Off-flavors generated during long-term ambient storage of pasteurized drinking yogurt from skim milk.

Few studies have examined sensory quality changes during the storage of pasteurized drinking yogurt (PDY), and the cause of off-flavor development is unclear. Off-flavors generated during 90-d ambient storage (25 °C) of PDY from reconstituted skim milk were investigated by sensory evaluation, volatile component analysis with gas chromatography-mass spectroscopy, and gas chromatography-olfactometry. Rancid off-flavor was induced by increased fatty acid concentration due to fat decomposition by heat-stable lipase. Masking of off-flavors was inhibited by degradation of diacetyl, which originally contributed to yogurt-like flavors. Maillard reaction particular to ambient storage of PDY resulted in changes in the furaneol and sotolon levels, which may be involved in enhancement of off-flavors. Finally, our findings indicated that production of 4-vinylguaiacol may be involved in off-flavor development. The results of this study will contribute to the development of PDY with a longer shelf life and superior flavor.

Impact of High-Pressure Processing on Antioxidant Activity during Storage of Fruits and Fruit Products: A Review.

Fruits and fruit products are an essential part of the human diet. Their health benefits are directly related to their content of valuable bioactive compounds, such as polyphenols, anthocyanins, or vitamins. Heat treatments allow the production of stable and safe products; however, their sensory quality and chemical composition are subject to significant negative changes. The use of emerging non-thermal technologies, such as HPP (High Pressure Processing), has the potential to inactivate the microbial load while exerting minimal effects on the nutritional and organoleptic properties of food products. HPP is an adequate alternative to heat treatments and simultaneously achieves the purposes of preservation and maintenance of freshness characteristics and health benefits of the final products. However, compounds responsible for antioxidant activity can be significantly affected during treatment and storage of HPP-processed products. Therefore, this article reviews the effect of HPP treatment and subsequent storage on the antioxidant activity (oxygen radical absorbance capacity (ORAC) assay), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity assay, ferric reducing antioxidant power (FRAP) assay, 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity assay or Trolox equivalent antioxidant capacity (TEAC) assay), and on the total phenolic, flavonoid, carotenoid, anthocyanin and vitamin contents of fruits and different processed fruit-based products.

Validation of leaf and microbial pectinases: commercial launching of a new platform technology.

Almost all current genetically modified plant commercial products are derived from seeds. The first protein product made in leaves for commercial use is reported here. Leaf pectinases are validated here with eight liquid commercial microbial enzyme products for textile or juice industry applications. Leaf pectinases are functional in broad pH/temperature ranges as crude leaf extracts, while most commercial enzyme products showed significant loss at alkaline pH or higher temperature, essential for various textile applications. In contrast to commercial liquid enzymes requiring cold storage/transportation, leaf pectinase powder was stored up to 16 months at ambient temperature without loss of enzyme activity. Commercial pectinase products showed much higher enzyme protein PAGE than crude leaf extracts with comparable enzyme activity without protease inhibitors. Natural cotton fibre does not absorb water due to hydrophobic nature of waxes and pectins. After bioscouring with pectinase, measurement of contact-angle water droplet absorption by the FAMAS videos showed 33 or 63 (leaf pectinase), 61 or 64 (commercial pectinase) milliseconds, well below the 10-second industry requirements. First marker-free lettuce plants expressing pectinases were also created by removal of the antibiotic resistance aadA gene. Leaf pectinase powder efficiently clarified orange juice pulp similar to several microbial enzyme products. Commercial pilot scale biomass production of tobacco leaves expressing different pectinases showed that hydroponic growth at Fraunhofer yielded 10 times lower leaf biomass per plant than soil-grown plants in the greenhouse. Pectinase enzyme yield from the greenhouse plants was double that of Fraunhofer. Thus, this leaf-production platform offers a novel, low-cost approach for enzyme production by elimination of fermentation, purification, concentration, formulation and cold chain.

Validation of leaf enzymes in the detergent and textile industries: launching of a new platform technology.

Chemical catalysts are being replaced by biocatalysts in almost all industrial applications due to environmental concerns, thereby increasing their demand. Enzymes used in current industries are produced in microbial systems or plant seeds. We report here five newly launched leaf-enzyme products and their validation with 15 commercial microbial-enzyme products, for detergent or textile industries. Enzymes expressed in chloroplasts are functional at broad pH/temperature ranges as crude-leaf extracts, while most purified commercial enzymes showed significant loss at alkaline pH or higher temperature, required for broad range commercial applications. In contrast to commercial liquid enzymes requiring cold storage/transportation, chloroplast enzymes as a leaf powder can be stored up to 16 months at ambient temperature without loss of enzyme activity. Chloroplast-derived enzymes are stable in crude-leaf extracts without addition of protease inhibitors. Leaf lipase/mannanase crude extracts removed chocolate or mustard oil stains effectively at both low and high temperatures. Moreover, leaf lipase or mannanase crude-extracts removed stain more efficiently at 70 °C than commercial microbial enzymes (<10% activity). Endoglucanase and exoglucanase in crude leaf extracts removed dye efficiently from denim surface and depilled knitted fabric by removal of horizontal fibre strands. Due to an increased demand for enzymes in the food industry, marker-free lettuce plants expressing lipase or cellobiohydrolase were created for the first time and site-specific transgene integration/homoplasmy was confirmed by Southern blots. Thus, leaf-production platform offers a novel low-cost approach by the elimination of fermentation, purification, concentration, formulation and cold-chain storage/transportation. This is the first report of commercially launched protein products made in leaves and validated with current commercial products.

Tree age affects physicochemical, functional quality and storability of Amrapali mango (Mangifera indica L.) fruits.

BACKGROUND: The effect of tree age on physicochemical quality attributes and storage behaviour of Amrapali mango fruit was evaluated. Physiologically mature fruits were harvested from 6-, 18- and 30-year-old trees and kept for ripening under ambient conditions (temperature 35 ± 3 °C, relative humidity 60 ± 5%). Observations were recorded at 3-day intervals. RESULTS: Highest total soluble solids and total sugars were found in the fruit sourced from 18-year-old trees. At the end of storage, least titratable acidity (0.17%) and higher carotenoids (10.86 mg 100 g-1 ) were found in 30-year-old tree fruits during the last day of storage. Highest total phenols (TP) (251.33 µg gallic acid g-1 ), antioxidant capacity (AC) (5.63 µmol Trolox g-1 ) and ascorbic acid (AA) (31.13 mg 100 g-1 ) were reported in fruits from younger trees of 6 years old. Maximum respiratory and ethylene evolution peak was observed in fruits obtained from oldest trees, whereas least activities of pectin methyl esterase (0.31 µmol min-1 g-1 fresh weight) and polygalacturonase (53.67 µg galacturonic acid g-1 h-1 ) were observed in 6-year-old tree fruits at the end of the 9-day storage period. CONCLUSION: Higher total soluble solids and total sugars were found in fruit harvested from middle-age-group (18-year-old) trees during the entire storage period of 9 days. Most of the functional parameters, such as TP, AC and AA, were observed to be higher in fruits from younger (6-year-old) trees. The obtained results revealed that produce from middle-age-group (18-year-old) Amrapali mango orchards suit consumers' and processors' requirements. © 2017 Society of Chemical Industry.

Effect of calcium chloride treatments on calcium content, anthracnose severity and antioxidant activity in papaya fruit during ambient storage.

BACKGROUND: There have been no reports on the effects of preharvest calcium application on anthracnose disease severity, antioxidant activity and cellular changes during ambient storage of papaya, and therefore the objective of this study was to investigate these effects. RESULTS: Higher calcium concentrations (1.5 and 2% w/v) increased calcium concentration in the peel and pulp tissues, maintained firmness, and reduced anthracnose incidence and severity. While leakage of calcium-treated fruit was lower for 1.5 and 2% calcium treatments compared to the control, microscopic results confirmed that pulp cell wall thickness was higher after 6 days in storage, for the 2% calcium treatment compared to the control. Calcium-treated fruit also had higher total antioxidant activity and total phenolic compounds during storage. CONCLUSION: Calcium chloride, especially at higher concentrations, is effective in maintaining papaya fruit quality during ambient storage. © 2015 Society of Chemical Industry.

"Effect of sorbic acid on the storage quality of Kaladhi-an acid coagulated milk product".

The present study was conducted to determine the effect of three different levels of sorbic acid (0.1 %, 0.2 % and 0.3 %) on the shelf life and storage quality of Kaladhi. Kaladhi was prepared from pasteurized buffalo milk standardized to 6 % fat and 9 % SNF with coagulation at 40 °C using 5 % lactic acid as a coagulant. Kaladhi prepared without sorbic acid served as control and was compared with the products treated with different levels of sorbic acid for a storage period of 35 days at ambient temperature. The results showed a significant (P < 0.05) effect of sorbic acid on most of the physicochemical parameters i.e. titratable acidity, free fatty acid content (% oleic acid) and thiobarbituric acid value which showed a decreasing trend with increasing concentration of sorbic acid. However, a non-significant (P > 0.05) effect of sorbic acid was observed on pH and proximate parameters of the product. Kaladhi treated with 0.3 % sorbic acid retained most desirable physicochemical and sensory properties throughout the storage period hence, was considered the best.

Evaluation of Two Matrices for Long-Term, Ambient Storage of Bacterial DNA.

BACKGROUND: Culture-independent molecular analyses allow researchers to identify diverse microorganisms. This approach requires microbiological DNA repositories. The standard for DNA storage is liquid nitrogen or ultralow freezers. These use large amounts of space, are costly to operate, and could fail. Room temperature DNA storage is a viable alternative. In this study, we investigated storage of bacterial DNA using two ambient storage matrices, Biomatrica DNAstable® Plus and GenTegra® DNA. METHODS: We created crude and clean DNA extracts from five Streptococcus pneumoniae isolates. Extracts were stored at -30°C (our usual DNA storage temperature), 25°C (within the range of temperatures recommended for the products), and 50°C (to simulate longer storage time). Samples were stored at -30°C with no product and dried at 25°C and 50°C with no product, in Biomatrica DNAstable Plus or GenTegra DNA. We analyzed the samples after 0, 1, 2, 4, 8, 16, 32, and 64 weeks using the Nanodrop 1000 to determine the amount of DNA in each aliquot and by real-time PCR for the S. pneumoniae genes lytA and psaA. Using a 50°C storage temperature, we simulated 362 weeks of 25°C storage. RESULTS: The average amount of DNA in aliquots stored with a stabilizing matrix was 103%-116% of the original amount added to the tubes. This is similar to samples stored at -30°C (average 102%-121%). With one exception, samples stored with a stabilizing matrix had no change in lytA or psaA cycle threshold (Ct) value over time (Ct range ≤2.9), similar to samples stored at -30°C (Ct range ≤3.0). Samples stored at 25°C with no stabilizing matrix had Ct ranges of 2.2-5.1. CONCLUSION: DNAstable Plus and GenTegra DNA can protect dried bacterial DNA samples stored at room temperature with similar effectiveness as at -30°C. It is not effective to store bacterial DNA at room temperature without a stabilizing matrix.

Effect of Non-Dairy Food Matrices on the Survival of Probiotic Bacteria during Storage.

The viability of probiotics in non-dairy food products during storage is required to meet content criteria for probiotic products. This study investigated whether non-dairy foods could be matrices for probiotics. Selected probiotic bacteria were coated on non-dairy foods under two storage conditions, and viabilities were assessed. The non-dairy foods were coated with 5-7 log cfu g-1 of Lactobacillus acidophilus ATCC4356T, Lactobacillus plantarum RC30, and Bifidobacterium longum ATCC15707T. The coated non-dairy foods were stored at 20 °C and 20% relative humidity (RH) or 30 °C and 50% RH. Viability of probiotic bacteria was determined after 0, 2, and 4 weeks of storage. B. longum showed the highest survival at week 4 of 6.5-6.7 log cfu g-1 on wheat bran and oat, compared with 3.7-3.9 log cfu g-1 of L. acidophilus and 4.2-4.8 log cfu g-1 of L. plantarum at 20 °C 20% RH. Under the storage conditions of 30 °C 50% RH, survival of 4.5 log cfu g-1 of B. longum was also found on oat and peanut. This was two and four times higher than the population of L. acidophilus and L. plantarum, respectively. The results suggest that probiotics can survive on non-dairy foods under ambient storage conditions. However, the storage conditions, food matrices, and probiotic strains should be carefully chosen to maximize probiotic bacteria survival.

Cellulose Nanocrystal Reinforced Chitosan Coatings for Improving the Storability of Postharvest Pears Under Both Ambient and Cold Storages.

Cellulose nanocrystal (CNC, 0%, 5%, and 10% w/w, in chitosan, dry basis) reinforced 2% chitosan aqueous coatings were evaluated for delaying the ripening and quality deterioration of postharvest green D'Anjou (Pyrus communis L.) and Bartlett (Pyrus communis L.) pears during 3 wk of ambient storage (20 ± 2 °C and 30 ± 2% RH) or 5 mo of cold storage (-1.1 °C and 90% RH), respectively. Ethylene and CO2 production, color, firmness, and internal fruit quality were monitored during both storage conditions. Moisture and gas barrier, antibacterial activity, and surface morphology of the derived films were also evaluated to investigate the mechanisms of delayed fruit ripening and quality deterioration. In the ambient storage study, the 5% CNC reinforced chitosan coating significantly (P < 0.05) delayed green chlorophyll degradation of pear peels, prevented internal browning, reduced senescence scalding, and improved retained fruit firmness. During cold storage, the 5% CNC reinforced chitosan coating showed a competitive effect on delaying fruit postharvest quality deterioration compared to a commercial product (Semperfresh™, Pace International, Wapato, Wash., U.S.A.). The 5% CNC coating strongly adhered to the pear surface, provided a superior gas barrier and a more homogenous matrix in comparison with the other coatings tested. Hence, it was effective in delaying ripening and improving the storability of postharvest pears during both ambient and cold storage.

Survey of Yogurt Powder Storage in Ambient Export Countries A Safety Evaluation Standard Compliance and Comparative Analysis.

Yogurt powder is fermented milk processed in the form of dry yogurt, and has advantages such as stability, storability, convenience, and portability. China and Vietnam are important export target countries because of the increased demand for dairy products. Therefore, we surveyed dairy product standardization in order to establish an export strategy. Lactic acid bacteria counts are unregulated in Korea and Vietnam. In China, lactic acid bacteria counts are regulated at 1×10(6) colony-forming units (CFU)/mL and detected at 6.24±0.33 Log CFU/mL. All three countries have regulated standards for total bacterial counts. In China, total bacterial counts of milk powder are regulated to n=5, c=2, m=50,000, M=200,000 and detected at 6.02±0.12 Log CFU/mL, exceeding the acceptable level. Lactic acid bacterial counts appeared to exceed total bacterial counts. Coliform group counts, Staphylococcus aureus, Listeria monocytogenes, and Salmonella species were not detected. Acidity is not regulated in Korea and Vietnam. In China, acidity was regulated to over 70°T and detected 352.38±10.24°T. pH is unregulated in all three countries. pH was compared to that of general fermented milk, which is 4.2, and that of the sample was 4.28±0.01. Aflatoxin levels are not regulated in Korea and China. In Vietnam, aflatoxin level is regulated at 0.05 ppb. Therefore, all ingredients of the yogurt powder met the safety standards. This data obtained in this study can be used as the basic data in assessing the export quality of yogurt powder.

Effect of ambient storage on the quality characteristics of aerobically packaged fish curls incorporated with different flours.

The present study was conducted to evaluate the effect of ambient storage on the quality attributes of aerobically packaged fish curls incorporated with optimum levels of different flours. The curls were developed by extrusion technology using fish meat (Catla catla). The fish curls containing optimum levels of different flours viz. 20 percent corn flour, 10 percent black gram flour and 10 percent peanut flour were compared with the control snacks containing 30 percent rice flour and assessed for storage quality and shelf life at ambient temperature. The curls were aerobically packaged in LDPE (low density polyethylene) pouches and evaluated for various physicochemical, microbiological and sensory parameters. Mean values of pH of all the curls showed significantly (p < 0.05) decreasing trend with increasing days of storage (6.34 ± 0.01 on day 0 and 5.90 ± 0.005 on day 28 for control samples, 6.41 ± 0.009 on day 0 and 6.11 ± 0.02 on day 28 for corn flour incorporated samples, 6.36 ± 0.01 on day 0 and 6.14 ± 0.01 on day 28 for black gram flour incorporated samples, 6.57 ± 0.007 on day 0 and 6.34 ± 0.01 on day 28 for peanut flour incorporated samples). TBARS (mg malonaldehyde/kg), total plate count (log cfu/g) and yeast and mould count (log cfu/g) for the control as well as treatment samples showed significantly (p < 0.05) increasing trend with storage. Coliform counts (log cfu/g) were not detected until day 28 in all the products. The mean scores of sensory parameters i.e. appearance and colour, flavor, crispiness, texture and overall acceptability for control as well as treatment samples showed significantly (p < 0.05) decreasing trend with storage period. The decrease was significantly (p < 0.05) highest on 21(st) and 28(th) day of storage. The mean values for all the quality and storage parameters up to the day 21 of the storage were within the acceptable limits. Thus, based on various physicochemical and sensory parameters, the curls incorporated with optimum level of different flours were acceptable up to 21 days of ambient storage within the LDPE pouches.