Survival of Inoculated Vibrio spp., Shigatoxigenic Escherichia coli, Listeria monocytogenes, and Salmonella spp. on Seaweed (Sugar Kelp) During Storage.

Bacteria including Vibrio spp. persist in coastal waters and can contaminate edible seaweeds. Pathogens such as Listeria monocytogenes, shigatoxigenic Escherichia coli (STEC), and Salmonella have been associated with and present serious health risks in minimally processed vegetables including seaweeds. This study evaluated the survival of four pathogens inoculated onto two product forms of sugar kelp subjected to different storage temperatures. The inoculation comprised of a cocktail of two Listeria monocytogenes and STEC strains, two Salmonella serovars, and two Vibrio species. STEC and Vibrio were grown and applied in salt-containing media to simulate preharvest contamination, whereas L. monocytogenes and Salmonella inocula were prepared to simulate postharvest contamination. Samples were stored at 4°C and 10°C for 7 days, and 22°C for 8 h. Microbiological analyses were performed periodically (1, 4, 8, 24 h, etc.) to evaluate the effects of storage temperature on pathogen survival. Pathogen populations decreased under all storage conditions, but survival was greatest for all species at 22°C, with STEC exhibiting significantly less reduction (1.8 log CFU/g) than Salmonella, L. monocytogenes, and Vibrio (3.1, 2.7, and 2.7 log CFU/g, respectively) after storage. The largest population reduction (5.3 log CFU/g) was observed in Vibrio stored at 4°C for 7 days. Regardless of storage temperature, all pathogens remained detectable at the end of the study duration. Results emphasize the need for strict adherence to temperature control for kelp as temperature abuse may support pathogen survival, especially STEC, during storage, and the need for prevention of postharvest contamination, particularly with Salmonella.

Impact of Blanching, Freezing, and Fermentation on Physicochemical, Microbial, and Sensory Quality of Sugar Kelp (Saccharina latissima).

Low seaweed consumption in the West is due to lack of availability and consumer familiarity. In this study, the effects of preservation processes on quality aspects of Saccharina latissima products were assessed. First, a blanching (100 °C for 1 or 3 min) treatment was used to produce seaweed salad. In a second study, effects of blanching, freezing, and fermentation on kelp quality were assessed and processed kelp was used to produce sauerkraut. Blanching significantly decreased (p ≤ 0.05) the instrumental kelp a* value and firmness. The a* value negatively correlated with overall liking of salads. To prepare sauerkraut, raw, raw/frozen (-20 °C), blanched (100 °C, 1 min), or blanched/frozen kelp were mixed with cabbage, salted, inoculated with starter cultures and fermented. Inconsistent trends in L* values, firmness, and fungi enumeration were observed after fermentation. Consumers evaluated kelp salad (n = 100) and sauerkraut (n = 80) for acceptability. Blanched kelp salad had higher hedonic scores than raw kelp salad. A 100% cabbage sauerkraut control and blanched kelp/cabbage blends were compared; kelp blends were similar to control for appearance, color, and texture but were lower for overall acceptability. Results suggest improved quality and enhanced consumer acceptability of seaweed products with use of minimal processing.

Use of Invasive Green Crab Carcinus maenas for Production of a Fermented Condiment.

To control the population of an invasive species of green crab, we investigated the feasibility of producing a fermented crab condiment. Commercial fermented fish condiments were tested to assess variability in the marketplace and to identify targets for lab-fermented sauces. Finely chopped crab was combined with 100 mg g-1, 200 mg g-1, or 300 mg g-1 NaCl, and spontaneously fermented for up to 120 days. Chromatographic analysis revealed that histamine content was not a safety concern as all treatments were below the current U.S. legal threshold (50 mg 100 mL-1). The majority of microbial and physicochemical properties measured within salt level (proteolytic bacterial population, total volatile basic nitrogen (TVBN), amine nitrogen, water activity, moisture, and biogenic amines) were statistically unchanged between days 60 and 120 of fermentation, suggesting that most of the biochemical changes happened early in the fermentation. While the production of a fermented condiment was successful and could represent an opportunity for the valorization of this invasive species, additional work is needed to accelerate the process and further understand the dynamics of the early fermentation stages.

Anti-Hyperglycemic Effects of Green Crab Hydrolysates Derived by Commercially Available Enzymes.

The predation and burrowing activity of invasive green crabs have had detrimental effects on important marine resources and habitats. Our objective is to develop bioactive hydrolysates by enzymatic proteolysis of underutilized green crab. Mechanically separated mince was hydrolyzed with Alcalase, Protamex, Flavourzyme, and Papain (1%) for 60 min. Subsequently, the hydrolysates were introduced to a simulated gastrointestinal digestion model. Selected samples were fractionated by ultrafiltration, and their anti-hyperglycemic effects including α-glucosidase, α-amylase, and dipeptidyl peptidase-IV (DPP-IV) inhibitory activities and glucagon-like 1 (GLP-1) secretory activity were evaluated. The Protamex treatment showed the highest α-glucosidase inhibitory activity (IC50 1.38 ± 0.19 mg/mL) compared to other enzyme treatments and the crab mince control, and its α-amylase inhibitory activity (IC50 11.02 ± 0.69 mg/mL) was lower than its α-glucosidase inhibitory activity. Its GLP-1 secretory activity was approximately four times higher than the positive control (10 mM glutamine). The <3 kD fraction contributed significantly to the anti-hyperglycemic activity of Protamex-derived hydrolysates, and this activity was stable after simulated digestion. Our results suggest that green crab hydrolysates obtained by Protamex treatment have the potential for type 2 diabetes management and could be incorporated in food products as a health-promoting ingredient.

Physicochemical Properties and Consumer Acceptance of High-Pressure Processed, Sous Vide-Cooked Lobster Tails.

Sous vide (SV) and high-pressure processing (HPP) are promising techniques in the development of high-quality seafood products. The objectives of this study were to evaluate the impacts of HPP on the physicochemical quality and consumer acceptance of subsequently SV-cooked lobster tails. Raw shucked lobster tails were processed at 150 or 350 MPa for 5 or 10 min. Subsequently, half were SV cooked to a core temperature of 65 °C/10 min. Texture profile analysis, shear force, color, salt soluble protein content, water-holding capacity (WHC), moisture content, and weight loss were analyzed. Pressurization at 150 MPa/10 min decreased (P < 0.05) the hardness of raw lobsters compared to non-HPP-treated controls. However, 350 MPa for 5 or 10 min increased (P < 0.05) the shear force in raw and SV-cooked samples. HPP increased (P < 0.05) the L* values but did not affect moisture content, WHC, or weight loss of raw or SV-cooked lobsters. Lobsters were subjected to consumer acceptability testing using a 9-point hedonic scale. Although panelists rated the flavor, texture, and overall liking of the 350 MPa/10 min samples higher than the control and 150 MPa/10 min samples, there were no significant differences among treatment means, indicating that physicochemical changes induced by HPP did not affect consumer acceptance. In addition, approximately 84% of panelists reported that the 350 MPa product met their expectations compared to approximately 75% for the control and 150 MPa treatments. These results suggest that HPP has the potential to be applied in combination with SV cooking to produce consumer-acceptable, value-added lobster products. PRACTICAL APPLICATION: Lobsters are an expensive menu item in restaurants. However, they are susceptible to being overcooked using conventional methods, producing a tough and rubbery texture. Sous vide cooking is reported to provide evenly cooked lobsters with a succulent and juicy texture. In this study, lobsters were sous vide cooked to reach a core temperature of 65 °C, and then maintained at that temperature for 10 min. The application of moderate processing pressures to vacuum-packaged raw lobsters prior to SV cooking altered some physicochemical attributes but has the potential to increase the availability of high-quality, minimally processed seafood with good consumer acceptability.

Potential of recovered proteins from invasive green crabs (Carcinus maenas) as a functional food ingredient.

BACKGROUND: Invasive green crabs contain high-quality proteins that have potential as functional ingredients in formulated foods. This study evaluated the functional properties and compositional characteristics of green crab proteins recovered by isoelectric solubilization/precipitation (ISP). RESULTS: Mechanically separated green crab mince (control) was solubilized at pH 2 (PP2) and pH 10 (PP10), then proteins were precipitated at pH 5.5 and subsequently dried. Yield of recovered protein powder was approximately 1.5 times higher for PP2 than for PP10. Compared with the control (230 g kg-1 ), ash content was reduced in PP2 (54 g kg-1 ) and PP10 (23 g kg-1 ) samples. PP2 contained predominantly large-molecular-weight proteins, while small-molecular-weight proteins were distributed in PP10. With regard to functional properties, at pH 7 and 8, solubility of PP10 was significantly higher than that of PP2. At pH 7.5, PP10 exhibited significantly higher emulsifying activity (1482 m2 g-1 ) than PP2 (858 m2 g-1 ) and the control (958 m2 g-1 ). PP2 showed statistically higher gelation activity and had higher L* value than PP10 and the control. CONCLUSION: The results indicate that recovered green crab proteins have functional properties potentially useful for formulated foods, and that these functional properties can be modified by the solubilization pH during the recovery process. © 2018 Society of Chemical Industry.

Impact of post-rigor high pressure processing on the physicochemical and microbial shelf-life of cultured red abalone (Haliotis rufescens).

High pressure processing (HPP) of post-rigor abalone at 300MPa for 10min extended the refrigerated shelf-life to four times that of unprocessed controls. Shucked abalone meats were processed at 100 or 300MPa for 5 or 10min, and stored at 2°C for 35days. Treatments were analyzed for aerobic plate count (APC), total volatile base nitrogen (TVBN), K-value, biogenic amines, color, and texture. APC did not exceed 10(6) and TVBN levels remained below 35mg/100g for 35days for the 300MPa treatments. No biogenic amines were detected in the 300MPa treatments, but putrescine and cadaverine were detected in the control and 100MPa treatments. Color and texture were not affected by HPP or storage time. These results indicate that post-rigor processing at 300MPa for 10min can significantly increase refrigerated shelf-life of abalone without affecting chemical or physical quality characteristics important to consumers.

Effects of rigor status during high-pressure processing on the physical qualities of farm-raised abalone (Haliotis rufescens).

High-pressure processing (HPP) is used to increase meat safety and shelf-life, with conflicting quality effects depending on rigor status during HPP. In the seafood industry, HPP is used to shuck and pasteurize oysters, but its use on abalones has only been minimally evaluated and the effect of rigor status during HPP on abalone quality has not been reported. Farm-raised abalones (Haliotis rufescens) were divided into 12 HPP treatments and 1 unprocessed control treatment. Treatments were processed pre-rigor or post-rigor at 2 pressures (100 and 300 MPa) and 3 processing times (1, 3, and 5 min). The control was analyzed post-rigor. Uniform plugs were cut from adductor and foot meat for texture profile analysis, shear force, and color analysis. Subsamples were used for scanning electron microscopy of muscle ultrastructure. Texture profile analysis revealed that post-rigor processed abalone was significantly (P < 0.05) less firm and chewy than pre-rigor processed irrespective of muscle type, processing time, or pressure. L values increased with pressure to 68.9 at 300 MPa for pre-rigor processed foot, 73.8 for post-rigor processed foot, 90.9 for pre-rigor processed adductor, and 89.0 for post-rigor processed adductor. Scanning electron microscopy images showed fraying of collagen fibers in processed adductor, but did not show pressure-induced compaction of the foot myofibrils. Post-rigor processed abalone meat was more tender than pre-rigor processed meat, and post-rigor processed foot meat was lighter in color than pre-rigor processed foot meat, suggesting that waiting for rigor to resolve prior to processing abalones may improve consumer perceptions of quality and market value.

Oxidative stability and consumer acceptance of fish oil fortified nutrition bars.

UNLABELLED: Oat and soy-based nutrition bars were fortified with 4 levels of fish oil (0, 6, 12, or 18 g per approximately 600 g batch), representing 0%, 20%, 40%, or 60% replacement of canola oil. The commercially available purified fish oil was not emulsified nor encapsulated, and contained tocopherols. Baked nutrition bars were evaluated for proximate composition, water activity, alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic (DHA) content, and consumer acceptance using a 9-point hedonic scale. The bars were sealed in opaque bags and stored in a stability chamber at 25 °C and 50% relative humidity for 10 wk to assess oxidative stability. There were no significant (P > 0.05) differences in proximate composition, water activity, or ALA levels among treatments. EPA and DHA levels were significantly (P < 0.05) different among treatments, averaging 178.1 mg/serving (20-FO), 488.3 mg/serving (40-FO), and 664.6 mg/serving (60-FO), but none changed during storage. Headspace hexanal and propanal levels decreased over time but were not significantly different among treatments until week 10. Peroxide values were not significantly different except between the control and 60-FO bars. Low values obtained for these analyses suggest negligible oxidation in the bars. Consumer acceptance scores did not differ significantly between the control and lowest fortification level (20-FO), ranging from 6.4 to 6.6 for aroma, texture, flavor, and overall acceptability. These results suggest that nonemulsified, nonencapsulated fish oil can successfully replace canola oil in intermediate moisture nutrition bars to provide EPA and DHA levels as high as 178 mg/serving without affecting consumer acceptability or oxidative stability. PRACTICAL APPLICATION: Omega-3 fatty acid rich fish oil has been shown to have numerous health benefits, but there are limitations to its use in shelf-stable food products. In this study, nutrition bars were successfully fortified with nonencapsulated, nonemulsified fish oil to deliver 178 mg EPA and DHA per 35 g serving. The fortified bars were oxidatively stable over 10 wk and acceptable to consumers.

Fish oil fortification of soft goat cheese.

UNLABELLED: Soft goat cheese was fortified with four levels of purified fish oil (0, 60, 80, and 100 g fish oil per 3600 g goat milk) prior to curd formation to deliver high levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) per serving. The cheese was evaluated for proximate composition, EPA+DHA content, oxidative stability, color, pH, and consumer acceptability. The cheese was partially vacuum packed and stored at 2 °C for four weeks. The fat content was significantly (p < 0.05) higher in the fortified treatments compared to the control, but was not significantly different among fortified treatments. Likewise, EPA+DHA contents were not significantly different among fortified samples, averaging 127 mg EPA+DHA per 28 g serving. No significant lipid oxidation was detected by thiobarbituric acid reactive substances (TBARS) or hexanal and propanal headspace analyses over the four week refrigerated shelf-life study for any treatments. The fortified cheeses were all liked 'moderately' by consumers (n = 105) for overall acceptability, although the 60 g fortification level did rate significantly higher. The control cheese and the 60 g fortification level had no significant differences in consumer purchase intent. These results demonstrate that fortification levels of up to 127 mg EPA+DHA per serving may be added to soft cheese without negatively affecting shelf-life or consumer purchase intent. PRACTICAL APPLICATION: Omega-3 fatty acids have been shown to have strong associations with health and well-being, and fish oil is a rich source of these fatty acids. In this study, goat cheese was successfully fortified to deliver 127 mg omega-3 fatty acids per 28 g serving without affecting shelf life or consumer purchase intent.

The effectiveness of ozone and acidulant treatments in extending the refrigerated shelf life of fresh-cut potatoes.

The objective of the study was to determine the effectiveness of acidulant dip treatments (with or without aqueous ozone) to reduce enzymatic browning and to extend the shelf life of fresh-cut potato slices during refrigerated storage (4 °C) for 28 d. Potato slices subjected to aqueous ozone (2 ppm) had significantly (P≤ 0.05) higher L-values and lower a-values, but ozone did not appear to have any effect on aerobic plate counts (APCs) or polyphenol oxidase (PPO) activity. NatureSeal (NS) and sodium acid sulfate (SAS) were the most effective acidulant treatments in reducing browning (significantly [P≤ 0.05] higher L-values, lower a-values, and browning index values) regardless of ozone treatment. NS and SAS also had lower PPO activity compared to other treatments on days 0 and 28, and significantly (P≤ 0.05) lower APCs (≤2.00 log CFU/g) over refrigerated storage. Therefore, the SAS treatment was comparable to NS, a commercially available product, and showed promise as an effective antibrowning dip to reduce browning and spoilage in fresh-cut potato products. Practical Application: A 1% SAS dip treatment which included 1% citric and 1% ascorbic acid was found to be an effective antibrowning dip for fresh-cut potatoes along with NatureSeal®'s PS-10, compared to other treatments. They were both effective in maintaining low microbial counts over refrigerated storage. Additionally, aqueous ozone washes (2 ppm) showed significant benefits to reduce browning; however, ozone did not affect microbial counts or PPO enzyme activity. Therefore, the SAS treatment could have potential use in the fruit and vegetable industry to reduce browning and spoilage in fresh-cut potato products.

Influence of dietary genistein levels on tissue genistein deposition and on the physical, chemical, and sensory quality of rainbow trout, Oncorhynchus mykiss.

Genistein, the primary isoflavone in soybean, is one of the chemical components responsible for some of the off-flavors associated with soy-based foods. The potential effects of genistein on the sensory and chemical quality of fish muscle may affect the full utilization of soybean meal as an alternative protein in aquaculture diets. Fingerling trout fed commercial diets containing 0, 500, 1000, or 3000 ppm pure genistein were analyzed after 6 and 12 months of feeding. Genistein was extracted by enzymatic digestions in Tris buffer and quantified by high-performance liquid chromatography. Moisture, fat, protein, ash, and tristimulus color of the fillets were determined. The extent of lipid oxidation occurring in fillets harvested after 12 months of feeding was studied by measurements of thiobarbituric acid reactive substances (TBARS) after 4 and 8 days of refrigerated storage at 4 degrees C. Triangle tests were performed to determine if there were any detectable sensory differences. A dietary genistein content of 3000 ppm led to the deposition of approximately 5.4 pmol of genistein/mg of fillet. Triangle test panelists were unable to detect any significant (p < or = 0.05) differences between the fillets from trout fed the 0 and 3000 ppm genistein concentrations. Moisture, ash, and protein content were influenced by time of harvest, while color was unaffected. TBARS levels on days 4 and 8 were significantly (p < 0.05) higher in the fillets from the 0 ppm genistein level than in fillets from fish fed dietary genistein.