Nondestructive Texture Assessment of Fruits and Vegetables by Itzhak Shmulevich Unlimited Postharvesting Leuven June 11-14, 2002

The Department of Agricultural Engineering Technion-Israel Institute of Technology

Technion-Israel Institute of Technology The Department of Civil & Environmental Engineering, Agricultural Engineering Option

Presentation outline Introduction - firmness quality nondestructive measurements; Impact technique vs. acoustic technique; Experimental report on various fruits; Results; Discussion; Conclusions.

QUALITY ASSESSMENT

Quality Factors of Agricultural Products Appearance - visual Texture - feel Flavor - taste and smell Safety Nutritive Value

Texture Texture can be defined by subjective terms such as: Firmness Mealiness, Hardness, Softness, Brittleness, Ripeness, Toughness, Chewiness, Smoothness, Crispness, Oiliness, Springiness, Toughness, Fibrousness, or Juiciness etc.

Quality Sensing in Commercial Settings Requirements Nondestructive External and internal properties Accuracy Speed (5-15 fruits/sec) Recognize inherent product variability

NONDESTRUCTIVE SENSOR TECHNOLOGY

Nondestructive Firmness Measurement Techniques Fruit Response to Force Detection by Impact Force Forced Vibrations Mechanical or Sonic Impulse Ultrasonic Techniques Indirect Firmness Measurement

Research Objective The motivation of the present work is to develop a fast nondestructive method for quality firmness testing of fruit and vegetable. q The general objective of the research is to compare sensing the fruit firmness using low mass impulse excitation to the acoustic response For quality assessment of fruit and vegetable.

Texture

Relationship between turgor pressure and tissue rigidity E=3.6 p +2.5 x107 [ dynes/cm2] Modulus of Elasticity

Nondestructive Firmness Measurement Impact Force Technique

Nondestructive Firmness Measurement Acoustic Technique

Method and Materials Mango (210) Kent cultiver; Shelf life conditions: 20 0C 50%RH; 12 days, ( 10 experiments): 80 fruit were tested daily only nondestructively 130 fruit were tested both nondestructively and destructively 12 fruit were tested daily; Special experimental set up for input and output signals measurements; Brix by digital refractometer, Atago's Palette 100. .

Low-Mass Impact (LMI) Firmness

IQ Firmness Sinclair International LTD IQ TM Firmness Tester

Destructive Firmness Measurement

Destructive Tests

Destructive Tests

Quality Detection by Impact Force Time [msec] Force [N]

Delwiche (1989 ,1991), Nahir et al. (1986 ) Quality Detection by Impact Force Chen. P (1996), Farabee (1991) Delwiche (1989 ,1991), Nahir et al. (1986 ) d sec N Fp Tp td

The Acoustic Parameters of a Fruit Natural frequencies and firmness index - FI FI = f 2 m 2/3 {104 kg2/3 s-2} where: f - first spherical resonant frequency m - fruit’s mass. Damping ratio - z The centeroid of the frequency response - fc

Firmalon Prototype

Firmalon

Typical Acoustic Fruit Response Time Domain Frequency Domain

Microphone Based System for Acoustic Firmness Testing Source: J. De Baerdemaeker

Comparison Between Two Acoustic Test Methods Method-A: Microphone Method-B: Piezoelectric-Film Sensor Source: N. Galili & J. De Baerdemaeker

Acoustic Firmness Sensor A F S TM Source: AWETA

Method and Materials Mango (319) Tommy Atkins cultivar; Shelf life conditions: 20 0C 50%RH; 13 days, ( 12 experiments): 25 fruits were tested daily both nondestructively and destructively; Three experiment set-up for input and output signals measurements; Brix by digital refractometer, Atago's Palette 100. .

Quality Detection by Impact Force

Correlation Between Firmness Index (FI) and Sinclair (IQ)

Results

Results

Summary The firmness indices from the two methods gave clear indications of the ripening process of mango fruit during shelf life. The Sinclair firmness tester (IQ) correlated well to the acoustic and the destructive tests than the low-mass impact (LMI) by pendulum technique. The good correlation between the firmness index, measured by an acoustic technique (FI) and the IQ firmness by Sinclair indicates that either of the two may successfully be implemented as an on-line sorter for mango fruit.

Current Research Sinclair International LTD IQ TM Firmness Tester

NONDESTRUCTIVE SENSOR TECHNOLOGY

Nondestructive Firmness Measurement Techniques Fruit Response to Force Detection by Impact Force Forced Vibrations Mechanical or Sonic Impulse Ultrasonic Techniques Indirect Firmness Measurement

Nondestructive Firmness Measurement Impact Force Technique

Nondestructive Firmness Measurement Acoustic Technique

Relationship between turgor pressure and tissue rigidity E=3.6 p +2.5 x107 [ dynes/cm2]

The Acoustic Parameters of a Fruit Natural frequencies and firmness index - FI FI = f 2 m 2/3 {104 kg2/3 s-2} where: f - first spherical resonant frequency m - fruit’s mass. Damping ratio - z The centeroid of the frequency response - fc

Destructive Firmness Measurement

Results

Parameters extracted from the measurements Low-Mass Impulse parameters: C1 = Fp/Tp; C2 = Fp/Tp2 ; w (-20); and fc(in). Acoustic parameters: f1 ; FI ; and fc(out); Destructive parameters: E ; Pene and Brix.

Quality Detection by Impact

Summary The new parameter of the input excitation signal in frequency domain fc(in) can give a clear indication of firmness and ripening degree of mango fruit, independently of fruit size and shape. Better correlations were achieved between the destructive indices and the input nondestructive parameter, as in compared to the output parameters. This can be explained by the fact that the output acoustic signal gives global indication of fruit properties and is sensitive to fruit shape, while the input signal represents local properties.

Summary (Cont. ) The good correlation between the input and output parameters of the nondestructive tests indicates that integration of the two may improve the accuracy of the nondestructive dynamic tests for mango quality assessment.

Method and Materials

Method and Materials Shelf life conditions: 20 0C 50%RH; Between 10 and 25 fruits were tested daily both nondestructively and destructively; Three experiment set-up for input and output signals measurements; Destructive test; Brix by digital refractometer, Atago's Palette 100. .

Results

Results

Correlation Between Firmness Index (FI) and Sinclair (IQ)

Pearson linear correlation between the nondestructive and destructive tests, n=280 Flamekiss-Nectarine, Correlation is significant at the 0.05 level

Pearson linear correlation between the nondestructive and destructive tests, n=150 Fuerte-Avocado, Correlation is significant at the 0.05 level

Pearson linear correlation between the nondestructive and destructive tests, n=160 Galia-Melon, Correlation is significant at the 0.05 level

Pearson linear correlation between the nondestructive and destructive tests, n=309 Tommy Atkins-Mango, Correlation is significant at the 0.05 level

Tommy Atkins-Mango n=309

Thanks For Your Attention Thanks to the organizer for a great Symposium

Pearson linear correlation between the nondestructive and destructive tests, n=205 Tomato, Correlation is significant at the 0.05 level