Nutrients often diminish as soon as they are picked from farm till they reach consumer and decline till they are eaten. In this presentation we will look into various unit operations and how they affect level of nutrition in Finished Goods. Let's have a look on some Do's and Dont's for technical professional as well consumer.

1. PRESERVING NUTRIENTS in FOOD
• NAME: Mansi Langalia
• COURSE: M.Sc. Food Technology

2. • Food provides the ideal mix of vitamins, minerals, and other nutrients. But the
nutrients in foods begin to decrease as soon as the food article is picked and
continues to decline until it is eaten. The sooner you eat the food, the less
chance of nutrient loss. The water-soluble vitamins, especially thiamine, folic
acid and vitamin C, can be destroyed during improper storage and excessive
cooking. Heat, light, exposure to air, cooking in water and alkalinity are all
factors that can destroy vitamins.
• If food is not eaten within several days, freezing is the best method to retain
nutrients. Frozen fruits and vegetables can be better than your grocer’s fresh
ones if they have been processed immediately after harvesting. Blanching
naturally stops enzymatic changes that destroys vitamins.
• Usually there are Three R’s to be followed while preserving nutrients in food:--
3 R’s
Reduce the amount of
water used in cooking
Reduce the cooking time
Reduce the surface area
of the food that is exposed

3. Effect of various Unit operations on
Nutritional Value
Size Reduction:
• The increase in surface area of food as a result of size reduction may cause
oxidation of fatty acids, carotenes by oxidative enzymes such as
peroxidases / lipoxygenase.
• Sliced and chopped vegetables leads to 78% decrease in their Vitamin C &
Thiamine levels. E.g.: Cucumber
• In dry milled foods loss of nutritional value result from separation of
components after size reduction. E.g.: During cereal & legume milling, the
aim is to remove fibrous seed coat from endosperm, meanwhile aleurone
and germ may be removed resulting in loss of nutrients like in case of
polished rice, pearled barley & white wheat fours.
• Cereals being important source of dietary fibre and this is substantially
decreased in Maida (1.5g in 100g) compared to whole wheat flour (5.8g in
100g).
• But often during some processes iron bio-availability increases due to
removal of bran along with complex polysaccharides, phytates , and other
phenolic compounds (Tannins).
• Size reduction also increase bio availability of various nutrients as when
particle size is reduced, there is more surface area for digestive enzymes to
act on.

4. Fermentation:
• Phytic acid hydrolysis during fermentation possess iron ion-chelating ability, and
thus they can probably prevent iron ion-induced lipid peroxidation in biological
systems and improve bioavailability of nutrients in body.
• Many industries add phytic acid to inhibit lipid peroxidation and concomitant
oxidative spoilage, such as discoloration, putrefaction, and syneresis.
• Fermentation of curd leads to enhancement of nutrients like vitamin B12,
Niacin & riboflavin.
• Fermentation has played major role in reduction of trypsin inhibitors,
phytates and flatus producing oligosaccharides.
Blanching:
• Traditional immersion techniques involving in-out water and solutes lead to
leaching from tissues of water soluble material (Vitamins & Minerals), sugars
& proteins.
• There is highest loss of vitamin C due to thermal liability and enzymatic
breakdown during storage thereafter.
• Steam blanching gives rise to lower losses of nutrients compared to
immersion techniques (In-container processing) as the main AIM is to
minimise leaching, thermal degradation and oxidase activity.
• Do not add baking soda in order to enhance colour as it destroys Thiamine &
Vitamin C.
• Avoid over-processing as like heating for more time.
• Immerse in cold water immediately for cooling as it is better for weight gain
and arrest nutrient destructive enzymes.

5. Canning:
• Presence of oxygen in container can lead to degradation of vitamin B & vitamin
C levels, thus ensure there is no leakage.
• Mineral content (Calcium content) of water used while processing also plays
major role in nutrient loss/preservation it is because water acts as a solvent for
heavy metal catalyst, that promotes oxidation of unsaturated nutrients.
• Maturity of food also plays major role in same, as article to be preserved should
not be over ripened or under ripened as it may affect stability of nutrients. E.g.
Naturally ripened fruits on plant has better nutrient concentrations.
• Concerned article for preservation should be usually stored as whole with less
slicing and no peeling to minimise chances of nutrient leaching.
• Many times ascorbic acid is added while preservation as a protective effect for
preserving Vitamin A & Vitamin E.
• Sulphites are also added as processing aid to preserve stability of vitamin C &
vitamin A.
• Canning leads to isomerization in Tomato from Trans Lycopene to Cis Lycopene
as it’s bioavailability is high (It is carotenoid which has antioxidant properties (a
substance that protects against cell damage).
Pasteurization:
• Pasteurized fruit juices should undergo deaeration (removal of dissolved gases,
such as oxygen, from liquids) for reducing losses of Vitamin C & Carotene.
• Ultra high temperature pasteurization especially of milk should be avoided as it can
destroy proteins and minerals like Iodine.
Smoking:
• Chemicals produced while smoking has antioxidant properties to preserve
nutrients like fat, proteins & vitamins. (Butyl gallate etc.)
• Smoking causes loss of moisture thus stability of nutrients is accompanied while
preservation.
.

6. Heat / Pressure Processing:
• Some industries add calcium oxide & sodium carbonate in order to retain
colour but studies shows that Alkaline pH results in loss of water soluble
vitamins.
• Ultra high temperature techniques involves rapid thermal degradation,
reduces antioxidants by 20-30%, oxidation & leaching, Beta carotene is
largely retained through the process.
• Technologists and analysts perform a test for amount of vitamin C lost and
threshold is set to allow maximum loss by 10-30%.
• Pressure cooking at small scale as well as large scale is beneficial for
retaining vitamins like A, B, E, K & C even at 900mPa.
• Always opt for high temperature and short time processing for better
preservation of nutrients.
Frying:
• Choose Baking over frying to prevent nutrients to be “washed out” of food because
of the use of fluids.
• Heating oil at high temperatures and deep frying it with starchy foods can lead to
oxidation of oils, decrease in iodine value and production of carcinogens.
• Inside out (baking/microwave) cooking over outside in cooking (frying) due to minimal
nutrient destruction.
• Reduce usage of thermally damaged oil (i.e. FFA more than 10% and fixed a limit for
Total Polar Compounds at 25% beyond ) as LYSINE (an essential amino acid)
content reduces.
• Opt for vacuum frying as concentration/point of action increase it will require less
time to cook the food article using low temperatures compared to traditional
commercial fryers.

7. Extrusion:
• Opting for low temperature while processing helps in better digestibility of
proteins.
• Opting for larger particle size of grains/cereal helps in lowering glycaemic
index by increasing digestion of resistant starch.
• Ensure that there is less or no metal ions involved from wear & tear of
extrusion parts.
• While processing TVP (Textured vegetable proteins) like soya chunks anti-
nutritional properties are destroyed which inhibits the digestion of proteins.
TVP is rich in protein & dietary fibre.
• Extrusion has possibility of controlling retro gradation of corn starch pastes
with selected additives such as galactomannans and citric acid , porcine
plasma protein hydrolyzates, various disaccharides and branched Polymers
and limit dextrin. Addition of antioxidant along with citric acid enhances
effectiveness of the process.
• Usually surface area is increased in expanded products thus again help in
preservation of nutrients.
• Prefer cold extrusion methods [compressive forming process (push-
through)]where oxidation is minimal, HTST (high retention of vitamin B than
longer time) or short barrel extrusion as there is less exposure to high
temperature over heat extrusion for better nutritional content in end product.
Dehydration:
• In dehydration as water is dried out and moisture content is
subsequently reduced, which leads to concentrated nutrient values %.
• Dehydration is best method of preservation of nutrients as well as
product shelf life itself. This method should follow short drying time, low
moisture, low temperature and reduced level of oxygen during packing
and storage.
• Fat oxidation is avoided as there is less interaction of fat soluble vitamin
with peroxides.

8. Chilling & Freezing:
• Cooking before chilling helps in maintaining stable beta carotene
value.
• Storage time should be reduced before processing, follow first in first
out techniques (FIFO).
• When freezing fruits & vegetables, avoid selecting bruised, injured and
excessive trimmed components as it accelerates nutrient losses.
• Cool/ Chiller (temperature not below 12C) the carcass soon after
butchering as acidic pH due to rigor mortis can cause denaturation of
proteins and increase drip losses.
• Studies show that Pre-supplementation with vitamin E before
butchering can help to minimise lipid oxidation due to antioxidant
properties of supplement.
Packing & Storage:
• Store finished good where oxygen levels are reduced and carbon
dioxide concentration to be 10%, this conditions will help in
preserving nutrients by minimising chances of oxidation.
• Avoid light exposure for storing kiwi as leads to reduction of vitamin C
levels, but on other hand increased light exposure for mango &
watermelon as it has no effect on it’s phenolic content.
• Opt for vacuum packing & MAP technology to reduce lipid oxidation.
• Milk should be stored in opaque container to prevent destruction of
riboflavin, vitamin A & D.
• Nitrogen flushing can also reduce oxidation & destruction of nutrients
during storage.

9. STABILITY OF NUTRIENTS
• This involves knowledge of stability of
nutrients under various different
conditions throughout its history from
farmer to consumer. Understanding the
product, processing, processing,
packaging & storage.
• Sensitivity of nutrients under various
conditions such as light/heat, oxygen, pH
range, water solubility & cooking losses
also affect essential nutrients and can
cause up to 75% loss, however modern
processing techniques may limit it up to
25%.
• Time and temperature of the processes
must be balanced between good
microbial destruction & minimal nutrient
destruction. Usually the final preparation
which involves steam/re-heating food at
home/restaurants can usually destroy
much which is previously stored
throughout prior processes.
• Let’s have look on table at right which
provides us with information about
various nutrients which are Stable (S)
and Unstable (U) in given conditions.

10. Some tips to preserve the Nutrients :-
• Refrigerate food in airtight moisture-proof containers as the loss of nutrients is slowed
near freezing temperatures, at high humidity, and less air contact. E.g.: Orange juice
can be kept refrigerated in a covered container for several days before any vitamin C
is lost.
• Avoid trimming and cutting fruits and vegetables into small pieces. The greater
surface area allows oxygen to break down vitamins faster. The outer leaves of all
greens and under the skins of fruits and vegetables, such as potatoes, carrots and
apples, have more nutrients than the inner portion.
• Microwaving cooking, steaming, or using a pan or wok with very small amounts of
water and a tight-fitting lid are best. More nutrients are retained when there is less
contact with water and a shorter cooking time with less exposure to heat. Cook fruits
and vegetables with their skins on.
• Minimize reheating food as cooked vegetables that are reheated after being kept in
the refrigerator for two or three days lose more than half their vitamin C.
• Do not add baking soda to enhance a vegetable’s green colour. Alkaline products
destroy Thiamine and vitamin C.
• Some methods which should be used for better preservation of nutrients are
steaming, grilling (coat them with olive oil. This promotes break down of the plant-cell
walls, releasing more antioxidants while the olive oil also helps your body absorb
carotenoids), baking & sautéing.
• Avoid re-heating as nutrient content is reduced by >30%.

11. • Keep fruits and vegetables refrigerated to prevent enzymes from destroying
vitamins.
• Store canned goods in a cool place and serve any liquid packed with the food. If you
don’t need all the liquid to cook the food, reserve the remaining for soup stock/Broth.
• Cooking in iron pots can destroy some vitamin C, but it can also add nutritious iron to
the food, especially if the food is acidic.
• Cooking utensils made of glass, stainless steel, aluminium, enamel or lined with a
non stick coating have no effect on nutrient content. The longer meat is roasted, the
more Vitamin B1 is lost.
• Except for pineapples, fruits ripened on the plant and in the sun have more vitamin C
than those picked green.
• Keep milk refrigerated and tightly capped, away from strong light. Riboflavin is very
sensitive to direct light.
• If food is cooked in water, add it to a small amount of boiling water, cover the pot and
cook it rapidly.
• When vegetables are cut into smaller pieces thus surface area decreases means
lesser cooking time.
• For high retention of vitamin C while cooking it is recommended that the vegetables
are cooked in low heat and small amounts of water for short periods to minimize the
loss of vitamin C.
• Alkaline pH should be avoided in the product as it contributes to loss of nutrients.