Contamination spoilage in fruits and vegetables pdf
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- Hygiene and Environmental Health Module: 8. Food Contamination and Spoilage
- Microbiological Spoilage of Fruits and Vegetables
- Microbiological Spoilage and Pathogens in Minimally Processed Refrigerated Fruits and Vegetables
- MICROBIAL SPOILAGE OF VEGETABLES AND ITS CONTROL MEASURES: A REVIEW
Hygiene and Environmental Health Module: 8. Food Contamination and Spoilage
Box , Doha, Qatar. This study aims at screening the post-purchasing shelf-life of four highly consumed fruits and vegetables and at identifying the fungal strains behind their spoilage in Qatar. Fruits and vegetables were collected from the market to study their post-purchasing shelf-life and to identify the fungal types involved in samples rotting. A total of 73 fungal isolates were isolated and identified, with the highest percentage of Penicillium Interestingly, many mycotoxins producing and diseases inducing fungi were identified in this study; this includes Rhizopus , Aspergillus , Penicillium , Alternaria , Fusarium , Cladosporium , Botrytis , Geotrichum , and Colletotrichum.
Statistical analysis shows that different fruits have significantly different shelf-life and different predispositions for spoilage. In many cases, a strong relationship was shown between the fungal types isolated and the country of origin of the fruit. Finally, the price of the commodity did not have a significant effect on its contamination level nor did the market from which the sample was purchased.
This indicates that the fruit displaying methods in Qatar do not affect their contamination level. The study is among the first reports about fungal types involved in fruits and vegetables rotting in Qatar and it highlights the strong link between spoiling fungi and their country of origin.
Microbiological food safety is a major economic and public health concern nowadays. According to the WHO, one in every 10 people become ill from consuming contaminated food each year, a trend that results in the death of , individuals annually WHO [ 1 ]. Food contaminants consist of physical agents, including pieces of metals or plastic, that enter food during the packaging stage of manufacture, as well as other chemical agents including heavy metals, pesticides, and, most importantly, microbes [ 2 , 3 ].
Even though freshly harvested vegetables and fruits are unavoidably contaminated with a variety of bacteria, fungi and other microorganisms. However, molds in general and mycotoxin producers in particular are the main cause of spoilage, especially in products that are refrigerated in open boxes [ 4 - 6 ].
Microorganisms, including bacteria and fungi, cause considerable economic losses by spoiling not only harvested fruits and vegetables but also crops in their fields.
The identification of such spoilage microorganisms is a crucial step toward controlling them. Some pathogenic strains specific to fruits are pathogenic to humans as well, especially those that produce toxins [ 5 , 7 ]. The metabolites of many such microorganisms are heat stable, which suggests that they remain in the food after heat processing and continue to cause toxicity. Once mycotoxins are formed, it is difficult to manage their quantities as they are stable under storage conditions and particularly insensitive to physical and chemical treatments.
Therefore, the best way to limit mycotoxin exposure is to stop them from forming in the first place [ 6 , 8 , 9 ]. Different spoilage-causing microorganisms have different nutrients requirements. Due to the variable composition of fruits and vegetables, it is important to determine the microbial hazards for each product separately.
Products of great concern include cucumbers and tomatoes, which are produced in large amounts in Qatar and are among the most highly consumed vegetables in the Middle East, as well as oranges and strawberries, which are used in great quantities for the production of fresh juices. Therefore, it is of significant concern to understand the spoiling agents behind their shelf-life termination [ 10 , 11 ]. In this study, samples of cucumber, tomato, strawberry, and orange were tested to determine their shelf life and to identify spoiling agents, if found.
Factors that affect the rate of fungal spoilage in the purchased samples were also analyzed. This study did not involve the use of live animals, and hence, ethical approval was not required. Samples were collected during four trips which took place between September and November All trips occurred on Saturday and samples were collected between At each market, a sample was collected per available type of cucumber, tomato, orange, and strawberry.
Samples were kept in the sterile bags and at a storage temperature approximating that of the supermarket until transferred to the laboratory the next day. The sample collection was kept individually in a sterile and empty Petri dish with a sample number identifier. When a sample began to exhibit fungal hyphae growth, it was removed from the incubator, at which point, the observer noted the day as the end of the home shelf-life of that particular sample.
Hyphae were subsequently collected using a sterilized needle and subcultures on potato dextrose agar PDA [ 12 ]. The number of spoiling spots on each sample was counted as a measure of contamination level. The process continued for 10 days, after which time, the experiment was completed. After 1 week of incubation, fungal isolates were identified using colonies and cell morphological features such as the thallus growth pattern, pigmentation, conidiophore, and conidial morphology [ 13 ].
Isolated fungi were identified using cotton blue in lactophenol stain. A drop of the stain was placed on a clean slide and a portion of the mycelia was placed on the stain using a sterilized needle and forceps. A coverslip was then placed on the wet mount and the slide was examined by a light microscope at various magnifications. The morphology and characteristics of the conidia and conidiophores were then used to classify the different types of fungus according to the standard taxonomic system [ 5 ].
Data were entered into the excel datasheet, pictures were taken of the fungi on the PDA agar, and pictures of each isolate under the microscope showing conidia and conidiophores were taken.
Out of the 90 samples, 51 Various types of fungus were isolated from different fruits. Table-1 shows the number of various fungal types isolated from each kind of fruit. A total of 73 fungal isolates were collected and identified, with the highest percentage of Penicillium Different mycotoxins producing fungi were isolated in the study.
Samples were collected from three large supermarkets in Doha. Chi-square test results of the comparison of the number of samples showing fungal growth among samples originated from different countries suggest that the country of origin has an effect on the contamination of commodities, although significance could not be proven, as more samples were needed to reach an adequate level of statistical power.
The effect of the country of origin can be observed when analyzing the results; for example, samples imported from the Netherlands were highly contaminated with Penicillium when compared to samples from other countries.
On the other hand, Penicillium is known to be more common in citrus fruits. However, the data in Table-1 do not demonstrate a significant difference between the number of Penicillium isolated from oranges and those isolated from the rest of the fruits, which might link Penicillium to the country of origin.
The data indicate also high concentrations of Cladosporium in samples originating specifically from Morocco. Interestingly, a total of 16 samples of cucumber were collected from Iran six samples , Qatar six samples , and Lebanon four samples. Out of the six locale samples, five were contaminated with Fusarium , suggesting that most Fusarium isolates are local in origin. Finally, it is worth mentioning that the rate of occurrence of Aspergillus and Rhizopus is particularly high in samples originated from the USA.
The various countries of origin of the samples were divided into countries categorized as having a developing economy and those with a developed economy as based on the Department of Economic and Social Affairs of the United Nations Secretariat.
The statistical results are likely to be biased by the fact that different fruits were exported from specific countries; for example, strawberries are more prone to spoilage than other fruits and, due to the nature of their skin, tend to be produced in developed nations. Number of samples originated from countries of different economy and their contamination frequency. The collected fruit samples ranged in price from items that were on promotion, to very expensive fruit types.
High and low price categories were created by considering fruits whose price was above or below the average for their category respectively. Chi-square test was computed to assess the effect of price category on spoilage rate. The test could not be conducted on strawberries because all samples were contaminated.
In the three categories of fruits tested, the data did not provide evidence that more expensive fruits are less contaminated or last longer. Instead, price variation may be a product of the quality of the commodity, rather than its home shelf-life.
Some fruits were found to be contaminated with more than one, but no more than three, types of fungi at once. Data were summarized in a boxplot and the results indicate that strawberry samples contain the greatest variety of fungi of all the fruits. This range of contamination is due to the nature of the skin of this fruit, which contains pouches that fungal spores get stuck within. It should be noted that strawberries were primarily contaminated with black molds, whose spores can easily be transmitted by air.
The cucumbers data demonstrate the existence of some outliers, but its median is at one fungal type per sample, whereas tomatoes showed high specificity in terms of fungal types and oranges did not have enough contaminated samples to be included Figure The P-P plot of the number of fungal types indicates that the number of fungal types per fruit sample follows a normal distribution data not shown.
Post hoc tests show that the main significant differences in the number of fungi are between cucumbers and oranges, oranges and strawberries, tomatoes and oranges, and tomatoes and strawberries. The level of contamination across different fruits was assessed based on the number of spots shown on each sample at the beginning of the rotting process.
Because each spot represents a spore, their number reflects the level of contamination. The levels were described as follows:. Figure-2 summarizes the contamination levels of each of the fruits. Strawberries exhibited the highest levels of fungi per fruit; again, this may result from the characteristics of its skin. Oranges exhibited a high level of contamination across However, the visibly bad condition of the fruit motivated us to take a swab culture from them on PDA, all of which demonstrated the growth of various fungi types.
The percentage of various fruits that have undetected, low, moderate, heavy, and swab detected contamination levels. The time taken by a fruit sample to rot will vary from 1 to more than 10 days. Based on the rotting speed, samples were divided as follows:.
Speed 4 samples: Long home shelf-life, the samples did not rot within the experiment time. Strawberries experienced the shortest home shelf-life, with all samples rotting within 3 days.
This period was followed shortly by cucumbers, of which Percentages of various fruits that have very short, short, moderate, and long home shelf-life. Fungi have always been a public health concern. In , a study conducted in Australia on packaged cheddar cheese showed that mold infections were tough to control as they were isolated from different equipment in the cheese factory, fungi were also isolated from the air, curd, and whey.
The most common fungi isolated from the packaged cheese samples were Cladosporium followed by Penicillium , which are our most commonly isolated fungi [ 14 ]. Similarly, in , Weidenborner determined the major source of contamination for pine nuts as Cladosporium. A total of 31 different species were isolated in the study, of which 16 were potentially toxigenic [ 15 ]. Recent studies regarding fungal contamination are conducted all over the world.
A total of isolates of fungi were recovered from nuts and dried fruits in the Washington D. Similarly, the most common isolated fungi type identified in a study by Tournas et al. In Brazil, a study investigating toxigenic fungi on dried fruits identified Aspergillus niger as the most common species from a sample of [ 17 ]. Both studies imply an affinity between Aspergillus and dried fruits. Similarly, a study of grapes conducted in Lebanon identified a high level of contamination with various strains of Aspergillus section Nigri.
In addition, tests of ochratoxin A OTA levels indicated low-level contamination of the isolates in
Microbiological Spoilage of Fruits and Vegetables
Most natural foods have a limited life. Perishable foods such as fish, meat, milk, bread, tomatoes and potatoes have a short life span. Other foods keep for a considerably longer time but decompose eventually. Once food has been harvested, gathered or slaughtered it begins to deteriorate until eventually it becomes unfit for consumption. This deterio-ration is known as decay and leads to food spoilage.
All food should be safe and free from contamination and spoilage at all points in its journey from its source until it reaches the consumers. However, food contamination is a serious public health problem in Ethiopia, resulting in foodborne diseases that affect many people every year. Hence, awareness of potential sources of food contamination is an important component of good nutrition and good health. In this study session we are going to concentrate on food contamination by microorganisms, chemicals and physical factors. Food may be contaminated by different microorganisms or by chemicals that can cause health problems for anyone who eats it. In Study Session 9 you will learn in detail about foodborne diseases.
Microbiological Spoilage and Pathogens in Minimally Processed Refrigerated Fruits and Vegetables
The focus of this chapter is to provide a general background on microbiological spoilage of fruit and vegetable products that are organized in three categories: fresh whole fruits and vegetables, fresh-cut fruits and vegetables, and fermented or acidified vegetable products. This chapter will address characteristics of spoilage microorganisms associated with each of these fruit and vegetable categories including spoilage mechanisms, spoilage defects, prevention and control of spoilage, and methods for detecting spoilage microorganisms. Fresh fruit and vegetable consumption increased by If US consumption patterns continue in this direction, total per capita consumption of fresh fruits and vegetables would surpass consumption of processed fruits and vegetables within the next decade.
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MICROBIAL SPOILAGE OF VEGETABLES AND ITS CONTROL MEASURES: A REVIEW
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