Sensory Evaluation of Milk Powder

The sensory evaluation of milk powders assumes great significance in our country. Milk powders, particularly skim milk powder (SMP) is manufactured in large quantities at feeder balancing plants in the flush season and subsequently used in lean period in reconstituted form to maintain milk supply. Also it has become an important export commodity. In this chapter we shall discuss the sensory evaluation of both, whole milk powder (WMP) and Skim Milk Powder SMP.

i. Desirable Attributes and Defects in Milk Powders

i) WMP: The flavour of dry whole milk should be clean, rich, sweet and pleasant.Frequently, dry milk may be unduly criticized as having a heated ‘or a ‘cooked’ taste. This may be expected or even desired. The common flavour defects of WMP are oxidized/tallowy, chalky, scorched, rancid and stale. The product should be free flowing to some extent with absence of lumps. Presence of hard lumps is a serious defect in WMP. The colour of WMP depending on the source of fat varies from white to deep yellow. The defects such as scorched particles, browning or lack of uniformity should be absent.

ii) SMP: The flavour of good quality SMP, when reconstituted should be similar to that of fresh skim milk, that is, normally a flat taste because of practically no fat in it. Otherwise, the flavour is clean, sweet and pleasant and may have a slightly cooked or heated perception. The chief flavour defects of SMP are stale/storage, neutralizer and scorched. SMP prepared by spray process is very fine in particle size and free flowing. The product pours readily somewhat like that of corn meal. Cake formation is the most frequently occurring defect related to texture of SMP. Sometime the defect is so serious that the product looks as hard as a rock. The colour of SMP should be uniform and showing complete absence of scorched particles and browning. The product should have a creamy white or light yellow colour.

iii. Score Card of Milk Powders

The weightage given to different attributes of milk powders is shown in table .

Score card for milk powders

iii. Scoring Technique of Milk Powders

i) Method of Reconstitution: Generally the dry milks are reconstituted to the composition of their native liquid form for examining odour, taste and presence of undissolved particles (sediments). The required quantities of WMP (13 g) and SMP (10g) are dissolved in warm water (40-45oC) to make the final volume to 100 ml and left for about 30 min before judging.

ii) Sequence of Observations

a) First of all observe the external condition of the package for cleanliness, neatness etc.

b) Open the package and immediately inhale the aroma. Take a small amount of powder in to mouth for taste and tactual perceptions.

c) Simultaneously observe the appearance of powder for colour, lack of lumps/ cakes and free flowing properties.

d) Then start judging the reconstituted milk adopting the same technique as discussed easier for fluid milk.

e) Try to correlate the flavour perceived in dry form with that noted in reconstituted form.

f) Record all observations along with intensity of defect, if any, in the score sheet.