Figure showing different types banana set that served as the control and there ripening period plotted against days.

Figure showing different types of banana sets that was placed in polyethylene bags only and there ripening period plotted against days

Figure showing different types of banana sets that was placed in polyethylene bags only and there ripening period plotted against days

From the graph it is clear to see that in the control the apple banana had the shortest shelf life as compared to that of the cayenne bananas. The same was observed for the successive treatments where cayenne bananas showed the greatest significance in of extended shelf life. Comparison between the various types of banana was done as was shown in the graphs above. Each type of banana that was exposed to the similar treatment was compared using separate graphs. Although these analytical graphs had no significance on the project itself, there were very useful and serve as reference to make side by side comparison between the various types of banana base on the shelf life and ripening period. What made these graphs less significant to the project was the fact that they were derived from different type of bananas and the fact that they weren't picked at the same time. Different types of banana have different stages of ripening and thus there implications on the shelf life of the fruits might have been altered and thus impose drastically on the final outcome of the data collection.

Even the project, however could have been manipulated using one type of fruit that came from the same hand and place the different banana set, that would have been derived from the particular type of banana into separate polyethylene types of bags.

Conclusion

The study has shown that vacuumed polyethylene bags may be used in commercial banana in Guyana to produce high quality fruits and extend the shelf life. The physical and biochemical properties of the banana fruits were not adversely affected this method. Due to prolong periods of ripening the banana exhibited high moisture content, which caused it to appeared to soft and mushy extremely evident as in the case with the cayenne bananas. With the construction of a highly functional vacuum and lower temperature it would be possible to lower the amount of moisture content released and synthesise by the fruit.

Also, the fruits within the vacuumed bags were more visually appealing as they were clean and had minimal bruises compared to those fruits that served as the control.

However, the use of vacuumed polyethylene bags should be coupled with proper pre-harvest handling and techniques procedures to ensure that the clean, visually appealing fruits are not bruised during the postharvest period.

Such fruits could also be targeted for the export market where they may fetch better prices as the consumer appreciates the visually appealing fruits and are willing to pay more for such fruits. the cost of using polyethylene bags to create partial vacuum as shown to be very profitable since it can be bought in packs, however the ease of accessing these bags in Guyana have to be major problem especially the medium density polyethylene bags, which has shown to be more effective in extending the shelf of the fruit.

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