Apple quality

1. Maturity and ripening process in connection with Quality parametes
2. Quality parameters - measurement
*

maturity ripening
Stage of development of the fruits on the parental plant (only) Stage when biochemical changes convert inedible fruit into an edible product
*

*

that process occurs only when fruit is attached to the parental plant
a minimum period of development must be undergone by any fruit before harvest time
maturity ripening
stage when biochemical changes convert mature but inedible fruit into an edible product
can occur on or off the plant
ripening processes: softening, biosynthesis of volatile aroma, conversion of starch into sugar etc
At harvest time fruit must be mature but can be unripen (climacteric)
Fruit can be harvested when,
has acceptable eating quality at the time of harvest (non-climacteric)
or
has the potential to ripen into a product of accetable quality (climacteric)
*

Non-climacteric
Climacteric
fruits, vegetables with relatively
rapid increase in respiration rate
rapid ripening period = climacteric period
high ethylene production during ripening
can also be provoked to ripen by ethylene treatment
apple, apricot, avocado, banana,
kiwi, tomato
Fruits which mature slowly while attached to the parent plant
do not exhibit an increase in respiration rate when ripening begins,
low ethylene production rate, low respiration rate
their eating quality can not be improved after harvest
blueberry, cherry, grape, pineapple, potatoes
*

How to estimate optimal Harvest Time ?
CLIMACTERIC fruits (or vegetables )
pre-climacteric
ripen slower
respiration rate slower
not yet producing significant quantities of ethylene
maintain quality for longer
BUT
fruit picked up too early; does not develop its full potential
post-climacteric
ripening proces is speeded up
respiration rate increase faster
producing ethylene
quality cannot be kept for long
Climacteric period
*

How to estimate optimal Harvest Time ?
*

Determination of harvest date:
There are the principles which decided on which maturity and ripen stage fruit should be picked
It is crucial for storage, marketable life and quality
It is important to use objective criteria to decide when crop is ready to pick
Several maturity standards has been set for the major crops
Maturity standards can be:
starch,
firmness,
titratable acidity,
color changes,
soluble solids content
*

Starch index / Harvest index
starch SV
solid soluble concentration RE
firmness PE
STREIF index of ripeness: PE
RE x SV
*

Starch Index
Tool
potasium-iodide test
How?
10 apples should be taken from the ten different trees
cut apples equatorially into two halves
the cut sides of apple dip in the potassium-iodine solution
leave for 1-2 minutes
compare apples with the color chart
*

*

What is quality?
*

What is quality?
„fitness for use”
„is to meet the expectations of the consumer”
Quality means different for different people:
for the growers: quality is to achive high yield and big fruit size
for the transporters: quality is long storage potential
for the consumers: quality is nutritional value, eating quality (good taste and nice aroma, flavour)
Sometimes those requirements are in conflict.
*

What is quality?
Quality includes several characteristics of the products that consumers find or believe that are good indices of overall quality
QUALITY
NUTRITIONAL SENSORY
appearance
texture
aroma
taste
*

What is quality?
Quality includes several characteristics of the products that consumers find or believe that are good indics of overall quality
QUALITY
OBJECTIVE MEASUREMENTS
chemical parameters (sugar, water, starch etc)
SUBJECTIVE MEASUREMENTS
feel
taste
aroma
*

*

Quality parameters:
Size and shape
Skin color
Firmenss/texture
Starch / sugar (soluable solids content)
Titratable acidity
Volatile compounds / aroma / odour
Taste
Flavour (taste and odour)
*

Size and shape
Size is an individual unit of the product, but can significantly affect consumer appeal
Often the quality is discriminated based on size (consumer shopping), which is mistaken
Size can also affect handling precise or storage potential
Shape is indyvidual factor in distinguishing between idyvidual cultivars
Shape can eliminate product from potential market
*

*

*

Quality parameters:
Size and shape
Skin color
Firmness/texture
Starch / sugar (soluble solids content)
Titratable acidity
Volatile compounds / aroma / odour
Taste
Flavour (taste and odour)
*

Color
Chlorophyllases
Types of change in pigmentation:
Degradation of chlorophyll
Color changes during apple maturation and ripening are largly results of chlorophyll breakdown less chlorophyll
Unmasking of existing pigments
Synthesis of carotenoids
Synthesis of anthocyanins
*

Color
The loss of chlorophyll results in decreasing green color
Synthesis and/or unmaksking of anthocyanins result in red color
Synthesis and/or unmaksking of carotenoids result in yellow color
carotenoid
anthocyanin
*

Color
Anthocyanins are the most important in red apples
Anthocyanins are formed via 1. sugar path and 2. path of PAL enzyme activity
Many factors can affect coloring process:
Light is required for anthocyanin accumulation
Low temperature increases anthocyanin synthesis
High nitrogen availability and uptake delay the maturation process and also delay the synthesis of anthocyanin
Ethylene exposure stimulates PAL enzyme and anthocyanins accumulation
*
*

*

Color - analysis
Tool
Colorimeter Minolta
How?
Apple should be scanned by a colorimeter around its diameter a couple of times,
Results presented by units:
L = lightness
a = chromaticity coordinate between red and green
b = chromaticity coordinate between blue and yellow
*

L*= 43.31
a*= 47.63
b*= 14.12
*

*

Quality parameters:
Size and shape
Skin color
Firmenss/texture
Starch / sugar (soluble solids content)
Titratable acidity
Volatile compounds / aroma / odour
Taste
Flavour (taste and odour)
*

Firmness/texture
texture comprises those properties of a product that can be appraised visually or by touch
textural properties may also be assesed by muscle sense in the mouth so human perception of texture is determined by the way that fruits flesh breaks down during chewing
Texture is a quality factor, which include:
Firmness
Crispness
Juiciness
Mealiness
*

Firmness/texture
texture is a creation of composition of cells and their structure, therefore the turgor of cells is important in fleshy products
texture depends on maturity stage and storage conditons:
Advanced maturity: apples becoming soft, beans/peas become fibrous and hard
Chilling storage: potatoes hardcore – center of potatoes becoming woody and inedible
*

Firmness/texture
Firmness is a resistance to deformation by applied force
Firmness is the most used to descibe texture, sometimes it is only one quality parameter (New Zealand-kiwifruits)
Mealiness in sensory profiling is described by: softness, dryness, flouriness, granularity
Mealiness is mostly perceived as unpleasent by consumers (exception older people generation)
*
Texture is a quality factor, which include:
Firmness
Crispness
Juiciness
Mealiness

Firmness/texture - analysis
Tool
firmness can be measured by penetrometer, a simple pressure gauge also by Texture Analyser TA
How to do it?
approximately 10 apples should be analysed
a piece of peel is taken off at the widest diameter of each apple (both opposite sides)
the pin of the penetrometer should be gently thrust into this area
the device shows the resistance measured
the process is repeated on both apple sides
the value should be an average from two measurements.
*

Texture Analyser
*

Firmness-exercise
*

Quality parameters:
Size and shape
Skin color
Firmenss/texture
Starch / sugar (soluble solids content)
Titratable acidity
Volatile compounds / aroma / odour
Taste
Flavour (taste and odour)
*

Starch
Starch is composed of two glucose polymers amylose and amylopectin,
During ripening process starch breaks down and converts into sugar, into the complex sugar sucrose and the reducing sugars glucose and fructose
The less starch the riper the fruit,
There is a relationship between starch loss and ethylene production
Sugars released during starch breakdown are utilized for respiratory metabolism
Sugar is an important measurement of internal quality because the taste of the fruit is primarily dependent on the sugar and acidity content
many factors can influence the sugar content of ripening fruit:exposure to the sun and shade, irrigation, rootstock, fertilization, weather conditions etc
*

*

Sugar - analysis
Tool
To determine the amount of total sugar in the fruit the hand refractometer/refractometer can be used
How?
press the juice from apple
put a small drop of the juice into the glass part of refractometer
repeat action several times in order to achieve a workable average
Sugar content is usually expressed by %Brix degrees (the relative "sugar weight" of a sample compared to distilled water)
*

Sugar -analysis
*

Sugar - analysis
Refractometer without any sample
Properly calibrated refractometer
Sample of some real grapes - time to make wine
*

Quality parameters:
Size and shape
Skin color
Firmenss/texture
Starch / sugar (soluble solids content)
Titratable acidity
Volatile compounds / aroma / odour
Taste
Flavour (taste and odour)
*

Titratable acidity
is a measurement of quality which gives clues as to determining the harvest date (brix:acid ratio)
there are many organic acids, but generally two/one are mainly in the fruit:

Titratable acidity
organic acids are utilized as respiratory substrates and as carbon skeleton for synthesis of the new compounds during ripening (respiration, create aroma compounds...etc)
acidity decreases with increasing ripeness
the acidity can vary greatly from year to year, influenced mainly by weather conditions
*
*

Titratable acidity - analysis
Tool
To determine the acidity level in the fruit titration method is used
How?
press the juice from apple
measure 1ml of juice, add some water
start titration with NaOH (sodium hydrate)
acidity is expresed in malic acid g/l
*

Quality parameters:
Size and shape
Skin color
Firmenss/texture
Starch / sugar (soluble solids content)
Titratable acidity
Taste
Volatile compounds / aroma / odour
Flavour (taste and odour)
*

Taste
Consumers try to correlate visual parameters with taste (round, shinny, red apple has to taste good) – unfortunately we can assess taste only after purchase of the product
Taste is perceived by specialized taste buds on the tonque
There are many tastes but most appear to primarily represent combinations of 4 sensations :
Sweet
Sour
Bitter
Salt
*

Taste
Sweetness and sourness are predominant
Taste changes as the ratio of sugar and organic acids changes
Sweetness comes from amount and type of sugar in fruits (fructose>sucrose>glucose)
Sourness comes from amount and type of organic acids
*

Taste - exercise
*

Quality parameters:
Size and shape
Skin color
Firmenss/texture
Starch / sugar (soluble solids content)
Titratable acidity
Taste
Volatile compounds / aroma / odour
Flavour (taste and odour)
*

Apple Aroma
Over 300 volatile compounds have been measured in apples
The change in production of volatile compounds by apple fruit is closely linked to ripening process so also to ethylene
The types of apple aroma compounds produced typically belong to one of several groups, mostly esters, aldehydes, alcohols, ketons (others in smaller amounts)
*

Apple aroma
*

Apple aroma
In pre-climacteric apples, aldehydes and alcohols are the largest quantitative groups of volatile produced, but after ripening begins ester production increases and becomes the largest quantitative group in many cultivars
The most important is the treshold of each compound not a quantity of compound! !
treshold = ability to percive the odour
*

Aroma/Odor - analysis
GC-MS
*

Aroma/Odor - analysis
Olfactory GC
*

Aroma - exercise
*

Quality parameters:
Size and shape
Skin color
Firmenss/texture
Starch / sugar (soluble solids content)
Titratable acidity
Volatile compounds / aroma / odour
Taste
Flavour (taste and odour)
*

Flavour
TASTE + ODOUR
PERCEIVED BY BUDS IN THE TONGUE
PERCEIVED BY OLFACTORY RECEPTORS IN THE NOSE
*

Flavour
TASTE + ODOUR
PERCEIVED BY BUDS IN THE TONGUE
PERCEIVED BY OLFACTORY RECEPTORS IN THE NOSE
”...This wine tastes so nice, because of its fruity and spicy notes...”
The sentence refers to pleasant odor sensed, when taste can be describe only by 4 sensations: sweet, salty, sour and bitter.
*

*

Exercise 3
10.03.2009
Lab on the 4th floor (at my office T459)
Each group = different time
*

Exercise 3
*
Group 1 (opponent to group …) at 15.15
Aslan, Ozlem
Østergaard, Anne
Betzer, Cathrine
Group 2 (opponent to group …) at 11.00
Zidova, Petra
Dedenroth, Stine Elise
Yilmaz, Tuba
Group 3 (opponent to group …) at 15.00
Demir, Kevser Burcu
Weinreich, Christine Frigaard
Desta, Zeratsion Abera
Group 4 (opponent to group …) at 14.00
Thach, Tine
Dobrynin, Aleksey
Stalmach, Joanna
Group 5 (opponent to group …) at 14.30
Gardin, Jeanne
Shahid, Aleena
Gruca, Marta
Helene
Group 6 (opponent to group …) at 13.00
Sarica, Gülsen
Hansen, Majbrit
Rodriguez Algaba, Julian
Group 7 (opponent to group …) at 13.30
Jacobsen, Stine Kramer
Orhan, Damla
Kemezys, Andrius
Group 8 (opponent to group …) at 11.30
Mutlu, Ayse Ceren
Kjeldgaard, Karina Juhlert
Mlynek, Janus Cronquist
Mengistu, Fekadu Gebretensay

Exercise 3 - delivery
13.03.2009
Tåstrup 8-01
Oral presentation of the exercise results (10+10min)
Groups examine each other
*