PRESERVATION OF NUTS:

SCIENCE & TECHNOLGY

BY: PRATHAMESH KUDALKAR 13FET1011

GUIDE: PROF. SMITA LELE

INTRODUCTIONA nut is a fruit composed of a hard shell and a seed, which is generally edible.Most of the products we call nuts are not nuts in botanical sense.Tree nuts have become increasingly popular as a component of healthy diets throughout the world.Nuts are associated with a reduction in the risk of heart disease and have been shown to contain high levels of antioxidants.The United States leads the world in tree nut production with 2.4 million tons of in-shell nuts produced during 2010.Due to their exclusivity, nuts are highly valued agricultural products. Almonds Walnuts Cashew Peanut

Price/kg (Rs) 1200-1400 1400-2000 1100-1400 150-200

STRUCTURE OF NUTS

COMPOSITION OF NUTSAmount/100g Almonds Cashew Walnut Peanut

Energy (kcal) 576 553 654 570Total Fat (g) 49 44 65.2 48 Saturated Fat (g) 3.7 7.8 6.1 7 PUFA (g) 12 7.8 47 24 MUFA (g) 31 23.8 9 16Carbohydrates (g) 22 30 13.8 21 Dietary Fiber (g) 12 3.3 6.7 9Protein (g) 21 18.2 15.2 25Calcium (mg) 264 37 98 62Magnesium (mg) 268 292 158 184Iron (mg) 3.72 6.68 2.91 2Water 4.7 5.2 4.07 4.26

*All values from USDA Database

FACTORS RESPONIBLE FOR SPOILAGE IN NUTS

Spoilage of Nuts

Pests

Microbial growth and

toxin production

Lipid Oxidati

on

PESTSA destructive insect or other animal that

attacks crops, food, livestock, etc. is termed as a pest.

Field Pests Storage Pests

Don’t multiply during storage

Multiply during storage

Indianmeal moth

Almond moth

Excreta

Eggs

Larvae

Pin holes

Webbing

Beetles

Navel orangeworm

Codling moth

Borer Microorganisms

PESTSType Pest Nuts Adverse Effects References

Field Navel orangeworm

walnuts,almonds, pistachios

Deposit eggs, hatched larvae feed directly on nutmeats, increased aflatoxin levels

Campbell et al (2002),Johnson (2013)

Codling moth

walnuts Larvae bore into nuts and deposit feces

Strand (2003), Johnson (2013)

Peach twig borer

Almonds Larvae feeds on nutmeat

Strand (2002), Johnson (2013)

Storage

Indianmeal moth

All nuts Larvae can enter through cracks and holes as small as 0.4 mm, contamination of the product with silk, feces, cast skins, the insects themselves

Johnson (2013)

Almond moth

All nuts Feces, webbing Johnson (2013)

Red flour beetle

All nuts Feeding of larvae, cast skins, dead insects and feces.

Johnson (2013)

LIPID OXIDATION Mechanism

Initiation: It is the step in which free radicals react with Fatty acids to produce lipid radical. Reactive oxygen species are the most common initiators. Propagation: Lipid radical reacts with oxygen to form lipid peroxyl radical. This radical is also an unstable species that reacts with another free fatty acid, producing a different fatty acid radical and a lipid peroxide, or a cyclic peroxide if it had reacted with itself. 

Termination: The radical reaction stops when two radicals react and produce a non-radical species. 

• More than 80% lipids in nuts are unsaturated.

• Produces undesirable flavours and odours. Loss of nutrients

MICROBIAL SPOILAGE Mycotoxins

Mycotoxins are toxic secondary metabolites of filamentous fungi that can grow and produce such toxins on a wide range of food plants.Aflatoxins are the most toxic mycotoxins with hepatotoxic, mutagenic, teratogenic and carcinogenic effects on humans and animals.Aspergillus flavus is the most prominent microbe producing aflatoxins.Conditions: High relative humidity of around 97-99% and temperatures between 25-30 °CSource of contamination: SoilLimit: 15ppb

PathogensPathogens are the disease causing microorganisms.Don’t multiply on the surface of nuts but can survive.Cause nausea, vomiting, stomach cramps, diarrheaMicrobes: Salmonella enterica serovar Enteritidis PT 30, E. coliSource of contamination: SoilPrecaution: Pasteurization to ensure 4-log reduction of Salmonella enterica serovar Enteritidis PT 30

MICROBIAL SPOILAGE

Aspergillus species

All nuts Hepatotoxic aflatoxins, ephrotoxic ochratoxins. Permissible up to 10 μg/kg in EU.

Molyneux R. J. 2007; D. Clavel and C. Brabet. 2013

RhizopusPenicilllium

Salmonella enterica serovar Enteritidis PT 30

Almonds, Peanuts

Salmonellosis Danyluk, 2005

E. coli All nuts Nausea, vomiting, stomach cramps, diarrhea

Danyluk, 2005

Microbe Nuts Adverse Effects

Reference

METHODS OF PRESERVATION

Preservation of Nuts

Chemical

Non-thermal

Packaging &

Storage

Thermal

FUMIGATIONPropylene Oxide

• Flammable liquid• Boiling Point: 34.238 °C

Mode of action: Propylene Oxide targets the DNA and causes alkylation of DNA guanine, which results in breaking of DNA strandsEffective against: Pests, microbesResult: 5-log reduction of Salmonella

The U.S. Environmental Protection Agency (EPA) guidelines: (i) exposure temperature must not exceed 51.68°C(ii) exposure time shall be no more than 4 h(iii) PPO residue in the product shall not exceed 300 ppm.

Preheating of Nuts

48°C, 2 days

Vacuum 10 kPa

PPO Spraying

0.5 kg/cu.m

Aeration Cycles

Tempering

15-18°C, 5 days

Danyluk, 2005

EDIBLE COATINGS

Butylated hydroxyanisole (BHA)  Butylated hydroxytoluene (BHT)

BHA & BHT

E320 E321

BHA & BHT• Well known antioxidants• Found to cause Aspergillus

inhibition at in vitro level (Passone et al., 2007a).

• Suggested Mechanism: BHA affects the cell membrane by changing pH values and affecting transduction energy and substrate transport.

• Nut tested: In-pod Peanuts• Level: 1802 and 2204 μg g−1 of

BHA and BHT respectively• Results: After 5 months, close to 2-

log reduction in Penicillium spp. and 1-log reduction in Aspergillus spp. was observed.

(Passone et al., 2009)

EDIBLE COATINGSWhey Protein +

Tocopherol CMC + BHT

• Tested for: Peanuts• Effective Against: Oxidative

Rancidity• Principle: Films based on heat-

denatured whey-protein-isolate (WPI) have been found to be excellent oxygen barriers.

• Result: Accelerated shelf life studies estimated shelf life of 330 days at 25 °C

• Tested for: Almonds• Effective Against: Oxidative

Rancidity• Principle: BHT is well known

antioxidant. CMC has good film forming qualities and is a stabilizer.

• Result: Peroxide Value of coated sample was found to be half of the control sample

Constituent %CMC 0.5Glycerol 1.7BHT 0.2Distilled Water

97.6

Larrauri et al., (2016)

Lee and Krochta, (2002)

Constituent

% (w/w)

WPI 10Vitamin E 0.5

ORGANIC ACIDS Principle: Organic acids at high enough concentrations reduce the pH and bring about changes in protein configuration leading to cell lysis.

Shelling

Spraying

10% acid solution (1.6

ml/ 25g)

Air Drying2h, 25 °C

Storage

24 °C,3 days

Acetic Acid Citric Acid

• Safe• 5-log

reduction of Salmonella

Pao et al., (2006)

• High Cost• May have an

effect on product quality

STEAM PASTEURIZATIONSteam pasteurization is effective for reducing naturally occurring and pathogenic bacteria in foods (Nutsch et al. 1998)Effective against: Salmonella and other microbes.Advantages:Large amount of heat transferred to targeted foods when steam condenses, increasing the surface temperature promptly.It can effectively penetrate cavities, crevices and feather follicles that may provide protection for surface-attached micro-organisms.Process Conditions: Steam valve maintaining 143kPa constant pressureResult: 5-log reduction of Salmonella was achieved in 25s. No visual deterioration of quality. Increase in moisture content, secondary drying is needed. (Chang, 2010)

INFRARED PASTEURIZATIONAdvantages of Infrared heating:• High heat transfer

coefficients• Non-chemical method, no

flame• Easy temperature control

Lactic Acid Spray + NIREffective Against: Salmonella spp.Process Parameters: 10ml 2% Lactic Acid solution spray+ NIR (1300nm/ 500W)+ 23 rpm+ 5 min (80 °C)Results: 5-log reduction of Salmonella No effect on sensory qualities

(Ha and Kang, 2015)

INFRARED PASTEURIZATIONSequential Infrared and Hot Air

(SIRHA) Dry Roasting

Objective: Inactivate Salmonella Achieve roasted flavor

Process: Infrared Heating [6 min/(11000W/sq.m)]+ Hot Air Roasting(10s). Temperature: 140°C

Results: 5.8-log Salmonella reduction Desirable sensory characteristics 40% time reduction

Yang et al. 2010

RADIO FREQUENCY HEATING Introduction:Radio-frequency heating is the process of heating materials through the application of radio waves of high frequency—i.e., above 70,000 hertz Working: In a radio frequency heating system the RF generator creates an alternating electric field between two electrodes.The material to be heated is conveyed between the electrodes causing polar water molecules in the material to continuously reorient to face opposite electrodes.Friction resulting from this molecular movement causes the material to rapidly heat volumetrically.

RADIO FREQUENCY HEATINGAlmonds

Walnuts

Amount 1.7 kg 11 kgTo inactivate Salmone

llaPests

Pretreatment Soaking NoneFrequency 27 MHz 27.12

MHzTime 2-4 min 5 minTemperature 75°C 55 °CPower 6 kW 25 kWElectrode Gap

13cm 28cm

Hot Air Yes YesReference Gao et

al. ,2011S. Wang et al., 2007

Advantages of RF Heating Deeper penetration than MW Uniformity in heating

COLD PLASMA• Cold plasma is a collection of partially ionized gases

considered to be the fourth state of matter.• Cold plasma can be generated by passing gas between two

electrodes and product can either be placed between the electrodes to achieve contact with the plasma or the plasma can be moved to a site distant from the electrodes

Mechanism: Low temperature plasma generates highly reactive chemical species of molecular oxygen such as ozone, atomic oxygen, hydroxyl, nitric oxide and super oxide radicals as well as other free radicals which are the primary agents of antimicrobial action.

Experimental Results: A 30 s treatment at 30 kV and 2000 Hz reduced E. coli counts by almost 5 logs.

Advantages: No residues.

Disadvantages: Enhanced lipid oxidation, Nitrogen gas is not as effective as dry air.

Brendan A. Niemira ,(2012);Deng, (2007)

IRRADIATIONIrradiation is highly effective against pathogenic and spoilage organisms and insects.The term ‘food irradiation’ refers to exposure of food to one of three types of ionizing radiation: gamma rays, X- rays, or electron beams ( β particles).The penetration depth for electron beams is lower than that for gamma raysMode of Inactivation:High energy electromagnetic radiation can directly destroy the microorganism by damaging the DNA of the microorganism as well as the cell membrane thus disrupting cellular processes and causing cell death.Merits: Can inactivate microorganisms and pests at the same time.Demerits: Free radicals also react with large molecules such as proteins, carbohydrates, and pectins and can cause undesirable quality changes such as fat oxidation, pectin depolymerization, and development of off- flavors.

IRRADIATION

• D-value of Salmonella Enteritidis Phage Type PT 30 is around 1.25 kGy.

• 4-log reduction would require 5 kGy treatment which will make nuts sensorily unacceptable

Recommended Dosage: 1-1.5 kGy

D- value of most pests is around 0.2-0.3 kGy

2-3 log reduction is acceptable as a part of most quarantine treatments.

Dosage above 3 kGy rendered almonds unacceptable

Prakash, A, 2010;

PACKAGING & STORAGEVacuum Packaging• Most widely used

preservation technique.

• Objective is to reduce the oxygen exposure and inhibit oxidation and aerobes.

• Shrink film is used to have a tight fit.

• Retains quality.• Shelf life: > 3 yrs

MAP• Modifying the in

package atmosphere to reduce the respiration of nuts.

• Carbondioxide also has antimicrobial activity.

• Gas Composition:

Cooling• Reduces the rate of

breathing.

• Microbes are inactivated at low temperatures.

• • Shelf life at 4°C: > 1yr

• Shelf life at -18 °C: > 3 yrs

Gas %Nitrogen >80Carbondioxide

20

Oxygen < 0.5

PACKAGING & STORAGE

Oxygen Absorbers• Absorbs the headspace

oxygen.

• Reduce oxygen levels to less than 0.1%

• Shelf life: >12 months

• Eg: Silica Gel

Barrier Films• Polymer films with high

oxygen barrier properties extend the shelf life.

• Oxygen permeability should be lesser than 10 cc/sq.m.

• Eg: Polyvinylidiene chloride, Ethylene vinyl alcohol

Bulk Shipping & Storage• Vacuum packaging in

shrink wraps. • These packages are

shipped in enclosed wooden crates or metal containers.

• Stored in chambers with controlled relative humidity.

Methods for Preservation of NutsProcess

TypeTreatment Nuts Effective

AgainstFeatures References

Chemical Propylene Oxide Fumigation

Almonds, Walnuts

Salmonella, yeast, bacteria, mold, pests

Concentartion:0.5 kg/m3 for 4 h in Chamber, 5 days storage, Batch Process, <300 ppm.

Danyluk, 2005

Lactic Acid Spray

Almonds Salmonella Safe, 10ml 2% vol/vol, Combined with NIR heating (1300nm), Temperature rises to 80 degree C, 5min, No effect on sensory attributes.

Ha and Kang, 2015

Citric Acid Spray

Almonds Salmonella 1.6mL Citric Acid / 25g Almonds, Shelling and 3 sprayings, 5-log reduction of Salmonella

Pao et al., 2006

Whey Protein Edible Coating

Peanuts Oxidative rancidity 5% weight addition, Shelf life of 330 days at 25 degree Celcius.

Lee and Krochta, 2002

CMC+ BHT Edible Coating

Almonds Oxidative rancidity 0.5% CMC+ 0.02% BHT Solution followed by drying. PV half that of control sample after 120 days.

Larrauri et al., 2016

Phenolic Antioxidants (BHA, BHT)

Peanuts Aflatoxin accumulation Inhibits Aspergillus flavus and A. A. parasiticus

Passone et al., 2009

Thermal Dry Roasting Almonds, Peanuts, Cashew

Salmonella Most primitive method Sanders 2014; Yang et al., 2010

Oil Roasting Almonds, Peanuts, Cashew

Salmonella Oil roasting for 1.5 min at 150 C resulted in greater than a 6.0 log CFU/g reduction of Salmonella.

Sanders, 2014; Abd S. J. ,2012

Steam Almonds Salmonella 25s for 5-log reduction Chang, 2010Infrared Heating Almonds Salmonella 109 degree Celcius followed

by slow cooling for 1 hBari, 2009

Sequential infrared and hot air (SIRHA) roasting

Almonds Salmonella Effective than infrared heating Yang et al. 2010

RF heating Almonds,Walnuts

Pests, Microbes 25kW, 27Mhz, 5 min, 100% destruction of pests

S. Wang et al., 2007;Gao ,2011

Non- Thermal Electron beam irradiation

Cashew,Almonds

Pests 1 kGy dose. Lipid oxidation at high doses.

Singhal R. S., 2005; Mexis, 2009

Irradiation (Gamma rays)

Almonds, Walnuts Pest, Microbes 1 kGy dose. Lipid oxidation at high doses.

Prakash, A, 2010; Wilson-Kakashita, 1995

Cold Plasma Almonds Salmonella 30-sec treatment at 30 kV and 2000 Hz

Brendan A. Niemira ,2012; Deng, 2007

Packaging & Storage

Vacuum Packaging,Nitrogen Flushing, Packaging Films,MAP

Cashew, Almonds, Shelled Walnuts, Peanuts

Oxidative rancidity, Microbes < 0.5% Oxygen L.G.M. Gorris,1992; Mexis, 2009;Raquel P. F et al, 2014

CONCLUSIONSNuts are extremely valuable agricultural products with moderate risk of spoilage.Good Agricultural Practices (GAP) should be strictly implemented in fields.Only thermal treatments full-proof inactivation of microbes.Newer techniques like infrared heating should be practiced. Non-thermal treatments entail high cost.Spoilage due to oxidative rancidity can be minimized by proper packing and storage.Sprays of organic acids should be encouraged instead of chemical fumigants.Combination of techniques should be investigated.

REFERENCES CAMPBELL J F , MULLEN M A , and DOWDY A K ( 2002 ), ‘ Monitoring stored- product pests in food processing plants with pheromone trapping, contour mapping, and mark- recapture ’, J Econ Entomol , 95 , 1089 – 1101 .

STRAND L ( 2002 ), Integrated Pest Management for Almonds . Oakland, CA , University of California Agricultural and Natural Resources .

STRAND L ( 2003 ), Integrated Pest Management for Walnuts . Oakland, CA , University of California Agricultural and Natural Resources.

J. Johnson. 2013. Pest Control in Postharvest nuts. In: Improving the quality and safety of nuts. Linda Harris (ed.). Woodhead Publishing. 59-77

Danyluk, M. D., A. R. Uesugi, and L. J. Harris. 2005. Survival of Salmonella Enteritidis PT 30 on inoculated almonds after commercial fumigation with propylene oxide. J. Food Prot. 68:1613–1622.

Ha, J.-W., and D.-H. Kang. 2015. Combining lactic acid spray with NIR radiant heating to inactivate Salmonella enterica serovar Enteritidis on almond and pine nut kernels. Appl. Environ. Microbiol. DOI: 10.1128/AEM.00943-15.

Pao, S., A. Kalantari, and G. Huang. 2006. Utilizing acidic sprays for eliminating Salmonella enterica on raw almonds. J. Food Sci. 71:M14–M19.

Lee S.Y., and Krochta J.M. 2002. Accelerated Shelf Life Testing of Whey-Protein-Coated Peanuts Analyzed by Static Headspace Gas Chromatography. J. Agric. Food Chem. 2002, 50, 2022-2028

Passone et al. 2009. Postharvest control of peanut Aspergillus section Flavi populations by a formulation of food-grade antioxidants. International Journal of Food Microbiology 131: 211–217

T. H. Sanders and R. S. Calhoun. (2014). Effect of Oil and Dry Roasting of Peanuts at Various Temperatures and Times on Survival of Salmonella and Enterococcus faecium. Peanut Science: July 2014, Vol. 41, No. 2, pp. 65-71.

REFERENCES Abd, S. J., K. L. McCarthy, and L. J. Harris. 2012. Impact of storage time and temperature on thermal inactivation of Salmonella Enteritidis PT 30 on oil-roasted almonds. J. Food Sci. 71:M42–M47.

Yang, J., G. Bingol, Z. Pan, M. T. Brandl, T .H. McHugh, and H. Wang. 2010. Infrared heating for dry-roasting and pasteurization of almonds. J. Food Eng. 101: 273–280.

Chang, S.-S., A. R. Han, J. I. Reyes-De-Corcuera, J. R. Powers, and D.-H. Kang. 2010. Evaluation of steam pasteurization in controlling Salmonella serotype Enteritidis on raw almond surfaces. Lett. Appl. Microbiol. 50:393–398.

Bari, M. L., D. Nei, I. Sotome, I. Nishina, S. Isobe, and S. Kawamoto. 2009. Effectiveness of sanitizers, dry heat, hot water, and gas catalytic infrared heat treatments to inactivate Salmonella on almonds. Foodborne Path. Dis. 6:953–958.

S. Wang et al. 2007.Industrial-scale radio frequency treatments for insect control in walnuts I: Insect mortality and product quality Postharvest Biology and Technology 45 (2007) 247–253

S. Wang et al. 2007.Industrial-scale radio frequency treatments for insect control in walnuts I: Insect mortality and product quality Postharvest Biology and Technology 45 (2007) 247–253

Gao, M., J. Tang, R. Villa-Rojas, Y. Wang, and S. Wang. 2011. Pasteurization process development for controlling Salmonella in in-shell almonds using radio frequency energy. J. Food Eng. 104:299–306

Sajilata, M., & Singhal, R. (2006). Effect of irradiation and storage on the antioxidative activity of cashew nuts. Radiation Physics and Chemistry, 75, 297–300.

S.F. Mexis, M.G. Kontominas. 2009. Effect of g-irradiation on the physicochemical and sensory properties of cashew nuts (Anacardium occidentale L.). Food Science and Technology 42 (2009) 1501–1507

REFERENCES Prakash, A., F. T. Lim, C. Duong, F. Caporaso, and D. Foley. 2010. The effects of ionizing irradiation on Salmonella inoculated on almonds and changes in sensory properties. Radiat. Phys. Chem. 79:502–506.

Wilson-Kakashita, G., D. L. Geredes, and W. R. Hall. 1995. The effect of gamma irradiation on the quality of English walnuts (Juglans regia). Lebensm. Wiss. Technol. 28:17–20.

Brendan A. Niemira.(2012).Cold Plasma Reduction of Salmonella and Escherichia coli O157:H7 on Almonds Using Ambient Pressure Gases, Journal of Food Science, M171-M175

Deng, S., R. Ruan, C. K. Mok, G. Huang, X. Lin, and P. Chen. 2007. Inactivation of Escherichia coli on almonds using nonthermal plasma. J. Food Sci. 72(2):M62–M66.

L.G.M. Gorris and H.W. Peppelenbos. (1992). Modified Atmosphere and Vacuum Packaging to Extend the Shelf Life of Respiring Food Products. HortTechnology , 303-309

S.F. Mexis, A.V. Badeka, M.G. Kontominas. 2009. Quality evaluation of raw ground almond kernels (Prunus dulcis): Effect of active and modified atmosphere packaging, container oxygen barrier and storage conditions. Innovative Food Science and Emerging Technologies 10 (2009) 580–589

S.F. Mexis, A.V. Badeka, M.G. Kontominas. Effect of packaging and storage conditions on quality of shelled walnuts. Food Control 20 (2009) 743–751

Raquel P. F. Guiné, Cátia F. F. Almeida1, Paula M. R. Correia. 2014. Effect of Packaging and conservation conditions on some physical and chemical properties of almonds. Journal of Hygienic Engineering and Design

J. Johnson. 2013. Pest Control in Postharvest nuts. In: Improving the quality and safety of nuts. Linda Harris (ed.). Woodhead Publishing. 59-77

Molyneux R. J et al. (2007). Mycotoxins in edible tree nuts. International Journal of Food Microbiology 119 (2007) 72–78 D. Clavel and C. Brabet. (2013). Mycotoxin contamination of nuts. In: Improving the quality and safety of nuts. Linda Harris (ed.). Woodhead Publishing. 88-111