Physicochemical quality of duck meat marinated using Keranji (Dialium indium) and mini vacuum tumbler

A sustainable green economy in meat production must consider food safety principles, prevent the risk of meat contamination and improve meat quality. Duck meat has a darker colour than chicken meat, a distinctive aroma, tough texture and high fat, making it less preferred by consumers. This study aimed to determine the effect of Keranji marination using a mini vacuum tumbler on duck meat. This study used a complete factorial randomised design with four replicates. Factor I was the concentration of Keranji (D0=0%, D1=10%, D2=20% and D3=30%). Factor II is marination time using a mini vacuum tumbler (V1=15 minutes and V2=30 minutes). The results showed that Keranji concentration and marination time using a mini vacuum tumbler very significantly affected (P<0.01) pH, tenderness, cooking loss, moisture content and colour. The interaction between Keranji concentration and marination time using a mini vacuum tumbler significantly affects (<0.05) pH, cooking weight loss and tenderness. It was concluded that the best result was the best for Keranji with 20% concentration and marination time using a mini vacuum tumbler of 30 minutes. Keranji is recommended as a marinade that can sustainably improve the physicochemical quality of meat.


Introduction
Indonesia's green economy encourages continuous technological innovation to improve meat quality.Technology development with natural ingredients has been developed to produce quality meat products following consumer demand.The shift towards a sustainable green economy in meat production refers to food safety, reducing the risk of meat contamination, and improving the quality of meat products.Duck meat is a source of animal protein with a lower consumption pattern than chicken meat.The potential for duck livestock development is promising with the availability of natural resources in the form of feed.In addition, the tropical environment's carrying capacity also supports the development of the duck population.One of the problems regarding duck meat is that it has a darker colour than chicken meat, a distinctive aroma, toughness, and high fat, making it less preferred by consumers.Factors that influence the consumption pattern of duck meat are the quality and the low level of consumer preference.The quality of duck meat according to quality standards to meet consumer preference is expected.One option is several methods of improving the quality of duck meat using natural ingredients that are easy to apply.Modern equipment combined with natural ingredients is also needed to improve the quality of duck meat.
Laying ducks are livestock that thrive in tropical environments.Culled laying ducks are no longer productive, with an average age between 2 and 2.5 years.Cull ducks can be used as a source of meat because they can weigh up to 2 kilograms and are usually sold in pieces.Cull ducks produce meat that is tough, dark in colour, and has a distinctive smell.Duck meat has a distinct physical appearance and potential as a source of animal protein.Duck meat requires a long cooking time and temperature to be tender.However, the cooking length can affect the meat's quality because the microstructure and nutrient content can change [1].A method of easy processing duck meat that can maintain meat quality is needed.
Keranji (Dialium indium) is a fruit that usually grows in Java, Sumatra, and Kalimantan and spreads to various islands.Keranji is a sour fruit that grows in tropical environments and climates.Keranji is a black-shelled, orange flesh fruit with a tart, sweet, and fresh flavour.Based on various studies, it was found that starchy tamarind contains fibre, sugar, and fat and is high in vitamin C [2].Keranji tamarind or black velvet tamarind contains tannins, alkaloids, saponins, flavonoids, steroids, and cardiac glycosides [3][4].Starch tamarind fruit is a rich source of carbohydrates, fat, fibre, sodium, potassium, and vitamin C and is excellent for consumption.Marination processing using a vacuum marinator tumbler is soaking or smearing meat with a mixture of constituent spices, commonly called marinade [5].A vacuum marinator tumbler is a device used to carry out the marination process using vacuum technology.A tumbler refers to a design similar to a canister that can be used to put meat and marinade.In this case, the vacuum removes air inside the canister before marinating, creating a negative pressure.Combining Keranji marinade and vacuum marinator tumbler will improve marination efficiency and duck meat quality.Marination time should also be considered, as it can affect the quality of the meat.The physicochemical quality of meat needs attention during processing.Several factors will affect meat quality, such as livestock type, sex, age, rearing system, and feed.Factors that can affect meat quality after slaughter are the method of curing, storage, and tenderising agents.The physical properties of meat can be seen from the pH measurement, cooking weight loss, colour, and tenderness.Chemical quality can be known by measuring the nutritional content of meat, such as water content.This study aims to determine the effect of the addition of Keranji Acid processed using a vacuum marinator tumbler on the physicochemical quality of duck meat.This research is expected to have an impact on improving the physical quality of duck meat.

Research material
The materials needed are duck meat, keranji acid, and 70% alcohol aqua dest.The equipment required is a mini vacuum tumbler, filter paper, beaker (Pyrex), blender, grinder, sieve, stirring rod, water bath, thermometer, digital scale, Moisture meter, pH meter, Penetrometer, Colorimeter, and moisture meter.

Study design
This study used a complete randomised design factorial pattern with four replicates.Factor 1 is the concentration of keranji which consists of : D0 = No marination (control) D1 = Marination of duck meat using keranji fruit juice at a concentration of 10% D2 = Duck meat marination using keranji fruit juice at a concentration of 20% D3 = Marination of duck meat using keranji fruit juice at a concentration of 30% Factor II is marination time using a vacuum marinator tumbler consisting of: V1 = Marination time using a mini vacuum tumbler for 15 minutes V2 = Marination time using a mini vacuum tumbler for 30 minutes The samples in the study, namely factor 1 and factor 2, were each conducted with four replications, resulting in a total of 32 treatment combinations or 4x2x4 experimental units.

Procedures for making keranji marinade
Making marinade using the procedure starts with breaking the skin of fresh tamarind fruit and taking the contents, then mashing with a blender.Filtering is done to separate the extract and pulp.The vacuum procedure was carried out using an oxone marinate electric for 15 minutes, and the marination procedure was continued for 15 and 30 minutes.Calculation of concentration using the formula volume/volume or v/v to get 100 ml of solution using the formula / =  (%)   100 (1) 0% concentration (D0) = control Concentration 10% (D1) = 10/100 x 100 = 10 ml (10 ml of keranji juice + 90 ml aqua dest) Concentration 20% (D2) = 20/100 x 100 = 20 ml (20 ml of keranji juice + 80 ml aqua dest) Concentration 30% (D3) = 30/100 x 100 = 30 ml (30 ml of keranji juice + 70 ml aqua dest)

Parameter Testing
The pH value was tested using the AMT16M digital pH meter, moisture content using the DM300R Digital Moisture Meter, tenderness test using a penetrometer, colour testing using a colourimeter, and Cooking weight loss was carried out using the CSIRO method [1] then calculated by the formula:

Results and discussion
The marination process is an immersion method to improve quality using a mixture of spices or other liquids [6].The results of the study can be presented in Table 1.

pH
The results showed that the highest pH average was in D0 or control, and the lowest pH was in D3 or marinated duck meat using keranji in a mini vacuum tumbler for 30 minutes.The data showed that the pH of the control D0 was significantly different (P<0.05) from the pH of duck meat marinated with 10% keranji (D1).The pH of the control sample (D0) was very significantly different (P<0.01)from the pH of duck meat samples marinated using 20% (D2) and 30% (D3) keranji.Marination time using a mini vacuum tumbler in sample V1 (15 minutes) was significantly different from V2 (30 minutes).Marination using keranji had a very significant effect (P<0.01) on the pH of duck meat.Marination time using a mini vacuum tumbler in sample V1 (15 minutes) significantly differed from V2 (30 minutes).Marination using keranji had a very significant effect (P<0.01) on the pH of the meat of cull ducks.The results of the DMRT analysis showed an interaction between keranji marinade concentration and marination time using a mini vacuum tumbler on the pH of duck meat.The higher the concentration of keranji and the longer the marination time using a mini vacuum tumbler, the more the pH value of duck meat will increase.This means that the addition of keranji marinade with a high concentration and longer marination time will increase the pH of duck meat.Vacuum marinators are used to infuse the marinade into the meat, thereby increasing efficiency in the marinating process.A vacuum marinator works by removing air from the storage tumbler containing the meat and marinade.When the air is removed, the vacuum pressure helps the marinade to penetrate faster and deeper into the duck meat.This means that the longer the vacuum marination time, the more acidic the meat will be.Keranji fruit is acidic, so it lowers the pH of duck meat.Following the opinion of [7], keranji contains organic acids, namely malic, ascorbic, tartaric and citric acids and sugar.In the marination process, acidic fruits will help soften tough meat but can reduce pH.Acid-based spice marination needs to be considered because if the concentration is too high, it can cause damage to the texture of the meat.The right concentration is needed so that the texture of the meat is not damaged and the pH of the meat is not too low.Marinade ingredients that are organic acids can also inhibit microbial growth.Traditional Marination by soaking with fruits containing organic acids can be done for 30 minutes to maintain meat quality [8].Acid-based meat marination has two benefits: even though it can reduce the pH of the meat, it can tenderise the meat and reduce bacterial growth.Bacterial death due to organic acid-based Marination is caused by the accumulation of hydrogen ions (H+), which are toxic to bacteria.Hydrogen ions must be released by bacterial cells that require adenosine triphosphate (ATP).The higher the hydrogen ions accumulated by bacterial cells, the more ATP is needed.This causes bacteria to lack ATP so that bacterial growth is inhibited.The ultimate pH in normal meat is between 5.4-5.8[1].The pH value of duck meat with keranji marinade at different marination times using a mini vacuum tumbler for 15 minutes shows a limit that is still normal.The use of keranji for Marination at 10% (D1) and 20% (D2) at 15 minutes (V1) is the best result in this study.

Cooking weight loss
The results showed that the average cooking weight loss was highest in D0 or control and lowest in D3 or duck meat marinated using 30% keranji at a marination time of 15 minutes (V1).The data presented that cooking weight loss in control D0 was significantly different (P<0.05) with duck meat marinated with 10% keranji (D1).Cooking weight loss in the Control sample (D0) was very significantly different (P<0.01) with duck meat samples marinated using 20% (D2) and 30% (D3) keranji.Marination time using a mini vacuum tumbler in sample V1 (15 minutes) significantly differed from V2 (30 minutes).Marination using keranji had a very significant effect (P<0.01) on cooking weight loss of cull duck meat.The results of the DMRT analysis showed an interaction between keranji marinade concentration and marination time using a mini vacuum tumbler on cooking weight loss.The higher the concentration of keranji and Marination, the more time using a mini vacuum tumbler will reduce the cooking weight loss of duck meat.Cooking weight loss is related to the pH of the meat.Acidic meat conditions will reduce cooking weight loss.
Keranji fruit contains organic acids that can cause the pH of the meat to decrease, thus affecting cooking weight loss.Organic acids in keranji fruit can absorb water content during the marination process, so cooking weight loss can decrease.Several studies have also found that marinating fruits containing organic acids can reduce cooking weight loss [9].Cooking weight loss in meat normally ranges from 15-40% (Soeparno, 2005) [1].The best marinade is keranji marinade with 20% (D2) and 30% (D3) concentration with 15 minutes of marination time (V1) because it effectively reduces cooking weight loss.A good cooking loss has a low percentage because the nutritional content of the meat that comes out during cooking is small.

Moisture content
The results showed that the average moisture content was highest in samples of duck meat marinated with 20% (D2) and 30% (D3) keranji, while the lowest was in the control sample (D0).The data presented that moisture content in control D0 was significantly different (P<0.05) with duck meat marinated with 10% keranji (D1).Moisture content in the Control sample (D0) was very significantly different (P<0.01)from the samples of duck meat marinated using 20% (D2) and 30% (D3) keranji.Marination time using a mini vacuum tumbler in sample V1 (15 minutes) was not significantly different (P˃0.05) with V2 (30 minutes).Marination using keranji had a very significant effect (P<0.01) on the moisture content of the meat.The results of the DMRT analysis showed no interaction between keranji marinade concentration and marination time using a mini vacuum tumbler on moisture content.The higher concentration of keranji will increase the moisture content of duck meat.
The moisture content of normal meat ranges from 65% to 80% [1].The increase in moisture content can be caused by how the vacuum marinator tumbler works.A mini vacuum tumbler is a marinator tool for soaking and processing meat in a vacuum or negative pressure, which helps the marinade absorb into the duck meat tissue.Duck meat marinated in a mini vacuum tumbler absorbs the marinade solution faster than in normal atmospheric conditions/traditional methods.Increased moisture content will result in soft, flavourful and tender meat.High moisture in meat can increase the growth of spoilage bacteria, reducing meat quality [10].Overall, the moisture content of the meat samples in this study is still within the normal range.

Tenderness
The results showed that the average tenderness was highest in duck meat marinated with 20% (D2) and 30% (D3) keranji at a marination time of 30 minutes (V2) and lowest in control (D0).The data presented that the tenderness in control D0 was significantly different (P<0.05) with duck meat marinated with 10% keranji (D1).Tenderness in the Control sample (D0) was very significantly different (P<0.01)from the duck meat samples marinated using 20% (D2) and 30% (D3) keranji.Marination time using a mini vacuum tumbler in sample V1 (15 minutes) significantly differed from V2 (30 minutes).Marination using keranji had a very significant effect (P<0.01) on the tenderness of the meat of cull ducks.The results of the DMRT analysis showed an interaction between keranji marinade concentration and marination time using a mini vacuum tumbler on tenderness.The higher the concentration of keranji and Marination, the more time using a mini vacuum tumbler will increase the tenderness of duck meat.
The increase in tenderness can occur due to the effect of the citric acid organic acid marinade in keranji fruit that changes the structure of the meat.Marination using keranji causes protein hydrolysis.The meat protein will break down and cause the cathepsin enzyme to activate so that the tenderness increases.The fruit's organic acid can improve the meat's tenderness and texture [11][12].Organic acids can cut the fibre bonds of meat so that the meat is softer.Organic acids in fruits can tenderise meat due to the chemical reaction between organic acids and meat protein tissues.When protein denaturation occurs, the protein structure of the meat will change.Organic acids in keranji fruit will break the bonds in the meat protein structure.Organic acids contained in marinades can also increase water retention in duck meat.This is due to the nature of acid marinades, which can help meat proteins retain more water so that meat marinated in vacuum tumblers and acid solutions becomes softer and not dry during cooking.

Colour
Colour is an important indicator in determining the physicochemical quality of meat.Colour can be tested using tools such as a colourimeter or organoleptic.A high L* (light) value means the meat is bright, but a low L* value means the meat is dark in colour.Colour L has a range of values (0-100).L* colour close to the value (0-49) produces a colour that is not bright; if it is close to the value (50-100), then it is bright [13].The results showed that the average L* value was highest in duck meat marinated with 20% (D2) and 30% (D3) keranji at marination time and lowest in control (D0).The data presented that the L* colour in control D0 was significantly different (P<0.05) with duck meat marinated with 10% keranji (D1).Light (L) colour in Control (D0) sample was very significantly different (P<0.01) with duck meat samples marinated using 20% (D2) and 30% (D3) keranji.Marination time using a mini vacuum tumbler in sample V1 (15 minutes) was not significantly different (P˃0.05) with V2 (30 minutes).Marination using keranji had a very significant effect (P<0.01) on the L* colour of the meat of cull ducks.DMRT analysis showed no interaction between keranji marinade concentration and marination time using a mini vacuum tumbler on L* colour.Acid-based marinade can brighten the colour of meat with the right concentration.The colour of duck meat in the study was in the bright category.
Meat colour a* is a category of green to red and has a value of (+) or (-) with a range of (-120) to (120) [13].The colour test results showed that the colour of a* in control was significantly different (P<0.05) with the 20% keranji marinated sample D2.Colour a* in control was also significantly different (P<0.05) with the sample marinated with 30% keranji D3.The length of marination time using a mini vacuum tumbler did not give a significant effect (P˃0.05).The b* colour with a bluish category also increased.The b* colour of the sample significantly differed from the duck meat samples marinated using 20% (D2) and 30% (D3) keranji.Marination time using a mini vacuum tumbler did not affect the bluish colour (b*).There was no interaction between keranji marinade concentration and marination time using a mini vacuum tumbler.Marination using acids can affect colour because of the chemical reaction between organic acids and myoglobin pigments in meat.Fresh duck meat has a reddish colour that comes from the myoglobin pigment.When marinated, the reaction between acid and myoglobin changes the colour of the meat to a lighter but duller colour.Myoglobin will turn into metamioglobin, which has a paler colour radiance than myoglobin, making the meat look lighter.Discolouration does not affect the safety and quality of the meat to be processed but may affect the organoleptic appearance or colour.

Table 1 .
Quality of marinated duck meat using keranji in a mini vacuum tumbler.