Peach is the most commonly eaten stone fruit which grows in the temperate regions of
the world. These are also among the most exported fruits in term of volume and value.
Peaches, being perishable and susceptible to microbial spoilage, have a short shelflife.
The goal of this study was to determine the effect of gamma irradiation on the
microbiological and organoleptic properties of peaches and secondly, to determine the
effects of irradiation on shelf-life of the fruit. The fruit (local variety, No.4), at proper
maturity stage was collected and irradiated with 0.25, 0.5, and 0.75kGy dose, stored
under refrigerated (4
o
C) conditions for a period of three weeks. Total viable count,
Gram negative Enterobacteriaceae count, Salmonella-Shigella count, yeast and mold
count, loss in weight and decay percentage was evaluated after 7, 14 and 21 days of
storage (4
o
C). Data obtained from microbiological and sensory evaluations of
irradiated peaches was compared with the observations obtained from unirradiated
(control) samples. Microbial evaluation of the fruits revealed the presence of
Salmonella sonnie on SS agar and non fermentor spp. on macConkey agar. Ten types
of yeasts were isolated on potato dextrose agar and analyzed microscopically. Studies
showed total bacterial, yeast and molds significantly decreased with increasing dose
level. The sensory evaluation of the fruits revealed that irradiation preserves the
texture and appearance of fruit. The gamma-irradiation dose of 0.75kGy proved to be
effective in reducing weight loss and significantly (p≤0.05) delaying the decaying of
the fruit by 7 days under refrigerated (4
o
C) conditions. Statistical studies were carried
out using Duncan’s multiple range test (DMRT) and means were separated by LSD at
5 %. It is hoped that this particular type of research will help in improving export
quality of peaches.
Table of Contents
1. Introduction
2. Literature Review
2.1. ORIGIN AND DISTRIBUTION:
2.2. THE PEACH PLANT:
2.3. NUTRITIONAL VALUE:
2.4. HEALTH BENEFITS:
2.5. PAKISTANI PEACHES:
2.6. PEACH VARIETIES:
2.6. PEACH EXPORT:
2.7. POSTHARVEST LOSS:
2.8. POST-HARVEST DISEASE OF PEACH:
2.9. FUNGAL PATHOGEN:
2.10. BACTERIAL PATHOGENS:
2.11. PEACH PESTS:
2.12. IMPORTANCE OF QUARANTINE TREATMENT:
2.13. CURRENT TREATMENTS:
2.14. GAMMA IRRADIATION AND FOOD SAFETY:
4.15. EFFECT OF GAMMA IRRADIATION ON PEACHES:
3. Materials and Methods
3.1. STUDY AREA:
3.2. SAMPLE COLLECTION:
3.3. SAMPLING:
3.4. ENUMERATION OF BACTERIAL LOAD:
3.4.1 NUTRIENT AGAR:
3.4.2. MACCONKEY AGAR:
3.4.3. SALMONELLA-SHIGELLA AGAR:
3.5. MEDIA PREPARATION FOR FUNGAL ANALYSIS:
3.5.1. POTATO DEXTROSE AGAR
3.6. INCUBATION:
3.7. COLONY COUNTING:
3.8. PURIFICATION OF CULTURE ISOLATES:
3.8.1. GRAM STAINING:
3.8.2. ENDOSPORE STAINING:
3.9. IDENTIFICATION OF FUNGAL SPECIES:
3.10. WEIGHT LOSS DETERMINATION:
3.11. DECAY PERCENTAGE:
3.12. DOSE OPTIMIZATION:
3.13. STATISTICAL ANALYSIS:
4. Results
4.1. TOTAL VIABLE COUNT:
4.2. Total gram negative, Enterobacteriaceae count:
4.3. Total gram negative lactose non-fermenting bacterial count:
4.4. ENTEROBACTERIACEAE IDENTIFICATION:
4.4.1. Through colony morphology:
4.4.2. THROUGH ANALYTICAL PROFILE INDEX 20 E
4.5. Total yeast and mold count:
4.6. PERCENTAGE DECAY ASSESMENT:
4.7. PERCENTAGE WEIGHT LOSS ASSESMENT:
4.8. SENSORY EVALUATION:
5. Discussions
Research Objectives and Themes
This study investigates the influence of gamma irradiation on the microbiological, sensory, and shelf-life characteristics of Pakistani peaches (Variety No. 4). The primary research question addresses whether specific doses of gamma radiation can effectively mitigate microbial spoilage and decay, thereby improving the fruit's export quality and storage duration under refrigerated conditions.
- Microbiological impact of gamma irradiation (0.25kGy, 0.5kGy, and 0.75kGy).
- Evaluation of shelf-life extension and reduction in decay percentage.
- Assessment of organoleptic properties, including texture, color, and microbial growth.
- Optimization of gamma radiation doses for commercial peach storage.
Excerpt from the Book
4.1. TOTAL VIABLE COUNT:
Morphological characteristics of the isolated bacteria are given in (table 4.2). Ten different types of bacterial species were seen on the nutrient agar during three weeks analysis. Most of these were medium sized, only one was small and two were large. Gram staining results showed that most of the isolated bacteria were Gram negative and were rod shaped (Bacilli), only one isolated bacteria was round (Cocci). Endospore staining showed that most of the isolated bacteria were non-endospore former. However, three isolates were endospore forming bacteria.
The effect of gamma irradiation on the total viable count of irradiated (0.25, 0.5, 0.75 kGy) and unirradiated samples is given in table (4.1) and fig. (4.1). Significant difference (p ≤0.05) was observed in the viable count of irradiated (0.25, 0.5, 0.75kGy) peaches as compared to unirradiated peaches. During the first week of analysis, total viable count (cfu/ml) observed on control sample, kept at 4oC was 3.10×105 ±0.63 which reduced significantly (p≤ 0.05) to 1.91×105 ±0.66 for the sample irradiated with 0.25 kGy dose as given (fig 4.2). After second week, viable count of control sample (3.10×105±0.63 cfu/ml) was significantly higher as compared to viable count (3.0×105 ±0.89 cfu/ml) of treated (0.25kGy) samples as shown in (fig. 4.3). Microbial analysis for the third week showed that control samples contain total viable count of 3.10×105 ±0.63 cfu/ml but it was not significantly different from total viable count (3.07×105 ±0.63 cfu/ml) for treated (0.25kGy) samples shown in (fig. 4.4). By comparing the viable count (cfu/ml) of treated (0.25kGy) and untreated samples, it was revealed that bacterial load was significantly (p≤0.05) lower in irradiated (0.25kGy) sample during first and second week, while no significant difference was observed in viable count (cfu/ml) after the three weeks of storage (4oC) as shown in table (4.1) and fig. (4.1).
Summary of Chapters
1. Introduction: Provides an overview of Pakistan's horticultural sector and the significance of peaches, highlighting the challenges of post-harvest losses and the potential for irradiation technology.
2. Literature Review: Details the origin, nutritional benefits, and current storage challenges of peaches, along with established methods for fungal and bacterial control.
3. Materials and Methods: Describes the experimental design, including sample collection, preparation of media, inoculation procedures, and statistical analysis methods used to assess irradiation effects.
4. Results: Presents the empirical findings on bacterial and yeast/mold counts, weight loss, decay percentages, and sensory characteristics observed across different irradiation doses.
5. Discussions: Interprets the experimental results in the context of food safety, post-harvest quality, and the potential for applying gamma irradiation to improve the export value of Pakistani peaches.
Keywords
Gamma irradiation, Peaches, Microbial load, Post-harvest loss, Shelf life, Food safety, Enterobacteriaceae, Salmonella sonnie, Fungal pathogens, Organoleptic properties, Export quality, Refrigerated storage, Duncan’s multiple range test, Bioburden reduction, Food preservation.
Frequently Asked Questions
What is the primary objective of this research?
The main goal is to determine the impact of gamma irradiation on the microbiological and organoleptic properties of peaches, and specifically how these doses can extend the fruit's shelf life for export purposes.
Which irradiation doses were tested on the peaches?
The researchers tested three specific gamma irradiation doses: 0.25 kGy, 0.5 kGy, and 0.75 kGy.
What scientific methods were used to evaluate microbial load?
The study utilized nutrient agar for total viable counts, MacConkey agar for Gram-negative Enterobacteriaceae, and Salmonella-Shigella agar for lactose non-fermenting bacteria, followed by morphological identification and API 20E testing.
What were the main findings regarding shelf life?
The study found that a gamma irradiation dose of 0.75 kGy was most effective in reducing weight loss and significantly delaying fruit decay by 7 days under refrigerated conditions.
Does irradiation negatively affect the quality of the peaches?
No, the sensory evaluation demonstrated that irradiation helps preserve the texture and appearance of the fruit compared to control samples, which softened and developed microbial growth faster.
What are the key themes covered in the study?
The key themes include the reduction of microbial bioburden, the effectiveness of gamma rays in controlling pathogenic decay, and the socio-economic potential of using these technologies to improve Pakistan's fruit export industry.
What specific bacteria were identified on the peach surfaces?
The analysis revealed the presence of Escherichia coli, Pseudomonas spp., and Shigella sonnie on the surfaces of the peaches.
Why is this research important for the Pakistani economy?
Given the high post-harvest losses of peaches in Pakistan, this research offers a cost-effective, scientific method to extend shelf life, thereby overcoming quarantine barriers and increasing the value of peach exports to global markets.
How were the statistical results validated?
Statistical validation was performed using Analysis of Variance (ANOVA), with means separated by Duncan’s multiple range test (DMRT) and significance set at p≤0.05.
What role does refrigerated storage play in this study?
Refrigerated storage at 4°C serves as the standard condition to simulate real-world storage environments, allowing researchers to measure the efficacy of irradiation in combination with temperature control over a three-week period.
- Quote paper
- Uzma Sarwar (Author), Mehwish Iqtedar (Author), Shagufta Naz (Author), 2014, Reduction of Bioburden by Optimizing Gamma Dose for Enhancing Export Value of Pakistani Peaches, Munich, GRIN Verlag, https://www.grin.com/document/289112
