Lecture 10- Quality & Maturity Indices Harvesting Methods

what is quality of fruits and veggies

Quality of fruits and vegetables is a combination of various physico-chemical and nutritional characteristics that give them value or wholesomeness as a food item

does quality apply same to all fruits and veggies

Quality can only be defined for a specific commodity and for a specific use

• quality is fruits and veggies specific

what are the different components that go into quality?

1. appearance or visual/esthetic factors

2. texture or mouth/finger feel factors

3. flavour (Taste &Smell) 

4. Nutritive value 

5. safety or antinutritional factors 

explain appearance and quality 

relates to size, shape, color, gloss, defects 

explain texture or mouth/finger feel factors AND quality

firmness, hardness, softness, juicyness, toughness, fibrousness, grittyness

explain flavour and quality

Subjective and objective evaluations

explain nutritive value and quality

protein, carbohydrate, fat, vitamins, minerals, etc

what are different types of defects in quality

1. morphological defects

2. physical defects

3. mechanical damages

4. physiological defects

5. pathological defects

6. entomological defects

MMEPPP

explain morphological defects 

Sprouting of potatoes, onions & garlic

Elongation & curvature of aparagus

Seed germination in tomatoes & peppers

explain physical defects

Shriveling & wilting as a result of water loss

explain mechanical damages

Puncture, cuts, crushing & abrasion

explain physiological defects 

Chilling & freezing injury

Internal breakdown

explain pathological defects 

Fungal & bacterial decay (blue & grey mold etc.)

explain entomological defects

Damages caused by insects & pests etc.

who is concerned with quality in the produce chain

Grower, shipper, wholesaler, distributor, retailer, consumer

explain different perspective of qualitues of consumers, everyone, and plant breeders 

Appearance factors: everybody’s concern

Plant breeders/farmers: Priority is yield & resistance to disease

Consumer: good appearance, firm, good flavor & nutritive value

why are quality factors important

setting standards specifications

explain grading in US vs Canada

USDA: Quality standards

Fancy, Choice and Standard

Canada:

Grade A, B, C

what are factors that influence quality 

1. genetic factors 

2. environmental factors 

3. temperature 

4. light 

5. cultural factors 

explain how genetic factors influences quality

cultivars, rootstocks, selection of specific varieties, GMO

explain environmental factors influence quality

1. climate: Temperature, Light, Rainfall, Irrigation, Wind

2. cultural: Soil type, Mineral nutrition, Water supply, Pruning, Thinning, Application of Pesticides, Growth regulators

3. rainfall

4. soil texture

5. wind factors

explain temp and quality 

every commodity has a tolerance range for optimal growth 

• Within TR, higher the temperature, faster the growth

higher temperatures…

earlier the harvest

what is temperature summation

Indicator of harvest maturity (degree-day – Heat Unit)

what is the mean heat unit 

(Mean temperature – Reference temperature) (F) x Time (h or day)

expressed as degree hr OR degree-days

what is degree hour

accumulated heat unit equivalent to the exposure of the crop to one degree above the reference temperature for one hour

what is degree day

exposure at one degree above the reference temperature for one day (24 h)

what are ideal conditions for plant growth

warm days and cool nights

warm days: greater photosynthetic activity – better storage of food reserves

cool nights: lower respiration – lower depletion of stored reserve

what is ideal scenario for tropical fruit?

night temperature ~ day temperature

Produce fruit quality is generally different –higher accumulation during the day and higher depletion of stored reserve during nigh

give example of temp can affect citrus fruits 

Oranges from Texas & Florida receive more than double heat units than the ones from California

Quality differences: Florida & Texas oranges are sweeter

explain different components of how light influences quality

1. duration of light

2. intensity

3. quality

explain duration of light and quality

Longer day, shorter nights better than converse

More photosynthetic and less depletory activity

Results are reflected in the composition

explain intensity and quality

1. Higher the intensity, higher the sweetness and lower the acidity in the fruit

2. Higher intensity also results in fading of colors

3. Density of planting influences light intensity

canopy shading? 

Tomatoes with deeper red color and cucumbers with deeper green color

explain high intensity plant affects plants

High intensity planting means lower exposure to light and therefore lower photosynthetic activity – lower sweetness

explain quality of light and quality of commodity

important in pigmentation

rex: Purple cabbage or eggplant derive their color from exposure to blue & violet light

what color occurs from direct sunlight 

Direct exposure to sunlight will result in green color

explain cultural factors influence quality

1. mineral nutrition

2. cultural practices: pruning, fruit thinning, planting: high vs low density

3. chemical sprays/growth regulators

examples of cultural factors?

1. pesticides

• petroleum oil sprays for citrus pests

1. abscission preventing

• control fruit crop

examples of abscission Preventing?

2,4,5 T (2,4,5 trichloro phenoxy acetic acid)

NAA (Naphthalein acetic acid)

CPA (p-chloro phenoxy acetic acid)

Alar (applied 60-70 days prior to harvest apples)

explain cultural factors- postharvest treatments  & quality 

storage conditions, fungicides and irradiation 

when do you know when right stage to harvest?

can ask three questions:

1. Which parameters can be used?

2. How the parameter is related to the maturity?

3. How it can be used to predict maturity?

definition of optimum maturity?

That stage of maturity at which a commodity has reached sufficient stage of development that after harvesting & post-harvest handling (including ripening) the quality will be acceptable to consumers

phyisico-chemical indicators of ripening of tomatoes? 

what are some maturity/quality indices?

Elapsed days from full bloom

Meat heat units

Size

Specific gravity

Solidity

Texture properties - firmness, hardness etc Color Chemical tests

chemical tests

what are some chemical tests for maturity/quality indices

Starch,

Sugar

Ascorbic acid,

AIS

Acidity

Enzyme activity

Respiration rate

definition of harvest? 

the process of detaching a produce

when harvest should happen?

At proper maturity stage

By proper technique

As rapidly as possible

With minimum damage or loss

Types of harvest?

hand VS mechanical

Hand harvesting ADV. vs DIS 

ADV: 

Selective pickings

Minimum damage

Minimum capital investment

Output = f (number of people at work)

DIS: 

Shortage or labor

Labor srikes costly

Permanent labor force – not feasible

Need efficient labor management

frsh market fruits and veggies are mostly?

hand harvested

when do you mechanized harvesting>

Employed for crops intended for processing

Produce converted to other forms

Physical appearance not an major consideration

Commodity consumed within short time 

Commodity is normally needed in bulk lots

ADV for mechanical harvesting 

Speed of harvest

Improved conditions for the workers

Reduced labor related problems

what are some incentatives for mechanical harvesting?

Increase cost of manual labor

Decreasing availability of timely labor

Need for high speed-high volume output

DIS of mechanical harvesting

Physical/mechanical damage to the crop

Non selective

Separation of plant debris

Damage to fruit trees during harvesting

Large volume output

Machinery expensive

Social impact

what are the different elements of harvesting

1. detection 

2. selection 

3. detachment: Mechanical and hand 

4. collection 

5. separation 

6. handling 

what are some field considerations for mechanized harvesting

1. genetic considerations: tree, crop, strength

2. planting sustem and tree training: high desnity

3. crop control: pruning, fruit thinning, hand and chemiclas

4. harvest control: pre harvest sprays

why use growth regulators/ harvest sprays

1. increase size of teh fruiit: Alar (prebloom application) Ethephon (prebloom a

2. sprout inhbitor

MH (maleic hydrazide): very common (onions) MENA (methyl ester of NAA)

1. fruit thinning: NAA, CPA, Ethephon

what are growth regulator for altering the maturity date 

lar : both growth inhibitor & growth promotor Retards ripening of pome fruits Accelerates ripening of stone fruits Intensifies the red color of apples Ethephon Advances the maturity date Chemicals in postharvest applications Fungicides, fungistats Desinfectants, fumigants

what are the two types of mechanical harvesters

1. direct contact devices: cutting, pulling, snapping, twisting, stripping, digging, lifting etc

2. vibratory devices: Trunk & limb shakers with catch frame & canvas

what are harvest aids

Mechanical device/support which assists in improving the hand harvest operations

what are examples of harvest aids

Picker pole with a knife and a canvas bag

Single/multi station platforms (to position workers)

Conveyor belt (to move harvested heavy produce)

Harvesting cages

Lights for night time harvesting

what happens after mechanization

Fresh market : less than 25%

Processing : more than 75%