VACUUM FRYING TECHNOLOGY

Ranasalva N

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• Originated - Frying foods - Middle East - two millennia before

the birth of Jesus Christ

Introduction

Sautéing Shallow frying Deep frying

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• High pressure

• Atmospheric pressure

• Low pressure/Vacuum

Deep fat frying – carried out under

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Conv

Water

Cond

Penetrated oil

Surface oilCRUST

CORE

Mode of heat and mass transfer during deep fat frying (DFF)

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CRUST

CORE

Starch degradation

Non enzymatic browning

High temperaturesFrying oil thermal degradation

Beneficial compounds degradation

Water vaporization

Atmospheric conditionsFrying oil oxidation

Frying oil hydrolysis

Moisture loss

Oil uptake

Key structural components changes

Changes in product during DFF

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FOOD

OIL

UPT

AKE

DEH

YDRA

TIO

N

WATER

HYDROLYSIS

OXYGEN

OXIDATION

Cyclisation

Polymerization

HIGH TEMPERATURES (140 -200°C)

Isomerization

HEAT

Mono glyceridesDi glyceridesGlycerolFree fatty acids

AldehydesKetonesAcidsEpoxidesDimers - trimers

Hydro peroxides

Polar CompoundsFRYING OIL

Trans fatty acids

Cyclic Compounds

Dimers – trimersPolymers

Changes in oil during DFF

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?VACUUM FRYING

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Torricelli’s vacuum experiment in 1644. The level AB of mercury in both tubes C and D was equal, independent of the size of the additional volume E in tube D.

Democritus - 460 to 375 B.C. Bronze statue around 250 B.C., National Museum in Naples

History of vacuum science

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Otto von Guericke in 1672

Inventor of vacuum pump principle

Plenists Vs vacuists

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Non condensable gasNon condensable gas

VACUUM PUMP

Liquid condensate

Steam & Non condensable gas

SPINNER MOTOR

VACUUM FRYING CHAMBER

OIL HEATER

FRYING BASKET

CHILLER

LIFT ROD

Vacuum frying system

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1. Depressurization - 1.33 - 10 kPa

2. Frying and De-oiling – Heat and mass transfer occurs and

surface oil is removed

3. Pressurization – To atmospheric condition

4. Cooling – Product is cooled to room temperature and

stored

Stages of vacuum frying

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• Process Factor

– Pre frying

– Frying

– Post frying

• Product factor

• Oil factor

Factors affecting vacuum frying

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•Maltodextrin

•Drying

•NaCl2 soaking

•Citric acid

•Gelatinization

•Freezing

•Hydrocolloids

Pre frying (pretreatments)

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Paulo et al ,2008

14

Properties influences Properties influenced by

•Moisture content •Weight and moisture loss

•Pore structure •Oil absorption

•Pressure •Diameter shrinkage

•Thickness - expansion•Penetration pressure

Process temperature

April 18, 2023 15Temperature at different locations within the product during frying process (T =185°C, T=20°C)

Aman-Mohammad, 2009

Whole process (frying and cooling)

Cooling period

Process temperature

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• Oil absorption

• Browning Index

• Color

• Shrinkage

• Moisture content

Paulo et al ,2008

Process time

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• The frying is carried out from 1.33 kPa to 90 kPa

• Surface of food• Centre of the food• Head space of the chamber

Paulo et al ,2008

Process pressure

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DP – Depressurization; FR – Frying; PR – Pressurization; CL – Cooling; temperature of 120°C

Carla, 2010

CentreSurface

Head space

Pressure

Effects of process parameters

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Temperature of 130°C Temperature of 140°C

Carla, 2010

Effects of process parameters

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• Oil absorption - 80% absorbed during cooling

• Potato chips – 14% in core and 86% on the surface

• Pressure gradient between the product and atmosphere

cause intensive absorption of oil

• De-oiling – under vacuum - centrifuging speed 350 – 1200

rpm for 30 s to 30 min

(Garayo & Moreira, 2002, Moreira et al.,2009)

Post frying process

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• Size and shape - oil absorption increases thickness is reduced & product surface is increased

• Ripeness of fruits – suitable for high sugar products• Taste – Stronger taste of high concentration of taste

components• Surface roughness - Cells broken during cutting are a

privileged location for oil absorption• Solid content – high density product shows reduced oil

absorption• Moisture content

Product factors

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• Moisture content

• Oil content

• Microstructure

• Diameter - shrinkage

• Thickness - expansion

• Bulk density

• True density and

• Porosity

Changes in product

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Stages of Moisture loss

• Initial warm up period• Constant rate period• Falling rate period Moisture diffusion coefficient,

De,

(Broker et al., 1992)

Mdb - moisture content in (g/g solid), Mo - initial moisture content (g/gsolid) Me- equilibrium moisture content (g/g solid), t - frying time (s) a - half thickness of the product slice (m)

Moisture content

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Effect of oil temperature and vacuum pressure

(Garayo and Moreira, 2002)

Shrinkage

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Oil distribution pattern in vacuum fried potato slices at 130°C

(Carla, 2010)

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Vacuum frying Vs Traditional Frying

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Oil content within product

S.No Frying temperature

(°C) & method

Internal oil content

(g/g solid )

Surface oil Content

(g/g solid )

Total oil content

(g/g solid )

1. Vacuum frying at 120 0.072 0.339 0.410

2. Vacuum frying at 130 0.062 0.413 0.475

3. Vacuum frying at 140 0.059 0.398 0.457

4. Atmospheric frying at 185 0.50 - -

(Carla, 2010)

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Oil content various products

Comparison between oil content of product fried in vacuum and traditionalfryers (white-bar: traditional fryer; and black-bar: vacuum fryer)

(Paulo et al., 2008)

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Blue potato fried - vacuum fryer Blue potato fried - traditional fryer

Green bean fried - vacuum fryer Green bean fried - traditional fryer

(Dueik et al., 2010)

Color of product

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Sweet potato fried - vacuum fryer Sweet potato fried - traditional fryer

Mango fried - traditional fryerMango fried - vacuum fryer

(Dueik et al., 2010)

Color of product

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Oil properties affects Frying

Oil properties get affected during Frying

•Viscosity •Oxidation

•Oil aging •Hydrolysis

•Stability

•Free fatty acids

Oil property

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Oil quality

• TBHQ- SO - sunflower oil with synthetic antioxidant (tertiary- butylhydroquinone) • HOSO - sunflower oil with high oleic acid

Quality Factors

• Oil degradation

• Fatty acid composition - PUFA and MUFA

• ᾳ - Tocopherol

Peroxide Value in TBHQ-SOv treatment, are higher than TBHQ-SOt at least 2.32 times in period 2 and 1.86 times in the period 3 (Crosa et al., 2014)

PUFA - Poly unsaturated fatty acid; MUFA - mono unsaturated fatty acid

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S.No Quality parameters Traditional frying

Vacuum frying

TBHQ –SO

HOSO TBHQ –SO

HOSO

1. Free fatty acid (g oleic acid/100 g) 0.201 0.327 0.073 0.099

2. p- Anisidine (AnV) 207.0 82.0 25.8 33.3

3. Total polar compounds (%) 25.0 21.9 11.2 6.44. Reduction in ᾳ - Tocopherol (%) 53.62 99.76 4.90 96.87

*TBHQ- SO - sunflower oil with synthetic antioxidant (tertiary- butylhydroquinone)*HOSO - sunflower oil with high oleic acid content

(Crosa et al., 2014)

Comparison of quality parameters

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• Preserves natural Color

• Low moisture content - < 6%

• Reduced Shrinkage

• Low water activity - < 0.3

• Heat sensitive nutrients – preserves 90% of trans –carotene

• Prevention of carcinogenic compounds formation – 97% less acrylamide in potato

chips

• Reduce the fat content – 80 – 85% less oil in potato chips

• Suitable for high sugar content products

• Less adverts effects on oil qualityGranada et al, (2004), Clara. 2010.,

Merits of Vacuum frying

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• Skilled person

• Requires special packaging

• Pre – frying steps – Battering, instant extrusion

• Cost

• Time

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Limitations

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• The vacuum frying conditions (temperature and time) for various food products varied considerably and there was also a wide variation in the vacuum pressures used

• The choice of the vacuum frying conditions for the food samples was dictated by a range of physical parameters, as well as pre-treatment conditions

• There was no other way to design a vacuum frying process for a specific product except to carry out experiments to obtain an optimized process

Summary

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• Crosa, M. J, Verónica, S., Mónica, C., Laura, O., Roberto, S., Gabriela, S., and Marina, T. 2014. Changes produced in oils during vacuum and traditional frying of potato Chips. Food Chem. 146 (4) 603–607

• Dueik, V., Robert, P and Bouchon, P. 2010. Vacuum frying reduces oil uptake and improves the quality parameters of carrot crisps. Food Chem. 119 : 1143–1149

• Garayo, J., and Moreira, R. G. 2002. Vacuum frying of potato chips. J. Food Proc. Engng. 55(2): 181-191

• Granda, C., Moreira, R. G., and Tichy, S. E. 2004. Reduction of acrylamide formation in potato chips by low-temperature vacuum frying. J. of Food Sci. 69(8): 405- 411

References

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• Mariscal, M. and Bouchon, P. 2008. Comparison between atmospheric and vacuum frying of apple slices. Food Chem. 107: 1561–1569

• Moreira, R.G., Da Silva, P.F., and Gomes, C. 2009. The effect of a de-iling mechanism on the production of high quality vacuum fried potato chips. J. of Food Engng. 92: 297-304

• Muanmai, A., Kuluma, C., Punnarai, S., and Noppawan, T. 2007. Effect of antibrowning agents on banana slices and vacuum-fried slices. J. of Food Agri.and Envi. Vol.5:151 -157

• Ophithakorn, T., & Yamsaengsung, R. 2003. Oil absorption during vacuum frying of tofu. In PSU-UNS international conference. Energy and the environment, December 2003, Hat Yai, Songkhla, Thailand

• Paulo F. Da Silva and Rosana G. Moreira. 2008. Vacuum frying of high-quality fruit and vegetable-based snacks. Food Sci. and Technol.41 (8):1758 – 1767

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• Perez-Tinoco, M.R., Perez, A., Salgado-Cervantes, M., Reynes, M. and Vaillant, F. 2008. Effect of vacuum frying on main physicochemical and nutritional quality parameters of pineapple chips. J. of Sci. Food and Agri. 88: 945–953

• Rafael.H. V. V., Quiceno G. C. M., and Giraldo G. G. A. 2012. Effect of vacuum frying process on the quality of a snack of mango (Manguifera indica L.). ACTA AGRONÓMICA. 61 (1): 40-49

• Shyu, S.L Lung-Bin, H., and Hwang, L. S. 1998. effect of vacuum frying on the oxidative stability of oils .J. American Oil Cor. Soc. 75 (10): 132 – 138

• Song X, Zhang M, Mujumdar A. S. 2007. Optimization of vacuum microwave pre-drying and vacuum frying conditions to produce fried potato chips. Drying Technol, 25: 2027-2034

• Sonntag, R.E., Claus, B., and Gordon, J. V.W., 2003. Fundamentals of Thermodynamics. John Wiley & Sons, Inc. USA. 1894- 1921

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INNOVATIONS CONTINUES UNTIL THE THRUST FOR KNOWLEDGE

CONTINUES!!!!!!

NEED - ENDLESS

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