Welcome

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Division of Vegetable Science ICAR-Indian Agricultural Research Institute

New Delhi-110012

Gajanan A.G.20594

Nano coatings : A novel approach for improving the shelf life of vegetables

India is the second largest producer of fruits (81.2 million

tonnes) and vegetables (162.1 million tonnes) in the world

(Horticulture data base, 2013)

But about 20 to 30% of the produce is lost annually due to lack

of adequate infrastructure and limited use of modern postharvest

technologies.

Fresh fruits and vegetables have short shelf life because of high

respiration rate, moisture content, bulky in nature and pathogen

attack.

Introduction

Critical factors involved in post harvest longevity

Maturity stage

Temperature

Water loss

Ethylene

Mechanical damage

Post harvest Diseases

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Methods to prolong shelf life

Shelf life

Pre cooling

Sorting, Grading

Post harvest

treatments

Packaging

MA/ CA Storage

Minimal Processing

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Nanotechnology

Nanotechnology ?..

“Design, Characterization, Production and application of structures, devices and systems by controlling the shape and size at the nanometer scale”.

Mousavi and Rezaei, 2011

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Father of NanotechnologyNobel Laureate – 1965Richard Feynman, Physicist, America

The term ‘ Nanotechnology’ Coined in

1974 by Norio Taniguchi of the Tokyo.

Properties of Nanoparticles Nano-scale materials show unusual physical, chemical and biological

properties. (Li et al., 2001)

Nanoparticles have large surface to volume ratio (Kumar et al., 2010)

Magical changes takes place at Nano level

Physical Surface area, conductivity, charge capacityChemical Reactivity

Mechanical strength

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Why we need Nanotechnology ???

To enhance the efficiency of available post harvest technologies

To reduce the economics of additives.

Ethylene biosynthesis inhibitors – AVG,AOA : Expensive and

Phytotoxic

Many chemicals which we are using may be soon banned due to

their environmental impact

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Nano-coating

Nano-sensors

Nano-packaging

Post harvest Management

Nano technologies- Vegetable crops

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COATINGS

Conventional coating

Nano coating Nano particle coating

Nanoemulsion coating

Zinc oxide:

Titanium dioxide:

Silver nanoparticles

• Antimicrobials

• Anti-ethylene agents

• Extend shelf life in carrot , Asparagus ( Jianshen, 2008 )

Antibacterial activity

E.coli contamination in foods

Nano particles - Few Examples

“NS release Ag+ (Lok et al., 2007), which has been reported to interact with cytoplasmic components and nucleic acids, to inhibit respiratory chain enzymes and to interfere with membrane permeability” Russell and Hugo,1994; Park et al., 2005

NANOEMULSION COATING“ Nanoemulsion consist of an lipid nano droplets (between 10 – 100 nm diameter ) dispersed in an aqueous solution and each oil droplet surrounded by surfactant molecules with unique physicochemical and functional characteristics” - Acosta (2009).

Functions of Nano coating

• Acts as a Natural layer to prevent moisture loss.

• Selectively allow controlled exchange of O2 & Co2

• Prevent the loss of important components- vitamins & minerals.

• May impart functional components: Antimicrobial; ethylene scavengers.

Effect of Alginate/ nano-Ag coating on microbial and physicochemical characteristic of shitake mushroom (lentinus edodes)

Jiang et al. (2013)

Food Chemistry

Case Study 1

Objectives To determine the effect of the alginate/nano-Ag coating

on the microbial and physicochemical characteristics of shiitake mushrooms, during storage at 4° C for 16 days.

Mushroom• Second most cultivated edible mushroom

• Why mushrooms are Highly Perishable Higher moisture content Lack epidermal structure. Extremely High respiration rate Higher PPO activity Susceptible to microbial spoilage

Pseudomonas tolaasii & Pseudomonas fluorescens yeasts - Candida sake

• Sodium alginate 1.5 %• AgNO3 (0.1 M) – Anti-microbial agent • NaBH4 (0.01 M) - • PVP (0.01 M) - • Glycerol – Plasticizer • Calcium chloride – Cross linkage.

Materials And Methods

(1) Control – simply Dissolved in water (2) Alginate coating(3) Alginate/nano-Ag coating

Treatment

Microbial count of nano-coated shitake mushrooms during storage

Modes of action of silver nanoparticles on bacteria

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Sukumaran Prabhu and Eldho K Poulose., 2012

Weight loss of nano-coated shitake mushrooms during storage

4.1%

< 2.5%

Firmness of nano-coated shitake mushrooms during storage

Loss of firmness is due to degradation of cell wall by bacterial enzymes and hence alginate acts as antibacterial compound

Reducing sugar (A), Total sugar (B), Total soluble solids (C), and Electrolyte leakage rate (D) in coated shitake mushroom

31.7

Coated sample maintain high membrane integrity hence less electrolyte leakage

16.5

Inference • Alginate/nano-Ag coating had beneficial effects on the physicochemical and physiological quality

compared to the control treatment.

• Weight loss, softening, and browning in the alginate/nano-Ag coated mushrooms were significantly inhibited after 16-days storage.

• Lower microbial counts, including mesophilic, psychrophilic, pseudomonad, and yeasts and moulds, in treated mushrooms during storage

• Reducing sugar (5.4%), total sugar (34.9%) for nanocoated mushrooms while total soluble solids (19.04% and electrolyte leakage rate (12.04%) for the alginate/nano-Ag coating comapred to control mushroom over 16 days storage.

• Slightly lower CO2 and higher O2 concentrations were recorded for nano-coated mushrooms indicating lower rate of respiration.

• Therefore, the alginate/nano-Ag coating could be applied for preservation of the shiitake mushroom to expand its shelf life and improve its preservation quality.

Antibacterial and physical effects of modified chitosan based-coating containing nanoemulsion of mandarin essential oil and three non-thermal treatments against Listeria innocua in green beans

Severino et al.(2014)

International Journal of Food Microbiology

Case Study 2

Objective- • To evaluate the antibacterial effects of modified chitosan-based coating

incorporating mandarin EO nanoemulsions in combination with three non-thermal treatments against Listeria innocua inoculated in green beans during storage at 4 °C.

Treatments-• Coating UV-C – 0.8 j/cm2• Ozone – 7ppm , 2.5 min γ-Ray 0.25 kGy

Materials & Methods:• Fresh green beans (Phaseolus vulgaris L.)• Stock cultures of L. innocua• Mandarin essential oil• Modified chitosan (MC, 3% N-palmitoyl chitosan, degree of palmitoylation

47%)

Parameters

• Microbial analysis• Relative Inactivation value• Texture• Colour

Relative inactivation value (RIV) for the different combined non-thermal treatments tested.

Pyrimidine dimers formation in DNA

RIV

control coating UV-c ozone Ƴ ray UV-C + coating Ozone + coating γ-Ray + coating0

1

2

3

4

5

6

7

8

9Day 1 2 5 8 12 15

Micr

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nt (L

og cf

u/g)

Effect of coating formulation in combination with non-thermal treatments on population of L. innocua on green beans samples during storage at 4 °C.

2.3

UV-C 2.83 log cfu reduction 1 st day & 5 log cfu during 15th day of storage

control coating UV-C Ozone Ƴ ray UV-C + coating Ozone + coating γ-Ray + coating0

100

200

300

400

500

600 Day 1 5 9 12 15

Firm

ness

(N)

Effect of coating formulation in combination with non-thermal treatments on firmness of green beans samples during storage at 4 °C.

in firmness is bcz PG,cellulae

Inference

• γ-irradiation and coating combined treatment exhibiting a strong synergistic antimicrobial effect.

• UV-C combined treatment with the bioactive coating, represent an effective approach to control the growth of L. innocua on vegetable foods.

Future prospects

• The efficiency and the economic benefits of applying various techniques in combination with nanotechnology needs to be evaluated in the different vegetable crops.

• Focused research is required in use of nanoparticles to improve the quality and the post harvest life of vegetables.

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Method of preparation