A method for temporary storage and preservation and pretreatment and washing of fresh porphyra haitanensis

Abstract

The application discloses a kind of fresh laver processing in temporary storage and pretreatment wash vegetable bacterium reduction method, in turn include: after harvesting complete fresh laver is placed in 4 ℃ condition and is carried out low temperature temporary storage;Complete fresh laver after temporary storage is washed, when washing, seawater tank is connected into micro-nano bubble and ozone generation system, with 0.85 mg / L ozone water as washing medium, solid-liquid ratio 1:20 (w / v), in 4 ℃ environmental condition and washes 30 min;Complete laver after washing is chopped, and is treated with dehydration;Chopped laver is stored at 4 ℃ and is carried out low temperature temporary storage;The application is through the synergistic effect of washing bacterium reduction and low temperature temporary storage, so that dry laver colony total number is reduced to 5.04~5.18 log CFU / g, coliform group is reduced to 3.34~3.9 log CFU / g, while effectively retaining phycobiliprotein and other nutrient ingredients, keep algal cell structure complete, suitable for dry laver processing whole process quality control.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, and in particular to a method for temporary storage, preservation, and pretreatment of fresh seaweed (Porphyra tenera) for washing and sterilization. Background Technology

[0002] Pyropia yezoensis is an important economic seaweed resource in East Asia, widely used in the processing of flavored seaweed, ready-to-eat laver, and functional seaweed products. Rich in high-quality protein, polysaccharides, vitamins, minerals, and phycobiliproteins, Pyropia yezoensis possesses high nutritional and economic value. However, growing in open marine environments, its surface is easily contaminated with sediment, marine microorganisms, and suspended particles. Furthermore, the complex microstructure of the thallus provides favorable conditions for microbial attachment and accumulation. During harvesting, transportation, and processing, these contaminants can easily lead to an increased initial microbial load in the raw materials, thereby affecting product hygiene, shelf stability, and export safety standards.

[0003] Currently, laver processing enterprises mainly use seawater agitation for raw material cleaning. This method relies primarily on liquid disturbance to desorb mud and impurities, but its effectiveness in removing microorganisms from surface folds and microporous structures is limited, and it easily leads to nutrient loss. Furthermore, laver has an ultra-thin leaf-like structure, high water content, and is soft and fragile, making it highly sensitive to mechanical impact and oxidative stress. Many advanced cleaning technologies already used in fruits, vegetables, and aquatic products are difficult to directly transfer to laver processing systems.

[0004] Porphyra yezoensis requires temporary storage after harvesting and after being chopped. Since the harvest season is limited to December to April of the following year, the yield is high during the middle of the harvest, leading to delays in processing and significant quality deterioration during temporary storage. The impact of temperature fluctuations and processing damage on the spoilage process of Porphyra yezoensis is unclear, resulting in processing enterprises lacking effective quality control measures for temporary storage.

[0005] Therefore, establishing a high-efficiency, mild, and industrially applicable method for controlling the quality of laver throughout the entire process from cleaning to temporary storage has become an important issue that the laver processing industry urgently needs to address. Summary of the Invention

[0006] The purpose of this invention is to provide a method for temporary storage, preservation, and pre-treatment washing and sterilization in the processing of fresh laver, aiming to solve the problems of low sterilization efficiency, serious nutrient loss, and significant damage to algal structure in existing washing methods; rapid quality deterioration of laver during temporary storage and lack of effective preservation methods; and lack of coordinated control between washing and temporary storage, making it difficult to guarantee the quality of the entire process.

[0007] The objective of this invention is achieved as follows: a method for temporary storage, preservation, and pre-treatment (washing and sterilization) of fresh laver in processing, comprising the following steps:

[0008] (1) Place the harvested whole fresh seaweed at 4℃ for low-temperature temporary storage;

[0009] (2) Clean the whole fresh seaweed after temporary storage in step (1). When cleaning, connect the seawater tank to the micro-nano bubble and ozone generation system, use 0.85 mg / L ozone water as the cleaning medium, and the material-liquid ratio is 1:20 (w / v). Clean for 30 min under 4℃ environment conditions.

[0010] (3) Chop the whole striped laver after cleaning in step (2) and dehydrate it;

[0011] (4) The striped laver after step (3) is chopped and stored at a low temperature of 4°C.

[0012] As a further preferred embodiment of the present invention, in step (1), food-grade organic acid is used to adjust the pH to 5.5~6.0 for low-temperature acidification and temporary storage.

[0013] As a further preferred embodiment of the present invention, the organic acid used to adjust the pH is food-grade lactic acid or citric acid, wherein lactic acid has a better inhibitory effect on protease and lipoxygenase than citric acid.

[0014] As a further preferred embodiment of the present invention, after cleaning in step (2), the total number of colonies of dried Porphyra stripes is reduced to 5.04~5.18 log CFU / g.

[0015] As a further preferred embodiment of the present invention, in step (4), the lactic acid content in the chopped seaweed increases to 50~70 μmol / g.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. Micro- and nano-bubbles can significantly improve the solubility and stability of ozone. The local physical effects generated during bubble disintegration and the oxidation of ozone form a synergistic enhancement mechanism. Under the conditions of ozone water concentration of 0.85 mg / L and washing for 30 min, the total bacterial count of dried Porphyra stripes decreased from 5.81~6.08 log CFU / g to 5.04~5.18 log CFU / g.

[0018] 2. Compared with traditional stirring and ultrasonic treatment, the method of this invention results in lower levels of protein and phycobiliprotein dissolution in the cleaning solution, and the algal tissue structure remains more intact. Scanning electron microscopy (SEM) observation results show that the combined treatment can effectively reduce impurities and microorganisms attached to the algal surface, while not causing significant tissue collapse or breakage.

[0019] 3-4℃ low temperature is maintained throughout the entire cleaning and temporary storage process. Studies have shown that increased temperature significantly promotes the proliferation of microorganisms in laver, and storage at 4℃ can significantly reduce the proliferation rate of total bacterial count, coliform bacteria, and Pseudomonas.

[0020] 4. Two temporary storage methods are provided for whole laver and chopped laver: exogenous acidification and endogenous acidification. For whole laver, the pH can be adjusted to 5.5-6.0 with organic acids (preferably lactic acid or citric acid, with lactic acid being more effective), inhibiting the activity of endogenous proteases and lipoxygenases. For chopped laver, the release of carbon sources drives microorganisms to shift towards carbohydrate metabolism, producing lactic acid that naturally lowers the pH of the system to 5.5-6.0, thereby delaying protein degradation and lipid oxidation.

[0021] 5. This invention forms a complete technical chain from cleaning and sterilization to low-temperature temporary storage, solving the quality control problems in the pretreatment and temporary storage stages of seaweed processing, and has good prospects for industrial application. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the technical description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a process flow diagram of the present invention.

[0024] Figure 2 A comparison of the total bacterial count of *Porphyra tenuifolia* after different cleaning treatments.

[0025] Figure 3 Comparison of the amount of mud and sand removed from *Porphyra tenuifolia* after different cleaning treatments.

[0026] Figure 4 A comparison chart showing the protein content (mg / mL) in the cleaning solution after different cleaning treatments.

[0027] Figure 5 A comparison of the phycoerythrin (PE) and phycocyanin (PC) content in the thallus of *Porphyra tenuifolia* under different cleaning treatments and in the cleaning solution.

[0028] OW PE in laver: phycoerythrin content in algae within the ozone water treatment group;

[0029] OW PC in laver: phycocyanin content in algae within the ozone water treatment group;

[0030] EW PE in laver: Phycocyanin content in algae within the electrolyzed water treatment group;

[0031] EW PC in laver: Phycocyanin content in algae within the electrolyzed water treatment group.

[0032] Figure 6 Optical microscope (left) and scanning electron microscope (right) images of the morphology of *Porphyra yezoensis* after different cleaning treatments.

[0033] Figure 7 The graph shows the changes in total bacterial count and coliform count of dried Porphyra stripes under conventional stirring and washing (MA) and MNBs+OW treatments during a continuous 7-day simulated processing experiment.

[0034] Figure 8 This graph shows the changes in microbial numbers in whole laver (HL) and chopped laver (SL) after harvest at different storage temperatures and times.

[0035] Figure 9 The graph shows the changes in pH, lactic acid, and K value during the storage of whole laver (HL) and chopped laver (SL) after harvest.

[0036] Figure 10 This is a graph showing the changes in quality deterioration indicators of whole laver (HL) and chopped laver (SL) during storage after harvest.

[0037] Figure 11 Figure showing the effect of acidification treatment on the spoilage process of whole laver (HL) and chopped laver (SL) after harvest. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0039] like Figure 1As shown, the temporary storage, preservation, and pretreatment washing and sterilization method for processing fresh laver of the present invention includes the following steps: the harvested whole fresh laver first enters a low-temperature temporary storage process at 4°C; after temporary storage, it is sent to a cleaning system, and a seawater tank is connected to a micro-nano bubble and ozone generation system, using micro-nano bubbles combined with ozone water for sterilization and cleaning; the cleaned whole laver is chopped by a chopper and dehydrated; finally, the chopped laver is placed in a low-temperature environment at 4°C for temporary storage and later use.

[0040] Example 1: Establishment and optimization of a micro / nano bubble combined with ozone water cleaning process

[0041] This embodiment is used to screen the optimal process parameters for cleaning with micro / nano bubbles combined with ozone water.

[0042] 1.1 Comparison of Single Physical Cleaning Methods

[0043] Fresh *Porphyra tenuifolia* were subjected to conventional stirring cleaning (MA), 40 kHz ultrasonic cleaning (US40), 53 kHz ultrasonic cleaning (US53), and single micro / nano bubble cleaning (MNBs) for 20 min each, with a material-to-liquid ratio of 1:20 (w / v). Unwashed samples served as the control group (CK). The total bacterial count of *Porphyra tenuifolia* in each treatment group was determined.

[0044] Experimental results are as follows Figure 2 As shown in subfigure (a), the unwashed control group had the highest total bacterial count, with a mean of approximately 4.90 log CFU / g. Traditional stirring and cleaning had limited sterilization capacity. The two ultrasonic treatments were superior to stirring and cleaning in terms of sterilization effect, with the total bacterial count after 40 kHz ultrasonic cleaning being 3.43 log CFU / g and after 53 kHz ultrasonic cleaning being 3.80 log CFU / g. The single micro-nano bubble cleaning treatment group had the lowest total bacterial count, at only 3.17 log CFU / g, achieving a bacterial count reduction of 1.73 log CFU / g compared to the unwashed control group, which was significantly better than traditional stirring and ultrasonic cleaning (P<0.05). Based on these results, micro-nano bubbles were selected as the basic cleaning method.

[0045] 1.2 Optimization of cleaning time for micro / nano bubbles

[0046] Single micro-nano bubble cleaning was used, and the cleaning time was set to 0, 10, 20, 30, 60 and 120 min. The total number of colonies at each time point was measured.

[0047] Experimental results are as follows Figure 2As shown in subfigure (b): at 0 min, the bacterial count of the unwashed raw material was 4.43 log CFU / g; at 10 min, it was 4.3 log CFU / g, showing no significant difference from the raw material; at 20 min, it was 3.33 log CFU / g; and after 30 min, 60 min, and 120 min, it remained between 3.11 and 3.17 log CFU / g. The results indicate that 30 min is the optimal washing time, and further extending the washing time does not significantly improve the sterilization effect.

[0048] 1.3 Optimization of Ozone Water Concentration

[0049] Under a cleaning time of 30 min, ozone water concentration gradients of 0 (single micro / nano bubble control), 0.55, 0.7, 0.85, and 1.15 mg / L were set to investigate the antibacterial effect of the micro / nano bubble combined with ozone water system.

[0050] Experimental results are as follows Figure 2 As shown in subfigure (c), the 0 mg / L group had the highest total bacterial count, at 4.36 log CFU / g; the 0.55 mg / L and 0.7 mg / L groups had counts of 4.23 log CFU / g and 4.03 log CFU / g, respectively; when the ozone concentration increased to 0.85–1.15 mg / L, the total bacterial count decreased from 2.94 log CFU / g to 2.63 log CFU / g. Considering the effects of algal damage, protein leakage, and phycobiliprotein loss, 0.85 mg / L was ultimately selected as the optimal process parameter.

[0051] 1.4 Comparison of different cleaning times between micro / nano bubble combined with ozone water and combined with electrolyzed water

[0052] The antibacterial effects of micro-nano bubbles combined with ozone water (0.85 mg / L ozone water) and micro-nano bubbles combined with electrolyzed water (80 ppm available chlorine) were compared under gradient cleaning times of 15, 30, and 45 min.

[0053] Experimental results are as follows Figure 2 As shown in subplot (e), in the unwashed raw material group at 0 min, the initial total bacterial counts of the two groups were 4.94 log CFU / g and 4.92 log CFU / g, respectively. The total bacterial counts in both combined systems showed a pattern of first decreasing and then slightly increasing with increasing washing time. At 30 min, both groups reached their lowest values, with the micro / nano bubble combined with ozone water group at 2.94 log CFU / g, significantly better than the micro / nano bubble combined with electrolyzed water group at 3.09 log CFU / g (P<0.05). At 45 min, the two groups recovered to 2.84 log CFU / g and 3.15 log CFU / g, respectively. Therefore, 30 min was determined to be the optimal washing time.

[0054] 1.5 Comprehensive Comparison of Various Cleaning Processes

[0055] The antibacterial effects of ozone water alone (OW), electrolyzed water alone (EW), micro-nano bubbles alone (MNBs), micro-nano bubbles combined with ozone water (MNBs+OW), and micro-nano bubbles combined with electrolyzed water (MNBs+EW) were compared over a 30-minute cleaning time.

[0056] Experimental results are as follows Figure 2 As shown in subfigure (f), the total bacterial counts after treatment with ozone water alone and electrolyzed water alone were 3.13 log CFU / g and 3.12 log CFU / g, respectively; the single micro / nano bubble group had a count of 4.36 log CFU / g; the micro / nano bubble combined with ozone water group had the lowest total bacterial count, only 2.94 log CFU / g, which was better than the 3.09 log CFU / g of the micro / nano bubble combined with electrolyzed water group. This confirms that 0.85 mg / L ozone water combined with micro / nano bubble washing for 30 min is the pretreatment process with the best sterilization effect in this invention.

[0057] Example 2: The effect of different washing methods on the removal efficiency of silt and sand

[0058] 2.1 Comparison of the mud and sand removal effects of single physical cleaning methods

[0059] Under a cleaning time of 20 min, the removal effects of traditional agitation cleaning (MA), 40 kHz ultrasonic cleaning (US40), 53 kHz ultrasonic cleaning (US53), and single micro / nanobubbles (MNBs) on sediment were compared. The sediment was separated by static centrifugation, dried to constant weight in an oven at 104℃, and then weighed to calculate the sediment mass.

[0060] Experimental results are as follows Figure 3 As shown in (a): the 53 kHz ultrasonic cleaning group had the highest removal amount (19.4 g), followed by the 40 kHz ultrasonic cleaning group (18.56 g), both of which were significantly higher than the traditional stirring cleaning group (4.53 g); the single micro-nano bubble cleaning group had the lowest removal amount, only 3.73 g.

[0061] 2.2 Effect of single micro / nano bubble cleaning time on sediment removal

[0062] like Figure 3As shown in (b), the amount of sediment removed showed a continuous and significant upward trend as the washing time increased from 10 min to 45 min. The removal amounts in the 10 min and 20 min treatment groups were 3.65 g and 3.73 g, respectively; the removal amounts at 30 min and 45 min significantly increased to 15 g and 25 g, respectively, indicating that extending the micro-nano bubble washing time (especially after 20 min) can continuously improve the sediment removal effect.

[0063] 2.3 Effect of Ozone Concentration on Cement Sand Removal Combined with Micro-Nano Bubble and Ozone

[0064] With a fixed cleaning time of 30 minutes, the sediment removal effect under different ozone concentrations (0, 0.55, 0.7, 0.85, 1.15 mg / L) is as follows: Figure 3 As shown in (c), there was no significant difference in the amount of sediment removed from each group, with the sediment deposition ranging from 3.3 to 3.7 g.

[0065] 2.4 Effect of available chlorine concentration on cement sand removal by micro / nano bubble combined electrolysis

[0066] With a fixed cleaning time of 30 minutes and an effective chlorine concentration range of 40–120 ppm, the sediment deposition amount was between 3.78 and 4.16 g. Figure 3 d), no significant difference between groups.

[0067] 2.5 Comparison of sediment removal by two combined systems with different washing times

[0068] like Figure 3 As shown in (e), there was no significant difference in sediment removal between the two combined systems of micro-nano bubble combined with ozone water (MNBs+OW) and micro-nano bubble combined with electrolyzed water (MNBs+EW) at 0 min. When comparing different treatment times, the sediment removal amounts of MNBs+OW at 30 min and 45 min were 3.6 and 3.49 g, respectively, which were significantly lower than those of MNBs+EW (4.3 and 3.9 g).

[0069] 2.6 Comprehensive Comparison of Sediment Removal Capacity of Various Cleaning Processes

[0070] Under the 30-minute condition, there were significant differences in the amount of sediment removed from each group. Figure 3 f). In the 30-minute comprehensive comparison, MNBs+EW removed the highest amount of hair at 4.23g, while MNBs+OW removed 3.48g and OW alone removed 3.49g, which were comparable and better than EW alone removed 3.13g. Figure 3The sediment deposition amounts in experiments a and b differed from those in subsequent experiments, which may be due to the use of different batches of raw materials. Although MNBs+EW showed slightly better sand removal performance, considering the overall efficiency of sterilization, protein retention, and cell integrity, this invention ultimately selected MNBs+OW as the optimal cleaning solution.

[0071] Example 3: The effect of different cleaning methods on protein leakage

[0072] The protein content in the cleaning solution can characterize the degree of damage to algal cells—the higher the amount of protein dissolved, the more severe the damage to the cell membrane structure of *Porphyra tenera* caused by the cleaning treatment.

[0073] 3.1 Comparison of protein leakage under single physical cleaning methods

[0074] There were significant differences in protein leakage among the 20-minute single physical washing groups. Figure 4 a) The 53 kHz ultrasonic cleaning group had the highest protein concentration in the cleaning solution (1.70 mg / mL), followed by the 40 kHz ultrasonic cleaning group (1.63 mg / mL), the conventional stirring cleaning group (1.54 mg / mL), and the micro / nanobubble group (1.04 mg / mL). These results indicate that ultrasonic cavitation easily damages the surface cells of *Porphyra yezoensis*, and cleaning with single micro / nanobubbles minimizes intracellular protein leakage.

[0075] 3.2 Changes in protein leakage of a single micro / nano bubble at different cleaning times

[0076] like Figure 4 As shown in b, as the washing time increased from 10 min to 120 min, the protein content of the washing solution continuously increased from 1.48 mg / mL to 1.58 mg / mL, and the differences between time points were significant (P<0.05).

[0077] 3.3 Effect of ozone concentration on protein leakage

[0078] With a fixed cleaning time of 30 minutes, as the ozone concentration increased (0~1.15 mg / L), the amount of protein leakage first decreased and then slightly increased. Figure 4 c). The highest leakage rate at 0 mg / L (single micro / nano bubble) was 0.49 mg / mL; protein leakage continued to decrease at concentrations of 0.55–0.85 mg / L, reaching a minimum of 0.21 mg / mL at 0.85 mg / L; with further increases in ozone concentration to 1.00–1.15 mg / L, protein leakage rose to 0.21 and 0.25 mg / mL.

[0079] 3.4 Effect of available chlorine concentration on protein leakage

[0080] Results of protein content determination in treatment solutions with different electrolyzed water concentrations (0~120 ppm) Figure 4 d) The results showed that the protein content varied gradually within the range of 0.1 to 0.26 mg / mL in the range of 0 to 60 ppm; it jumped significantly to 0.674 mg / mL at 80 ppm (P<0.05); and increased to 1.597 mg / mL at 120 ppm (P<0.05).

[0081] 3.5 Changes in protein leakage at different washing times in the two combined systems

[0082] like Figure 4 As shown in Figure e, the protein leaching levels in both the micro / nanobubble combined with ozone water (MNBs+OW) and the micro / nanobubble combined with electrolyzed water (MNBs+EW) systems showed a continuous and significant increasing trend with prolonged washing time (P<0.05). The protein content in the micro / nanobubble combined with ozone water system increased from 0.15 mg / mL at 0 min to 0.265 mg / mL at 45 min; the protein content in the micro / nanobubble combined with electrolyzed water system increased from 0.15 mg / mL to 0.3783 mg / mL at 45 min. At 30 and 45 min, the protein content in the micro / nanobubble combined with electrolyzed water group was significantly higher than that in the micro / nanobubble combined with ozone water group (P<0.05).

[0083] 3.6 Comprehensive comparison of protein leakage of various cleaning processes under fixed cleaning duration

[0084] Under 30 min cleaning conditions ( Figure 4 f), the protein content of the single micro / nano bubble (MNBs), single ozone water, and single electrolyzed water groups were 0.182, 0.185, and 0.184 mg / mL, respectively; the combined system of micro / nano bubble combined with ozone water (MNBs+OW) and micro / nano bubble combined with electrolyzed water (MNBs+EW) groups were 0.14 and 0.16 mg / mL, respectively.

[0085] Example 4: Effects of different washing methods on the retention and dissolution of phycobiliproteins

[0086] Phycoerythrin (PE) and phycocyanin (PC) are characteristic functional pigment proteins in Porphyra tenuifolia, and their residual amount in the algae reflects the level of nutrient retention.

[0087] Results of each treatment group under 20 min single physical cleaning conditions are as follows: Figure 5 As shown in a, the residual amounts of PE and PC in the algae of the MNBs group were 0.50 and 0.79 mg / g, respectively, which were significantly higher than those of the US treatment group (p < 0.05), but slightly lower than those of the MA group.

[0088] Comprehensive comparison of various cleaning processes under 30 min conditions ( Figure 5 f) The contents of PE and PC in the algae of the MNBs+OW group were significantly higher than those of the MA and MNBs+EW groups (P<0.05). The dissolution of PE and PC in the cleaning solution was at the lowest level, indicating that MNBs+OW cleaning can retain active ingredients such as phycobiliproteins to the maximum extent while effectively reducing bacteria.

[0089] Example 5: Effects of different cleaning processes on microcellular structure

[0090] The arrangement of algal cells, surface cleanliness, and cell integrity were observed using optical microscopy and scanning electron microscopy (SEM).

[0091] Unwashed control group (CK, Figure 6 a): The cells of Porphyra stripes are tightly arranged, the intercellular spaces are filled with abundant intercellular colloid, the surface of the algae is covered with a large number of mud and sand particles and microbial impurities, the cell outline is intact, and there are no obvious damages or holes.

[0092] Traditional stirring and washing of samples for 2 hours ( Figure 6 b): Surface impurities decreased slightly; as stirring time increased, cell walls contracted and tightened, intercellular spaces increased, and the folds on the algal surface continued to deepen, but cell rupture did not occur throughout the process.

[0093] Samples were ultrasonically cleaned at 53 kHz for 20 min. Figure 6 c): Pores and defects are visible on the surface of the algae, and cracks appear in the cell walls, which induces cell damage. This is consistent with the previous results of protein leakage and large-scale dissolution of phycobiliproteins.

[0094] Cleaning with single micro / nano bubbles (MNBs) for 30 min ( Figure 6 d): Impurities on the algal surface are significantly reduced, cell outlines are clear, and the structure is intact.

[0095] Micro-nano bubbles combined with 0.85 mg / L ozone water (MNBs+OW) for 30 min cleaning Figure 6 e): The algal surface is the cleanest, with mud, sand and microbial deposits basically removed, and the cells are plump, with clear and complete outlines, without obvious wrinkles, holes and cell damage.

[0096] Micro-nano bubbles combined with 80 ppm slightly acidic electrolyzed water (MNBs+EW) for 30 min cleaning Figure 6 f): The overall cleanliness of the algae was good, but cell damage could be observed in the lower left corner of the sample. Its protective effect on the integrity of algal cells was weaker than that of the micro-nano bubble combined with ozone water system.

[0097] Example 6: Continuous 7-day simulated processing test verification

[0098] To evaluate the practical application effect of the optimized process, a continuous 7-day simulated processing test was conducted to compare the effects of traditional stirring and cleaning (MA) with MNBs+OW combined low temperature control (4℃) and standardized disinfection strategy for equipment.

[0099] Two groups were set up: a traditional stirring and washing control group (MA) and a micro / nano bubble combined with ozone water group (MNBs+OW). In the traditional stirring and washing group, 200 g of fresh *Porphyra tenera* was added to 4 L of tap water and stirred for 30 min. In the micro / nano bubble combined with ozone water group, 200 g of fresh *Porphyra tenera* was added to 4 L of 0.85 mg / L ozone water and washed at 4℃ for 30 min. After washing, both groups of samples were chopped and then dehydrated. Before each simulation experiment, the surfaces and utensils that came into contact with the *Porphyra tenera* were cleaned with quaternary ammonium salt disinfectant. The dehydrated *Porphyra tenera* underwent a second drying process: the first drying was at 45–55℃ for 2.5 h; the second drying was carried out with a gradient temperature increase (33℃ 60 min → 38℃ 60 min → 45℃ 50 min → 50℃ 40 min → 65℃ 20 min → 70℃ 10 min). After drying, the total bacterial count and coliform count were measured.

[0100] During continuous processing, the total bacterial count of dried *Porphyra tenera* remained relatively stable in both groups, but the MNBs+OW combined control group was significantly lower than the MA group on each production day (p < 0.05). Figure 7 The total bacterial count and coliform count in the MA group were 5.81–6.08 log CFU / g and 4.13–4.36 log CFU / g, respectively, while those in the MNBs+OW combined control group were 5.04–5.18 log CFU / g and 3.34–3.9 log CFU / g, respectively, which were 0.63–1.04 log CFU / g and 0.23–1.02 log CFU / g lower than those in the MA group.

[0101] The results of the color parameter measurement are shown in Table 1.

[0102] As the storage time increased from day 1 to day 7, the lightness (L) value of the traditional stirring and cleaning group gradually increased from 14.08 to 25.65; the redness (a) value slowly increased; the yellowness (b) value showed an overall upward trend; and the total color difference (ΔE) continuously increased from 14.18 to 25.74.

[0103] The lightness (L) value of the micro / nano bubble combined with ozone water (MNBs+OW) group also gradually increased with storage time, reaching a maximum of 25.37 on day 7. Compared with the traditional stirring and cleaning group, the lightness (L) value of the micro / nano bubble combined with ozone water group was significantly higher in the early stage of storage (1~5 days) than that of the traditional stirring and cleaning group during the same period; the redness (a) value was significantly higher throughout the entire process than that of the traditional stirring and cleaning group at the same storage period; the total color difference (ΔE) continued to increase with time, reaching a maximum of 25.76 on day 7.

[0104] Based on the color patterns of the two groups: in the early stage of storage, the lightness (L) of the traditional stirring and cleaning group was significantly lower than that of the micro / nano bubble combined with ozone water group; the micro / nano bubble combined with ozone water group consistently maintained a higher redness (a) value; in the later stage of storage, the lightness (L) of the two groups tended to be similar, and the total color difference (ΔE) level was close. The micro / nano bubble combined with ozone water cleaning process can better preserve phycobiliproteins in algae, therefore the redness of the sample was better than that of the traditional stirring and cleaning sample throughout the storage process.

[0105] Table 1. Changes in color parameters (L*, a*, b*, ΔE) of Porphyra tenuissima under traditional stirring and washing and MNBs+OW treatment over 7 consecutive days.

[0106]

[0107] Data are expressed as mean ± standard error (n=3); different lowercase letters in the same column indicate significant differences between groups (P<0.05). (L*): luminance value; (a*): red-green hue (positive values ​​lean towards red); (b*): yellow-blue hue (positive values ​​lean towards yellow); (△E): total color difference.

[0108] Example 7: Changes in microbial levels during the temporary storage period of fresh *Porphyra tenera* after harvest and after chopping

[0109] This embodiment systematically investigated the microbial changes of whole laver (HL) and chopped laver (SL) after harvest within 0 to 7 days at different storage temperatures (4, 10, 15, 20℃).

[0110] 7.1 Changes in total bacterial count and coliform flora

[0111] Experimental results are as follows Figure 8 As shown in (a~d). The initial total bacterial count and coliform count of whole laver (HL) after harvest were approximately 3.8 log CFU / g and 2.03 log CFU / g, respectively. The total bacterial count and coliform count increased most slowly at 4℃, reaching 5.23 and 3 log CFU / g, respectively, on day 7; while at 15℃, they reached 7.44 and 6.47 log CFU / g, respectively, on day 7.

[0112] 7.2 Changes in the number of Pseudomonas aeruginosa

[0113] like Figure 8As shown in (e-f), the initial Pseudomonas aeruginosa concentration in whole laver (HL) after harvest was approximately 4.65 log CFU / g, and remained at 5.85-6.6 log CFU / g on day 7. In chopped laver (SL), the concentration increased from approximately 3.06 log CFU / g initially at 4°C to 5.07 log CFU / g on day 7; the most rapid increase was observed at 15°C, reaching a peak of 7.07 log CFU / g on day 5.

[0114] Example 8: Changes in pH, lactic acid, and K values ​​of fresh *Porphyra tenuifolia* after harvest and after chopping

[0115] 8.1 pH Changes

[0116] like Figure 9 As shown in (a~b), the pH of the whole laver (HL) group decreased from the initial 6.75 to 6.35 after 7 days of storage at 4℃, and further decreased to approximately 6.18 at 15℃. The pH of the chopped laver (SL) group decreased rapidly to 5.70~5.60 after 2~3 days of storage at 15℃ and 20℃ (P<0.05).

[0117] 8.2 Changes in lactic acid content

[0118] like Figure 9 As shown in (c~d), the lactic acid content of the whole laver (HL) group was generally low after harvest (<20 μmol / g), and gradually decreased with storage time. The lactic acid content of the chopped laver (SL) group rapidly increased to 50~70 μmol / g at 15℃ and 20℃ (P<0.05), consistent with the decreasing trend of pH.

[0119] 8.3 Changes in K value

[0120] like Figure 9 As shown in (e~f), the K value of the whole post-harvest laver (HL) group was 25%~30% within 7 days of storage at 4~10℃, and increased to 30%~35% at 15~20℃. The K value of the chopped laver (SL) group was significantly higher than that of the whole post-harvest laver group.

[0121] Example 9: Changes in the volatile basic nitrogen, protease, thiobarbituric acid reactants, and lipoxygenase activities of fresh *Porphyra tenera* after harvest and after chopping.

[0122] 9.1 Changes in volatile basic nitrogen (TVB-N)

[0123] like Figure 10As shown in (a-b), the volatile basic nitrogen in the whole laver (HL) group remained at 25-30 mg / 100g for 7 days at 4℃; at 15℃ and 20℃, it reached approximately 119 mg / 100g and 144 mg / 100g, respectively, on day 7. In the chopped laver (SL) group, the volatile basic nitrogen remained below 10 mg / 100g at 4-15℃, only slightly increasing to approximately 15.4 mg / 100g on day 7 at 20℃.

[0124] 9.2 Changes in protease activity

[0125] like Figure 10 As shown in (c~d), the protease activity of the whole post-harvest laver (HL) group remained at 1300~1650 U / 100mL for the first 3 days at 4℃, and then decreased to 600~700 U / 100mL; at 15~20℃, it gradually decreased to 500~600 U / 100mL. The protease activity of the chopped laver (SL) group was generally lower than that of the whole post-harvest laver samples, and was about 450~600 U / 100mL throughout the storage period.

[0126] 9.3 Changes in Thiobarbituric Acid Reactives (TBARS)

[0127] like Figure 10 As shown in (e~f), in the whole laver (HL) group after harvest, the thiobarbituric acid reactants increased from approximately 0.62 mg / 100g initially to 4.1 mg / 100g on day 7 at 4℃; and reached 5.9 mg / 100g on day 7 at 15℃. The TBARS values ​​of the chopped laver (SL) group were generally lower than those of the HL group.

[0128] 9.4 Changes in lipoxygenase (LOX) activity

[0129] like Figure 10 As shown in (g~h), the LOX activity of the whole laver (HL) group increased significantly with increasing temperature after harvest, reaching approximately 550 U2 / g on day 7 at 15℃. The LOX activity of the chopped laver (SL) group was generally lower, remaining at 150~300 U2 / g.

[0130] Example 10: Verification of the effect of exogenous acidification treatment on the spoilage process of whole and chopped laver after harvest.

[0131] This embodiment is a further preferred technical solution, namely, based on step (1) of claim 1, food-grade organic acid is used to perform exogenous acidification treatment on whole seaweed to verify its enhancement effect on temporary storage and preservation.

[0132] The pH of whole laver (HL) and chopped laver (SL) after harvest was adjusted to 5.5 using food-grade lactic acid (LA group) and citric acid (CA group), respectively. Tap water treatment was used as the control group (CK, pH about 6.7). The laver was stored in a constant temperature incubator at 15℃ in the dark for 7 days, and various spoilage indicators were measured.

[0133] 10.1 Inhibitory effect on protein degradation

[0134] like Figure 11 As shown in (a-d), the TVB-N in the HL CK group increased sharply with storage time, reaching approximately 112 mg / 100g on day 7, significantly higher than that in the HL CA group (8.4 mg / 100g) and the HL LA group (14 mg / 100g) (P<0.05). The endogenous protease activity in the HL CK group was at a high level (1318 U / 100mL), while the HL CA group (511 U / 100mL) and the HL LA group (501 U / 100mL) significantly inhibited protease activity. These results indicate that exogenous acidification effectively inhibits protein degradation in intact laver, and lactic acid has a better inhibitory effect than citric acid.

[0135] 10.2 Inhibitory effect on lipid oxidation

[0136] like Figure 11 As shown in (e~h), the TBARS content in the HL CK group reached approximately 5.56 mg / 100g on day 7, significantly higher than that in the HL CA group (4.73 mg / 100g) and the HL LA group (4.11 mg / 100g) (P<0.05). The HL CK group exhibited a high level of LOX activity (543 U2 / g), while the HL CA group (341 U2 / g) and the HL LA group (292 U2 / g) significantly inhibited LOX activity. These results indicate that exogenous acidification effectively inhibits lipid oxidation, and lactic acid has a better inhibitory effect on LOX than citric acid.

[0137] The above description is merely a specific embodiment of the present invention, but the scope of protection of the invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the invention.

Claims

1. A method for temporary storage, preservation, and pre-treatment (washing and sterilization) of fresh laver in processing, characterized in that, It includes the following sections in sequence: (1) Place the harvested whole fresh seaweed at 4℃ for low-temperature temporary storage; (2) Clean the whole fresh seaweed after temporary storage in step (1). When cleaning, connect the seawater tank to the micro-nano bubble and ozone generation system, use 0.85 mg / L ozone water as the cleaning medium, and the material-liquid ratio is 1:20 (w / v). Clean for 30 min under 4℃ environment conditions. (3) Chop the whole striped laver after cleaning in step (2) and dehydrate it; (4) The striped laver after step (3) is chopped and stored at a low temperature of 4°C.

2. The method according to claim 1, characterized in that: In step (1), food-grade organic acid is used to adjust the pH to 5.5~6.0 for low-temperature acidification and temporary storage.

3. The method according to claim 2, characterized in that: The organic acids used to adjust the pH are food-grade lactic acid or citric acid, with lactic acid having a better inhibitory effect on proteases and lipoxygenases than citric acid.

4. The method according to claim 1, characterized in that: After cleaning in step (2), the total bacterial count of dried Porphyra stripes is reduced to 5.04~5.18 log CFU / g.

5. The method according to claim 1, characterized in that: In step (4), the lactic acid content in the chopped seaweed increases to 50-70 μmol / g.

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