Development and shelf life stability of new products for Pacific saury (Cololabis saira)

Abstract

Pacific saury is a primarily wild-caught fish in Taiwan and contains high amounts of polyunsaturated fatty acids (PUFAs). Therefore, its consumption is encouraged by Taiwanese government due to its high nutrition values and affordable price. In this study, four products, Minced saury with pork, Minced saury with XO sauce, Crispy dried saury, and Saury roll with roe, were developed. Optimization of the processing and ingredients were determined by a group of expert panelists, then by a large group of regular consumers. Total bacterial count, coliform, Escherichia coli, volatile base nitrogen, water content, and water activity were analyzed for shelf-life stability. In addition, the indexes of oil oxidation such as acid values, peroxide, and thiobarbituric acid were determined for the oil quality of products. Compositions of fatty acids and fragrant compounds were also analyzed. All microbial, physicochemical, and oil oxidation indexes of the products complied with the official regulations and industrial standards of Taiwan. Composition of fragrant compounds closely related with sensory characteristics and PUFAs composition were not degraded by the processing and storage. A new brand name, Hsiung-Chou, and the logo were established and the products were contracted to manufacturers for commercial production.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05432-1.

Introduction

Pacific saury (Cololabis saira) is an important wild-caught and commonly consumed fish in Taiwan, Japan, and Korea (Tseng et al. 2014; Yoon et al. 2010) as well as in Russia (Gladyshev et al. 2009). The main fishing areas are the North Pacific Ocean, particularly between the areas from Hokkaido to Alaska (Tseng et al. 2014). The production of Pacific saury in Taiwan ranged from 104,450 to 180,466 tons from 2016 to 2019 (Fisheries Agency, Council of Agriculture, Taiwan 2021), which was among the top three of all offshore fishes and accounted from 19 to 29% of the total production of offshore fishery. However, the value of Pacific saury accounted from 12 to 14% of the offshore fishery in the same period, which were significantly lower than production due to the low price. The major harbor for Pacific saury fishing is Kaohsiung, whose production is more than 90% of the whole production of Taiwan annually. The main fishing season is from June to November. However, more than 50% of Pacific saury is exported since the consumption is usually less than 10 tons (Fisheries Agency 2021).

Pacific saury is an oil-rich fish and contains high amounts of polyunsaturated fatty acids (PUFAs), particularly the ω-3 fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (Gladyshev et al. 2009; Zhang et al. 2018). These PUFAs possess several critical biological functions to human health, particularly for cardiac and nerve systems (Yang et al. 2015; Zhang et al. 2018). Pacific saury commonly consumed as whole fish but the tiny bones and the strong fishery flavor diminish the consuming preference of young generation. Additionally, the popularity of traditional processed products, e. g. cans, decrease gradually. Thus, developing new products are necessary to expend the market, particular for young generation.

Since Pacific saury is available at affordable prices and high in nutrition, official agencies have been encouraging the consumption of Pacific saury, particularly for school lunches. Thus, new products are needed to offer more variety of Pacific saury to promote the consumption. The main focus in developing the new products is to retain not only the delightful flavor and taste but also the high nutrition values of Pacific saury, particularly PUFAs. In addition, aspects of the processing, new ingredients, and storage could affect the microbial and physicochemical properties (Cao et al. 2020; Sallam et al. 2007; Sallam 2008). Therefore, maintaining nutritional values and storage stability are critical for developing new product.

Hence, the objectives of this study was to develop the new products of Pacific saury while maintaining the high amount of PUFAs, appealing sensory characteristics, and to devise a long shelf-life. The planned products included three types, minced, dried, roll with roe, which are absent in the current market. Minced pork is a common meal in Taiwan and adding minced Pacific saury fits the consumer behavior and offers a different flavor and taste. The dried item matches the present trend of snack food; it can be stored and distributed at room temperature. The fish roll with roe targets the high end market and elevates the value of Pacific saury. After determining the flavor of the new products, the shelf-life was established by microbial and physicochemical characteristics, particularly the indexes of oil oxidation. The composition of fatty acids was also analyzed to ensure the new products still contained a high percentage of PUFAs. Fragrant compounds were also analyzed to understand the relationship between sensory and chemical compositions.

Materials and methods

Raw materials and chemicals

Pacific saury was provided by the Kaohsiung Fishermen’s Association (Kaohsiung City, Taiwan) and other ingredients were purchased from local stores. The saury fish used in this study was first grade saury, which was the largest among all grades. All media were purchased from Difco Laboratories (Detroit, MI, USA). The standards for gas chromatography were supplied by Sigma-Aldrich (St. Louis, MO, USA).

Development of the new products and design of brand name and logo

All Pacific saury were transported to the pilot plant of the Department of Seafood Science, National Kaohsiung University of Science and Technology (NKUST), at frozen status and stored in − 20 °C freezers. Before processing, all fish were defrosted by running tap water, eviscerated, then the fine bones were removed completely. The processing procedures for the new products are described below:

1. Minced saury with pork: Saury was fried and cut into small pieces. Pork was minced and pan fried with spices, which included fried red onion, anise, cinnamon, pepperconrn, and pepper. After mixing saury and pork at equal amount, soy sauce and suitable seasoning were added, then stewed for around for 1 h. Thus, large packages (about 3 kg) were designed to be sold frozen. This product was reheated by steam before consumption.

2. Crispy dried saury: Saury was cut into thin pieces, then soaked in a seasoning solution containing sugar, soy sauce, and vinegar. The seasoned pieces were roasted at low temperature (60 °C) for 10 h, then at high temperature (220 °C) for 1–3 min. This was a low water activity product and was designed to be stored, distributed, and sold at ambient temperature.

3. Saury roll with roe: Saury was soaked in lemon water, rolled with a with a toothpick, then roasted for 3–5 min. Roes of shishamo fish and shrimp seasoned with cheese and plum powder were placed into the center of the saury roll. After further roasting at 300 °C for 15–20 min, the toothpick was removed. The rolls were frozen at − 20 °C for storage and distribution. Before consumption, the rolls were re-heated by microwave or oven.

4. Saury with XO sauce: Saury was steamed, then minced. The minced saury was pan fried with spices and XO sauce. The finished products were packed into glass jars and sold directly to consumers.

The reheating parameters for frozen products, Minced saury with pork and Saury roll with roe, were determined by the sensory evaluation after reheating, which showed no observed difference between fresh and rehearing products.

The final recipe and procedures were determined by a group of experts at the Kaohsiung Fishermen’s Association and NKUST. The proportions of saury in the aforementioned products were 22–23%, 81–82%, 75–76, and 47–48%, respectively, in the order from Minced saury with pork to Saury with XO sauce. After a sensory evaluation composed of 20-trained panelists, recipe and procedures were modified. Two promotion events were held and totally around 500–600 people attended. The frozen products were reheated and served. Dried saury was severed directly. The opinions of attendants toward to products were asked verbally and recorded. Small adjustments of taste and texture were conducted based on the feedback of the event attendants. In addition, the Labels of Nutrition Facts of the products were determined by a certificated laboratory. A new brand name and logo were designed by the Department of Industrial Design, NKUST, to promote these products.

Sensory evaluation

During initial development, sensory characteristics were evaluated by the specialists from Kaohsiung Fishermen’s Association and NKUST. Twenty panelists were selected and trained from the Association and NKUST. The same grade of saury fish used in this study was served as the training materials and the standard for each evaluation. After the procedures and ingredients were determined by those specialists, sensory characteristics, including appearance, aroma, sweetness, saltiness, flavor, texture, and overall acceptance were evaluated by 20 trained panelists. Evaluation was conducted on a 1–9 scale, in which 1 and 9 indicated extreme dislike and like, respectively.

Microbial analyses

Microbial quality was shown to be closely related to the shelf life of Pacific saury (Cao et al. 2020). Thus, the populations of mesophilic bacteria, coliform, and Escherichia coli were determined on the standard methods published by the Taiwan Food and Drug Administration (TFDA 2020a; b), Department of Health and Welfare. Twenty-five g of the samples were homogenized with 225 mL of phosphate buffer saline (PBS, pH 7.4). For mesophilic bacteria, the homogenate was decimally serial diluted and 0.1 mL of the suitable dilatant was spread onto duplicate plate count agar (PCA) plates. After incubation at 37 °C for 24 h, populations of mesophilic bacteria (log CFU/g) were determined by the colony numbers on the plates and the dilution. For coliform and E. coli, the method, 3-tube most probable number (MPN), was used (TFDA 2020a, b). One mL of homogenate or dilatant was transferred into 10 mL of Lauryl Sulfate Tryptose (LST) broth. After incubation at 37 °C for 48 h, 1 mL of the LST broth from positive tubes (turbid with gas production) was transferred into the tubes containing 10 mL of brilliant green lactose broth (BGLB) or EC broth at corresponding dilution. BGLB and EC were incubated at 37 °C or 44.5 °C for 48 h, respectively. The number of positive tubes (turbid with gas production) of BGLB was determined as the coliform population (MPN/g) after checking the MPN table. The positive tubes of EC broth were further analyzed by streaking onto Eosin methylene blue (EMB) agar plates. After incubation at 37 °C for 24 h, E. coli population (MPN/g) was determined by the EMB agar plates that showed colonies with typical characteristics and checking with the MPN table.

Physicochemical analyses

Water content and water activity (Aw)

The water content (%) and water activity was determined by an infra-red moisture analyzer (IR-35, Denver Instrument, Denver, CO, USA) and a water activity meter (Serial 4, AquaLab, Pullman, WA, USA). Based on the manufacturer’s instructions, an aluminum dish containing 5 g of ground sample was placed into the moisture analyzer to determine the water content. After 20–30 min at 105 °C, the water content was confirmed. For water activity, a plastic dish containing1 g of ground sample was placed into the water activity meter.

Volatile basic nitrogen (VBN)

VBN is the most commonly used index for seafood freshness and the VBN values of saury samples were determined based on the method of Conway micro-diffusion published by TFDA (2020a; b). VBN was extracted from a 2 g of sample with 2.2% trichloroacetic acid (TCA). The TCA extract solution was placed into the outer chamber of the Conway dish and boric acid was placed into the inner chamber. After incubation for 90 min at 37 °C in order for the boric acid to absorb the VBN, 0.02 N HCl was used to titrate the boric acid. After calculation based on the official formula, VBN values were presented as mg/100 g. When VBN value reaches above 25 mg/100 g, the food is considered non-fresh.

Analyses of oil oxidation: acid value (AV), peroxide value (POV), and thiobarbituric acid value (TBA)

The procedures and standards of these analyses were based on the Certificated National Standards (CNS 2011a; b) of Taiwan. For AV, 5 g of sample was extracted by ethanol/ether solution, then titrated with 0.1 KOH. For POV, 5 g of sample was extracted by acetic acid/isooctane solution, oxidized with saturated KI solution, then titrated with sodium thiosulfate. For TBA, 10 g of sample was dissolved in 0.1 N HCl solution. After distilled by a standard device, the distillate was collected and reacted with tetraethoxy propane (TEP) in boiling water for 30 min. The concentration of TBA was determined by the absorbance at 532 nm in a spectrophotometer (Genesys 10S, Thermo Scientific, Waltham, MA, USA) and comparing with the standard curve, which obtained from different concentrations of TBA standards (Ministry of Labor 2011). Lower values of these indexes indicated better oil quality. In addition, oil was regarded as over oxidized when AV and POV were above 2.0 mg KOH/g and 10 meq/kg oil, respectively.

Analyses fatty acids and fragrant compounds

Saury samples were cut into fine pieces then mixed with n-hexane:isopropanol (3:2) solution. After being homogenized for 30 s, it was then filtered through a Adcantec® No. 1 filter (Toyo, Tokyo, Japan). The filtrate was placed into a separatory funnel and washed by a saturated solution of anhydrous sodium sulphate to remove the water residue. After repeating three times, the solvent was removed by a vacuum-rotary evaporator (SB-1200, Rikakikai, Tokyo, Japan). Fatty acids were transesterified by heating at 90 °C for 30 min with a solution of methanol:sulphuric acid (20:1, v/v) to form fatty acid methyl esters (FAMEs). A gas chromatography-mass spectrum system (GC/MS 5977B, Agilent, Santa Clara, CA, USA) with a capillary tube (CP7489, 0.25 mm × 100 m) and a flame-ionization detector was used to determine the composition of fatty acids and fragrant compounds (split ratio: 1:1; and injection pore temperature: 250 °C). The column temperature program had an initial temperature of 100 °C, which was maintained for 5 min before being increased to 230 °C at a rate of 4 °C/min; the final temperature was maintained for 30 min. The composition of fatty acids was determined by comparing with standards of fatty acids (Sigma-Aldrich, St. Louis, MO, USA). For fragrant compounds, peaks were identified by mass spectra after comparing them with the databases-NIST17 Mass Spectral Library.

Statistical analysis

Triplicate samples were used for each test and the tests were repeated at least two times. Data were expressed as the average ± standard deviation and one-way analysis of variance (ANOVA) was used to determine the significant difference (p = 0.05). Statistical analyses were conducted by SPSS (version 12.0, St. Armonk, NY, USA).

Results and discussion

Processing of the new products

Four products and the new brand name were developed (Fig. 1). The brand name, Hsiung-Chou, a combination of Kaohsiung and Chou-Dau (Mandarin pronunciation for Pacific saury), was chosen and a corresponding logo was designed for this series of products (Fig. 1). An English Slogan, “Ocean, Nutrition, Taste”, was used. The Japanese pronunciation for this brand name is O-Aki, which is easier for westerners to pronounce when compared to Hsiung-Chou. Due to this reason and as the newly developed products were Japanese styled, O-Aki was also used on the label. Two commercial manufacturers were contracted to produce more than 500 demonstration samples for each product, which were promoted at several events and received mostly positive response. The Nutrition Facts of products are listed in Table 1. Much higher calories and sodium content per 100 g were shown in Crispy dried saury and Saury with XO sauce due to the lower water contents of these two products (Table 2). Since Minced saury with pork was stewed with soy source, salt, and other spices, its sodium content was the highest among all products.

Fig. 1.

The developed products of Pacific saury, A Minced saury and pork; B Crispy dried saury; C Saury roll with roe; D Saury with XO sauce. All products were labeled with the brand name “Hsiung-Chou” in Chinese character

Table 1.

The nutrition facts for the four products

Products/nutrition components	Calories (Kcal)	Protein (g)	Total fat (g)	Saturated fat (g)	Trans fat1 (g)	Carbohydrate2 (g)	Sugar3 (g)	Sodium (mg)
Minced saury and pork	206.9	14.6	13.7	4.10	N.D.	6.3	5.6	715.4
Crispy dried saury	396.1	37.5	21.7	9.12	N.D.	12.7	12.7	622.9
Saury roll with roe	221.0	26.0	13.0	5.68	N.D.	N.D.	N.D.	304.1
Saury with XO sauce	415.3	11.7	29.7	6.50	0.22	25.3	7.4	656.3

The unit was 100 g

¹N.D.: the detection limit is 0.01 g

²N.D.: the detection limit is < 0.1 g

³N.D.: the detection limit is < 0.5 g

Table 2.

The microbial indexes and physicochemical characteristics of the developed products at day 0 and day 60 during storage

Testing	Products
	Minced saury with pork		Crispy dried saury		Saury roll with roe		Saury with XO sauce
Testing day	Day 0	Day 60	Day 0	Day 60	Day 0	Day 60	Day 0	Day 60
Microbial indexes	N.D	N.D	N.D	N.D	N.D	N.D	N.D	N.D
Water activity	0.98 ± 0.01a	0.96 ± 0.02a	0.70 ± 0.00a	0.78 ± 0.01a	0.97 ± 0.02a	0.97 ± 0.00a	0.69 ± 0.01a	0.72 ± 0.01a
Water content (%)	60.04 ± 1.51a	59.09 ± 2.80a	17.81 ± 5.38a	15.06 ± 2.30a	64.76 ± 7.08a	66.41 ± 0.09a	47.46 ± 2.39a	47.79 ± 6.78a
VBN (mg/100 g)	11.76 ± 4.10a	20.24 ± 0.87b	11.70 ± 1.45a	14.22 ± 0.35b	13.73 ± 2.46a	8.20 ± 0.74b	10.56 ± 0.56a	17.85 ± 2.15b
AV (mg KOH/g)	0.50 ± 0.80a	1.30 ± 0.75b	0.75 ± 2.10a	1.70 ± 5.60b	0.50 ± 0.50a	1.10 ± 0.90b	0.59 ± 1.00a	1.57 ± 3.15b
POV (meq/kg)	2.53 ± 2.20a	7.30 ± 1.70b	2.06 ± 1.75a	8.60 ± 2.53b	3.80 ± 2.18a	5.50 ± 2.89b	2.36 ± 5.20a	9.60 ± 1.14b
TBA (µg/g)	3.65 ± 0.02a	3.52 ± 1.02a	6.48 ± 2.30a	6.26 ± 0.57a	5.38 ± 0.83a	5.73 ± 0.36a	0.56 ± 5.56a	0.23 ± 2.22a

Microbial indexes include mesophilic bacteria count (CFU/g), coliform (MPN/g), E. coli (MPN/g) were all non-detected. The detection limit was 10 CFU/g for mesophilic bacteria count and 3 MPN/g for coliform and E. coli, respectively

All microbial indexes and physicochemical characteristics were not significantly different (p < 0.05) after 60-day storage

VBN standard: 25 mg/100 g

AV standard: 2.0 mg KOH/g fat

POV standard: 10 meq/kg oil

Sensory characteristics of the products

All products were well perceived and most of the characteristics were scored above 7.0. Among the products, the highest score for appearance was Saury roll with roe; Minced saury with pork had the highest scores in aroma, sweetness, saltiness, flavor, texture, and general acceptance (Table 2). During the promotion events, most people expressed preference for the Saury with pork, which was suitable to place on top of rice. Since placing seasoned meat on the top of rice is very common in Taiwan, this product fits Taiwan customs. The appearance and taste of Saury rolls were favored by some consumers, who considered it as an excellent dish by itself. Seafood items seasoned with XO sauce are popular in Taiwan. Thus, the appearance of Saury with XO sauce was not unique but consumers liked its distinctive aroma which offered by the special source developed in this study. The similar situation was happened with crispy dried saury, whose appearance was similar with other snack foods. However, consumers preferred its sweetness/saltiness ratio. In addition, no noticeable change was observed after 60-day storage.

Indexes of microbial and physicochemical quality during storage

The indexes of microbial quality and safety including mesophilic bacteria, coliform, and E. coli were all non-detectable for all products up to 60-day storage. The values of water content and activity remained no significant change throughout storage. The water activity of Saury with XO sauce and Crispy dried saury both remained below 0.80, which complied the regulations for food items to be stored at room temperature (TFDA 2014). VBN, the index of seafood freshness, increased gradually during storage but all under the freshness threshold, 25 mg/100 g (TFDA 2020a; b). The highest VBN values were obtained from the products of Minced saury with pork and Saury with XO sauce. These indicated that meat structure damage caused by mincing processing could result in their high VBN values. The indexes of oil quality including AV and POV of all products gradually increased but were all under the limits of regulations up to 60-day storage (Table 3). High AVs at day 60 was obtained from Crispy dried saury and Saury with XO sauce, whose AVs was 1.70 and 1.57 mg KOH/ g, respectively. In addition, both Crispy dried saury and Saury with XO sauce showed the highest POV at 8.60 meq/kg after 60-day storage. However, both the AV and POV were under the regulatory limits, which are 2.0 mg KOH/g and 10 meq/kg, respectively (CNS 2011a; b). The high AVs and POVs of these two products could be caused by the long processing time and room temperature storage. In contrast, TBA, an index for final stage of lipid oxidation, changed insignificantly within 60-day storage.

Table 3.

The sensory evaluation of products

Products	Appearance	Aroma	Sweetness	Saltiness	Flavor	Texture	General acceptance
Minced saury and pork	7.90 ± 0.91b	7.80 ± 1.24b	7.75 ± 1.21a	7.50 ± 1.36a	7.80 ± 1.15c	7.75 ± 1.07c	8.05 ± 0.94b
Crispy dried saury	6.95 ± 1.23a	7.15 ± 1.14a	7.30 ± 1.26a	7.15 ± 1.27a	6.80 ± 1.28a	6.80 ± 1.15a	7.20 ± 1.06a
Saury roll with roe	8.00 ± 0.73c	7.15 ± 1.09a	6.95 ± 1.10b	6.80 ± 1.24b	7.00 ± 1.26b	7.35 ± 0.93b	7.50 ± 0.99a
Saury with XO sauce	7.70 ± 1.17b	7.65 ± 1.31b	6.95 ± 1.43b	6.90 ± 1.45b	7.45 ± 1.23b	7.20 ± 1.06b	7.40 ± 1.35a

The evaluation was conducted by 20 trained panelists

Data in the same column with the same letters were not significantly different (p < 0.05)

Since Pacific saury is a high-fat seafood, the indexes for oil quality and freshness not only are critical for sensory but also for nutrition values. During storage, the sensory characteristics of all products were also not significantly changed (p < 0.05). These results indicated that all products were stable during storage. Since the storage packages and conditions were proved to be suitable for the products, they could be used as for future mass-production and distribution.

Analyses fatty acids and fragrant compounds

Pacific saury contains high amounts of PUFAs as well as DHA and EPA, which both are the most noticeable ones for consumers as well as food industry. Both DHA and EPA were detected in all processed products. However, the amounts of these two PUFAs decreased according to the proportion of saury meat in the products. Among products, the highest reduction of PUFAs, DHA, and EPA was observed in Minced saury and pork, which had the lowest percentage of saury meat. In addition, pork contained high amount of saturated fatty acids and reduced the proportion of PUFAs. Crispy dried saury possessed the highest percentage of PUFAs due to the highest portion of saury meat in the product. It suggested that these two PUFAs were not or damaged or oxidized with processing procedure rather than decreased proportionally with the percentage of saury meat in the processed products (Table 4).

Table 4.

The relative percentages of unsaturated fatty acids (UFAs), DHA, and EPA of Pacific saury products

Products	UFAs (%)	DHA (%)	EPA (%)	Percentage of saury meat in product
Pacific saury	100	100	100
Minced saury and pork	16.36	14.56	15.33	22.07
Crispy dried saury	80.55	78.25	80.15	81.09
Saury roll with roe	70.01	66.68	72.95	75.19
Saury with XO sauce	45.14	44.28	45.61	47.39

DHA: docosahexaenoic, EPA: eicosapentaenoic acid

Relative percentage between Crispy dried saury and Pacific saury was based on dried weight due the low water content (15–17%) of the Crispy dried saury

The major components of fragrant compounds for all products were palmitic acid (hexadecanoic acid), myristic acid (tetradecanoic acid), stearic acid (octadecanoic acid), and vaccenic acid (9-octadecanoic acid) (supplement data). Minced saury and pork contained the highest amount of vaccenic acid among the four products. It also comprised the second highest level of palmitic acid and stearic acid after Saury with XO sauce and Saury roll with roe, respectively. Since vaccenic acid is a mono unsaturated fatty acid and has higher volatility than saturated fatty acids such as palmitic acid, myristic acid, and stearic acid. It offered more aroma and enabled Minced saury and pork to has the highest score for aroma. Moreover, Minced saury and pork had a reasonable presence of other major fractions such as succinic acid, decanoic acid, nonanoic acid, octanoic acid, which also enhanced the aroma score. Correspondingly, this product had the highest scores for aroma and general acceptance.

Crispy dried saury contained high concentrations of vaccenic acid, palmitic acid and stearic acid (in descending order of their concentrations) which was a more balanced composition as compared to other saury products. It also contained low levels of myristic acid.

Saury roll with roe contained maximum concentration of stearic acid among four saury products. Moreover, it also comprised of the third highest level of vaccenic acid and palmitic acid respectively after Minced saury and pork and Crispy dried saury. Saury with XO sauce contained high concentrations of palmitic acid and myristic acid among four saury products. However, vaccenic acid and stearic acids are lower compared to all other saury products. It also comprises of other fatty acids, such as palmitoleic acid, squalene, pentadecane, benzoic acid, dodecanoic acid (lauric acid) etc. Among them, lauric acid possesses pleasant aroma laurel. Palmitoleic acid and squalene are unsaturated acids with higher volatility. Therefore, this product scored the second highest in aroma.

Since PUFAs are closed associated with sensory and nutrition values, several studies focused on the oil oxidation and composition of fatty acids during storage or processing (Baten et al. 2020; Cha et al. 2001; Lee et al. 2008; Cao et al. 2020; Sallam et al. 2007; Sallam 2008; Tsubouchi et al. 1985). Low temperatures were shown to be a key factor to prevent or retard the oxidation of fatty acids (Lee et al. 2008; Cao et al. 2020; Sallam 2008). Lower the temperatures, less quality deterioration. When pacific saury was stored at − 15 °C or − 30 °C, no fatty acid oxidation occurred and sensory quality were well-maintained (Lee et al. 2008). However, quality gradually deteriorated at 4 °C (Lee et al. 2008; Cao et al. 2020). Some processing methods, such as half-dried (Baten et al. 2020), margination (Sallam et al. 2007), or stored in vacuum-packaged (Sallam 2008), retarded the quality deterioration, which including oxidation of fatty acid, VBN, and microbial growth. Similar results were obtained in this study. Among products, Saury roll with roe and Minced saury and pork were vacuum-packaged and stored at frozen temperatures. Crispy dried saury was a dried product. These three products showed lower POV than Saury with XO sauce, which was sterilized and stored at room temperature. Additionally, the composition of fragrant compounds and fatty acids were not different between day 0 and day 60 samples.

The PUFAs of saury was proved to be stable during processing. Common cooking procedures, such as pan-frying or roasting, did not affect the fatty acid composition of saury (Tsubouchi et al. 1985). Recently, Baten et al. (2020) demonstrated the composition of fatty acids were not altered significantly after hot-smoking (70 °C—30 min) then half-dried. In addition, DHA and EPA were stable in the half-dried saury for 30 days at 10 °C. This study also showed PUFAs were stable in the Pacific saury products.

Conclusion

Four products were successfully developed and well received at several promotion events. In addition, they maintained good quality during storage. All indexes including microbial populations, VBN, oil oxidation, and sensory, were all within the limit after 60-day storage. In addition, this is the first report to identify the fragrant compounds of pacific saury products.

Supplementary Information

Below is the link to the electronic supplementary material.

Abbreviations

AV

Acid value

Aw

Water activity

BGLB

Brilliant green lactose broth

DHA

Docosahexaenoic acid

EMB

Eosin methylene blue

EPA

Eicosapentaenoic acid

MPN

Most probable number

NKUST

National Kaohsiung University of Science and Technology

PBS

Phosphate buffer saline

PCA

Plate count agar

POV

Peroxide value

PUFAs

Polyunsaturated fatty acids

TBA

Thiobarbituric acid value

TFDA

Taiwan Food and Drug Administration

VBN

Volatile basic nitrogen

XO

Extra old

Authors’ contributions

C-CH-conceptualization, data collecting and promotion events; C-YH-chemical analyses, conceptualization, data collecting, and original draft; AKP-chemical analyses, original draft; TK-logo and package design; C-HS-product design and processing; C-MY-liaison between NKUST, Fishermen’ Association, and the Funding Agency; PCC-product design and processing; K-MW-product design and processing; C-DD-for final revision of manuscript; C-ML-conceptualization, program management, final draft.

Funding

This research was funded by the Fisheries Agency, Council of Agriculture (COA), Taiwan, ROC, under the grant numbers 09-agricultural science-1.2.2-fishery-F1.

Availability of data and materials

Not applicable.

Code availability

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Declarations

Conflict of interest

The authors declare that they have no conflict of interest.

Ethics approval

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Consent to participate

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Consent for publication

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