Combined Effects of Salting, Oregano Oil and Vacuum-Packaging
on the Shelf-Life of Refrigerated Trout Fillets
Presented by
Group 3
ID. 1803013-1803019
Md. Atique Ashab, Md. Shaif Rahman,Taposh Kumar, Shathi Dev
Nath, Ibne Sina

INTRODUCTION
Limited information in the
literature on the effect of
essential oils (EOs), used singly
or in combination with other
preservative technologies on
extension of shelf-life.
A fish belonging to the
Salmonidae family with high
commercial value and much
appreciated by European
consumers
Trout fillets in the form of
smoked and vacuum packaged
products are being exported to
various northern European
countries
Preservation using low-dose
irradiation, ice, ozonation,
packaging , combinations of
lactic acid-nisin has been being
practiced

Essential oils are
• regarded as ‘‘natural preservatives’’ to chemical preservatives
• their use in foods meets the current demands of consumers for mildly processed or natural
products
• aromatic oily liquids obtained from plant material : oregano, thyme, rosemary, clove, sage
and mint
• have been used to improve the sensory characteristics and extend the shelf-life of foods..
INTRODUCTION

The study was carried out-
To know the combined effects of salting, oregano oil and vacuum-
packaging on the shelf-life of refrigerated trout fillets
-by evaluating certain
microbiological,
Physicochemical
and sensory parameters.
OBJECTIVE

Sample
collection
Microbiological analyses
Physicochemical analyses
Sensory evaluation
MATERIALS AND METHOD
Figure : A brief outline of the study

• Total viable counts (TVC) were enumerated on Plate Count Agar and incubated
at 30 C for 3 days.
• Pseudomonads were enumerated on cetrimide fusidin cephaloridine agar and
incubated at 20 C for 2 days.
• Lactic acid bacteria (LAB) were enumerated on de Man Rogosa Sharpe agar
incubated at 25 C for 4–5 days.
• For Enterobacteriaceae and H2S-producing bacteria (including Shewanella
putrefaciens) enumeration, a 1.0 ml sample was inoculated into 10 ml of molten
(45 C) violet red bile glucose agar and Iron Agar , respectively.
Microbiological analyses

Physicochemical analysis
• Trimethylamine nitrogen (TMAN)
• Total volatile basic nitrogen (TVBN)
• Thiobarbituric acid (TBA)
TMAN and TVBN contents were expressed as mg TMAN/100 g, or TVB-N/100 g
fish muscle.
TBA content was expressed as mg of Malondialdehyde (MDA)/kg fish muscle.
Sensory evaluation : The attributes of cooked trout (odor and taste) were
evaluated by a panel of seven experienced judges on each day of sampling.
Physicochemical analysis & Sensory evaluation

Experimental Design
• Experiments were replicated twice.
• Analyses were run in triplicate
• Results are reported as mean values
standard deviation (S.D.)
• Data were subjected to analysis of
variance (ANOVA).
• The least significant difference (LSD)
procedure was used to test for
differences between means (P < 0.05)
A1 (Control, unsalted :air packaged)
A2 (salted: air packaged)
VP1 (salted, vacuum packaged)
VP2 (salted, vacuum packaged with
added oregano EO 0.2%)
VP3 (salted, vacuum packaged with
added oregano EO 0.4%)
The tested treatments were:

RESULTS AND DISCUSSION
Microbiological changes during storage
(a) Total Viable Counts (TVC) (b) Pseudomonas spp.
▪A1 : Unsalted; ♦A2: (salted: air packaged);
▲VP1: (salted, vacuum packaged);
●VP2 : (salted, vacuum packaged with added
oregano EO 0.2%);
□VP3 : (salted, vacuum packaged with added
oregano EO 0.4%)

(c) H2S-producing bacteria (d) LAB
▪A1 : Unsalted; ♦A2: (salted: air packaged);
▲VP1: (salted, vacuum packaged);
●VP2 : (salted, vacuum packaged with
added oregano EO 0.2%);
□VP3 : (salted, vacuum packaged with
added oregano EO 0.4%)
RESULTS AND DISCUSSION
Microbiological changes during storage

▪A1 : Unsalted; ♦A2: (salted: air packaged);
▲VP1: (salted, vacuum packaged);
●VP2 : (salted, vacuum packaged with added
oregano EO 0.2%);
□VP3 : (salted, vacuum packaged with added
oregano EO 0.4%)
(e) Enterobacteriaceae of chilled fresh trout
RESULTS AND DISCUSSION
Microbiological changes during storage
Lactic acid bacteria (LAB) , followed by H2S-producing bacteria , Pseudomonas spp. and
Enterobacteriaceae reached higher populations in A1, A2 (as compared to VP1, VP2 and VP3) trout
samples.

RESULTS AND DISCUSSION
Chemical changes during storage
▪A1 : Unsalted; ♦A2: (salted: air packaged);
▲VP1: (salted, vacuum packaged);●VP2 :
(salted, vacuum packaged with added
oregano EO 0.2%);□VP3 : (salted, vacuum
packaged with added oregano EO 0.4%)
(a) Total Volatile Basic Nitrogen (TVBN) and
(b) Trimethylamine Nitrogen (TMAN)
Treatments VP1, VP2 and VP3 produced significantly
lower (P < 0.05) total volatile basic nitrogen (TVBN) and
trimethylamine nitrogen (TMAN) values as compared to
the A1 and A2 samples

RESULTS AND DISCUSSION
Determination of shelf-life of trout samples based on sensory,
chemical, and microbiological analyses
Changes in odor (a), taste (b) and overall acceptability (c) scores of chilled fresh trout stored under aerobic conditions
▪A1 : Unsalted; ♦A2: (salted: air packaged); ▲VP1: (salted, vacuum packaged);
●VP2 : (salted, vacuum packaged with added oregano EO 0.2%);
□VP3 : (salted, vacuum packaged with added oregano EO 0.4%)

RESULTS AND DISCUSSION
Determination of shelf-life of trout samples based on sensory,
chemical, and microbiological analyses
Changes in odor (a), taste (b) and overall acceptability (c) scores of chilled fresh trout stored under aerobic
conditions
As determined by sensory
analysis the observed shelf-life
of trout fillets was
longest for VP2 (16–17 days)
VP1 (14 days),
A2 (8 days) and
A1 (5 days).
The presence of salt and oregano oil (0.2%) -
produced a distinct but sensorially acceptable
pleasant odor, well received by the panellists,
in contrast to the combined effect of salt and
oregano (0.4% v/wt)

• Addition of salt extended the product’s shelf-life by 9 days
• Whereas the combination of salt, oregano EO (0.2% v/wt) under VP
conditions resulted in a significant shelf-life extension of trout fillets,
i.e. by approximately 11–12 days, according to sensory data, as
compared to the control sample, kept under aerobic conditions.
CONCLUSION

FUTURE PROSPECT
• Further studies are needed with regard to preservation of fresh trout
using natural antimicrobials, including essential oils, in view of
consumers increasing demand for (preservative-free) fresh fish and sea
foods
• More specifically the need arises so as to establish optimum essential
oil concentrations that will maximize shelf-life, while at the same time
maintaining desirable freshness and quality (sensorial) characteristics.

Thank you