DEVELOPMENT OF ON-PACKAGING FRESHNESS INDICATOR OF MISTI DAHI
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Date
2022
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Publisher
ICAR-NDRI, KARNAL
Abstract
A freshness indicator is a type of non-destructive intelligent packaging system which tells
about the real-time quality of the product. Intelligent packaging is a growing research area
but limited research has been done on dairy products in general and fermented dairy
products in specific. India is the largest producer of milk in the world with about 210 MT
of production of which about 50% is converted into traditional dairy products. Misti dahi
is a popular traditional fermented dairy product of eastern India, which is having a shelf
life of about 15-20 days. The shelf life of the product depends on the processing conditions
and also on its storage conditions. Hence, present research work has been carried out to
develop an on-package freshness indicator for misti dahi. The research was conducted in
three phases, in the first phase headspace volatiles of both homogenized and
unhomogenized misti dahi were identified using Gas Chromatography-Mass Spectrometry
(GC-MS) coupled with Solid Phase Microextraction (SPME) technique. A total of 192
and 191 headspace volatile compounds were identified in homogenized and
unhomogenized misti dahi respectively, having a Total Ion Count (TIC) of more than 104.
The chemical groups identified were acids, ketones, ether, esters, aldehyde, alcohol,
hydrocarbons, nitrogenous compounds, sulphur-containing compounds, and some
miscellaneous compounds. Among all groups, 8 key headspace volatiles were identified
which were present on all days of storage namely acetic acid, hexanoic acid, octanoic
acid, n-decanoic acid, 2-heptanone, 2-nonanone, 2-undecanone, and nonanal. In the
second stage, during storage, quality attributes of misti dahi were monitored and correlated
with key headspace volatile compounds. The key headspace volatiles were found to be
positively correlated with titratable acidity (% lactic acid), free fatty acid content (% oleic
acid), Thiobarbituric acid (TBA) value and yeast and mold counts. While negatively
correlated with pH and total viable count. Overall acceptability was found to be both
positively and negatively correlated with the different headspace volatile compounds. It
was observed that misti dahi lost its freshness on the 20th day of storage and mold growth
was visible on the 25th day. In the third and the last phase, the earlier developed freshness
indicators for dahi (Suwalka, 2019) namely S-16 10, U-40, and U-50 were used as
freshness indicators of misti dahi. However, as expected desired colorimetric changes
were not observed owing to the compositional differences in both the products. Later, 13
new formulations were developed and tried and at the end freshness indicators with codes
XE and XD+ were found to aptly depict the freshness loss and selected for homogenized
and unhomogenized misti dahi, respectively. The qualitative and quantitative colour
changes in both the freshness indicators were monitored during the storage and found to
change from an initial yellow colour to pale pink at the end of 20 days indicating loss of
freshness. Both the freshness indicators (XE & XD+) were found to be stable at 6±2 ℃
for a minimum of 60 days. Also, a model was developed for predicting the ΔE of the
freshness indicators based on critical spoilage indicators of misti dahi. It could be
concluded that the freshness indicator labels (XE and XD+) were developed successfully
for homogenized and unhomogenized misti dahi which depicts the real-time freshness of
the product during storage.