Extraction and characterization of essential oil of nutmeg (Myristica fragrans) fruit pericarp and utilization as a surface coating material to improve the shelf life of paneer

Paneer is a traditional dairy product of India and is similar to unripened soft cheese. It is used as a raw material for the preparation of a variety of culinary dishes and snacks. Paneer is marble white in appearance, with a firm, cohesive and spongy body and a sweetish-acidic-nutty flavor. But it is highly perishable with a limited shelf- life like other indigenous dairy products. Its shelf life was reported to be only six days under refrigeration, though its freshness is lost within three days. The spoilage of paneer occurs mainly due to the growth of microorganisms, which bring about various physico-chemical changes. In the present study, attempts were made to increase the shelf-life of paneer at refrigerated storage by the application ofnutmeg pericarp essential oil surface coating. The essential oil was prepared from fresh nutmeg fruit flesh by steam distillation method. The physico-chemical and bio functional properties of essential oil were determined. The specific gravity and refractive index of the essential oil were found to be 0.903 and 1.477 respectively. The acid value and total polyphenolic value of essential oil were 3.36 and 4.04 mg GAE/g respectively. The essential oil was also found to have good antimicrobial and antioxidant activity. The shelf life of samples coated with essential oil packaged in LDPE pouches had more shelf life than the control paneer, as the coated paneer kept well for 9 days while the control paneer spoiled after the 6th day of refrigerated storage. The paneer with essential oil coating obtained satisfactory sensory score

Effect of thermization of dahi on post fermentation acidification during refrigerated storage

Post fermentation acidification is defined as the development of acidity past the desired level of fermentation or acid development. Effect of thermization at 65oC for different periods (30 sec, 60 sec, 2 min and 5 min) on post fermentation acidification of dahi samples prepared using Lacticaseibacillus rhamnosus 18 or Lacticaseibacillus casei 01 upon refrigerated storage was assessed in this study. Significant changes (p< 0.01) were observed between the two starter cultures in terms of their post acidification potential with L. rhamnosus 18 dahi showing lower pH, higher titratable acidity and lactobacilli count than L. casei 01 during refrigerated storage. On assessing the impact of heat treatment on post acidification, significant decrease (p< 0.05) in pH, increase (p< 0.01) in titratable acidity and lactobacilli count of the heat treated and control samples were observed throughout the storage. Based on this study, it can be inferred that heat treatment at 65oC for even upto 5 min is not having any significant inhibitory effect on post fermentation acidification characteristics of the lactobacilli cultures tested

Isolation, Identification and Characterization of Thermoduric Psychrotrophic Bacteria from Market Samples of Pasteurized Milk Collected from Mannuthy, Kerala State, India

Aims: To isolate, identify and characterize thermoduric psychrotrophic bacteria from locally available market samples of pasteurized milk. Study Design: Market samples of pasteurized milk were collected, subjected to laboratory pasteurization and thermoduric psychrotrophic bacteria were enumerated after 10 days of storage at 7ºC.The isolates obtained were identified by 16S rRNA sequencing and subsequent blasting. The isolates were characterized in terms of haemolytic, lipolytic and proteolytic activities. Selected isolates were also assessed for their decimal reduction time at 63ºC.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Place and Duration of Study: Verghese Kurien Institute of Dairy and Food Technology,&nbsp;&nbsp; (Formerly College of Dairy Science and Technology), Mannuthy, Thrissur, Kerala between September, 2019 to March, 2021. Methodology: A total of 42 market samples of pasteurized milk belonging to seven different brands were assessed for their thermoduric psychrotrophic bacterial population. The thermoduric psychrotrophic bacterial isolates were identified by 16S rRNA sequencing and the sequences obtained were searched with the NCBI BLAST program (http://www.ncbi.nlm.nih.gov) for their closest relatives/reference strains with a homology of over or equal to 99 per cent. Haemolytic, proteolytic and lipolytic activities of the isolates&nbsp; were determined by&nbsp; streaking&nbsp; them on blood agar, skim milk agar (SMA) and tributyrin agar respectively and&nbsp; grading them based on the presence or absence&nbsp; of zone of clearance around the colonies developed. Decimal reduction time at 63ºC of two selected isolates was also determined. Results: Six thermoduric psychrotrophic bacteria were isolated from the 42 market samples of pasteurized milk i.e., only 14.3 % of tested samples had thermoduric psychrotrophic bacterial population. 16S rRNA sequencing and subsequent blasting identified the isolates as Aeromonas caviae, Moraxella osloensis, Delftia tsuruhatensis, Staphylococcus arlettae and two strains of Carnobacterium maltaromaticum. On assessing the haemolytic activity of the isolates, A.caviae DMV01 exhibited α haemolytic activity whereas Staphylococcus arlettae DMV02, M. osloensis DMV03, C. maltaromaticum DMV05 and C. maltaromaticum DMV06 exhibited ϒ haemolytic activities.&nbsp; A. caviae DMV01 was found to be lipolytic and the two Carnobacterium strains exhibited proteolytic activities. Staphylococcus arlettae DMV02 was found to be both proteolytic and lipolytic. Aeromonas caviae DMV01 exhibited&nbsp;D63 value of 4 minutes 38 seconds whereas for Moraxella osloensis DMV03 it was 25 minutes 18 seconds. Conclusion:&nbsp;&nbsp;Exhibition of heat resistance by microorganisms capable of low temperature growth presents quite a challenging situation in terms of quality assurance and shelf life extension of pasteurized milk. So it is high time that dairy industry takes up initiatives to remain updated with the changes happening in pasteurized milk microflora in order to address the challenges such microorganisms may pose in future