Mass spectrometry-based electric nose system for assessing rice quality during storage at different temperatures

A mass spectrometry-based electronic nose (MS e-nose) was used to measure changes in rice quality during storage at different storage conditions. Rice was stored for 4 months at four different temperatures (0 °C, 20 °C, 30 °C, and 40 °C) and tested for fat acidity, sensory characteristics, and flavor pattern analysis using the MS e-nose. When the rice was stored for long durations at higher temperatures, fat acidity increased and sensory quality was low. Flavor volatile profiles of the rice determined by MS e-nose revealed a tendency for the results to separate into three groups (months 1 + 2, 3, and 4). Volatile profile changes in rice during storage depended on the storage time, regardless of storage temperature. It is likely that the fat acidity and sensory evaluation results, which were related, could be distinguished by their volatile-producing metabolic activities. Accordingly, MS e-nose system was successfully used to screen and qualitatively evaluate stored rice.     

The influence of storage temperature and storage time on color stability,retail properties and case-life of retail-ready beef

Steaks from three different muscles were either vacuum or carbon dioxide packed and stored for up to 24 weeks at three different storage temperatures (−1.5, 2, or 5 °C). Following storage, they were displayed for up to 30 h. CIE color coordinates, the oxidative states of myoglobin and pH were measured and muscle color, surface discoloration, retail appearance, and odor were evaluated prior to storage and during display (0, 1, 2, 4, 6, 24 and 30 h), and/or immediately prior to and following display. Prior to display, pH was negatively related to duration of storage, and samples stored at −1.5 °C had the highest and samples stored at 5 °C, had the lowest pH. Perception of muscle color was influenced by duration of storage and display, but lower storage temperatures appeared to produce a stabilizing effect. Both lightness of muscle color and deoxymyoglobin content were apparently not influenced by storage temperature or duration of storage or display. Both oxymyoglobin (OMB) and redness, as defined by CIE a* values, were lost progressively during storage and display, but this loss was progressively lower as storage temperature decreased. Yellowness of muscle color, as defined by CIE b* values, generally decreased as storage was prolonged, and this decrease was observed more quickly at higher storage temperatures. Surprisingly, b* values were not related to duration of display. Both surface discoloration and metmyoglobin (MMB) content increased progressively during storage and display. Samples stored at 5 °C displayed the most surface discoloration, while samples stored at −1.5 °C contained the least MMB and displayed the least surface discoloration. Retail appearance deteriorated progressively during storage in all samples stored at 2 and 5 °C and in samples stored at −1.5 °C, which were displayed for at least 24 h. Retail appearance also deteriorated progressively during display in samples stored at −1.5 and 2 °C for three weeks or longer and in samples stored at 5 °C for 0 to 15 and 24 weeks. In unstored samples, samples to be stored at −1.5 °C generally received the lowest retail appearance scores, but after prolonged storage and display, samples stored at −1.5 °C received higher retail appearance scores than samples stored at 5 °C, particularly when samples were stored for 12 weeks or longer and displayed for 1 h or more. Odor deteriorated progressively during storage when measured both prior to display and after 30 h of display. In samples stored for three weeks or longer, samples stored at −1.5 °C generally received the lowest odor scores and were perceived to have the least prevalent off-odors. Samples stored at −1.5 °C maintained a retail case-life of 30 h, when stored for up to 17 weeks, while samples stored at 2 and 5 °C maintained a retail case-life of 30 h, when stored for only eight and seven weeks, respectively. Consequently, storage life can be more than doubled by storage at subzero temperatures (−1.5 °C).     

Storage of hybrid rough rice – Consideration of microbial growth kinetics and prediction models

The objective of this study was to determine kinetics of mold growth on popularly grown hybrid long-grain rough rice during storage at conditions that simulate delayed drying and prolonged storage. Three long-grain hybrid rice cultivars, XL753 (2014) and CL XL745 (2014, 2015) and XL760 (2015) conditioned to four different moisture contents (MCs) (12.5%, 16.0%, 19.0%, and 21.0% wet basis) were stored in rough rice form at temperatures ranging from 10 °C to 40 °C for a period of 16 weeks. The study was repeated using rice from two consecutive crop seasons, 2014 and 2015. For all cultivars, a direct relationship between mold counts and rice MC was observed – whereas more complex trends were observed for the effect of temperature and the duration of storage on mold growth. Kinetic models including Baranyi, Weibull, Gompertz, Richard and Buchanan were successfully modified and fitted using non-linear regression and used to predict the mold counts (log₁₀ CFU/g) for varying conditions (correlations = 0.65–0.76). The study concluded that long-grain hybrid rough rice could be stored at low MC levels (≤17%) and moderate temperatures (≤27 °C) for up to 6 weeks without any change in the mold growth profile. However, storing rice at high MC (>17%) for more than 8 weeks, especially at higher (>27 °C) temperatures should be avoided due to the potential for high mold activity leading to loss of the grain quality.     

Lipolysis and Oxidation in Ultra‐High Temperature Milk Depend on Sampling Month,Storage Duration,and Temperature

During storage, some factors (for example, storage duration and temperature) can affect milk stability and consumer acceptability. Thiobarbituric acid reactive substances (TBARSs), lipid classes, and fatty acid profiles in stored ultra‐high temperature (UHT) milk were analyzed to assess the effects of storage time and temperature on lipid oxidation and lipolysis. With storage duration up to 12 months, the milk fat phase was separated and showed high levels of oxidation and lipolysis, manifested as increased levels of TBARS and free fatty acids. High oxidation levels decreased the percentage of unsaturated fatty acids (UFAs) in triacylglycerol and phospholipids. Higher storage temperatures (20, 30, and 37 °C) resulted in a higher degree of fat aggregation, oxidation, and lipolysis compared with refrigerated storage (4 °C). Additionally, sampling month of raw milk (May, July, and November) affected the lipid profiles of UHT milk during storage, with more UFA oxidized in July than in the other 2 months.     

Nutritional changes in maize (Zea mays) during storage at three temperatures

Nutritional changes in maize grains stored at 10, 25 and 45 °C for 6 months were studied. Significant decrease in pH and increase in titratable acidity was observed during storage of maize grains at 25 and 45 °C. Moisture contents of maize grains decreased by 25% at 25 °C and 38% at 45 °C after six months of storage. Total soluble sugars increased by 10.7% at 10 °C and 17.3% at 25 °C, whereas a 39.5% decrease was observed after 6 months storage at 45 °C. Total available lysine and thiamine contents in maize grains decreased by 13 and 9.26% at 25 °C, 16 and 20.4% at 45 °C, respectively, after 6 months of storage. Protein digestibility decreased by 5.19 and 9.0% at 25 and 45 °C, respectively, whereas decrease in starch digestibility was 9.86% at 25 °C and 15.1% at 45 °C on storage of maize grains for 6 months. However, no significant nutritional changes occurred during storage of maize grains at 10 °C.     

Growth and development of Tribolium castaneum (Herbst) on rice flour and brown rice as affected by time and temperature

Tribolium castaneum (Herbst), the red flour beetle, is a cosmopolitan stored product insect that infests a variety of raw grains and processed grain products. Although this pest is prevalent in rice mills, there is a comparative lack of data on growth and development on rice by-products and fractions compared to other grains. In this study, ten mixed-sex adults were exposed on 200 g of either rice flour or brown rice, and populations were assessed after 2, 4, 6, 8, and 10 months at 22, 27, or 32 °C. At 22 °C, the number of adults, pupae and larvae on rice flour and brown rice remained low throughout the 12-month storage period. At 27 °C, the number of adults on rice flour increased to a maximum at 8 months, while adult populations on brown rice remained relatively constant from 2 to 10 months, with few pupae or larvae in the samples. At 32 °C, adult populations on rice flour and brown rice were constant after month 2, with low numbers of pupae and larvae. Adult predation could have accounted for low numbers of pupae and larvae. Using the original 10-month data, populations were projected for an additional 14 months to predict population patterns. Adult numbers showed an increase over time at all temperatures on rice flour and brown rice at 22 °C but numbers seemed to stabilize at 27 and 32 °C. For both diets at 27 and 32 °C, projected pupae and larvae numbers remained steady but low compared to adults. However, populations would not be expected to increase indefinitely because at some point the resources would become limited and populations would crash or decline. Results show T. castaneum can deplete fixed resources such as bags of rice flour or brown rice when temperatures equal or exceed 27 °C.     

Changes in physicochemical properties of organic hulled rice during storage under different conditions

Effects of packaging materials, storage temperatures and time on physicochemical properties of organic hulled red fragrant rice cv. Hom Daeng were investigated. The samples were vacuum-packed in oriented polypropylene/aluminium/linear low-density polyethylene or nylon/linear low-density polyethylene pouches and stored at ambient temperature or 15 °C for up to 12 months. Results from differential scanning calorimetry indicated that onset and peak temperature of gelatinisation of the aged rice samples increased after the 6th month while enthalpy of gelatinisation initially increased and then decreased after the 8th month. Measurements from the Rapid Visco Analyzer revealed that peak viscosity and breakdown of the rice pastes increased within the first 2 months, then decreased after the 6th month, whereas setback gradually increased during storage. Swelling power, at 70 and 90 °C, of the aged samples, tended to decrease after the 4th month. Lower storage temperature retarded those changes while packaging materials did not influence the changes. Changes in thermal and pasting properties of the aged samples were reversed after adding 2-mercaptoethanol. Hence, an increase in disulphide linkages of oryzenin during storage could play a crucial role in altering those properties. Sensory evaluation indicated a significant increase in hardness of the cooked rice prepared from the longer-aged samples (p ? 0.05). However, the cooked rice samples, deriving from the samples stored at ambient temperature for up to 12 months, were still acceptable for Thai consumers.     

Effects of storage conditions and cooking on colour and antioxidant activities of organic pigmented rice

Influences of the conditions of raw rice storage and cooking on parameters related to colour and antioxidant activities of organic hulled red fragrant rice were investigated. Raw rice samples were vacuum‐packed in oriented polypropylene/aluminium/linear low‐density polyethylene or nylon/linear low‐density polyethylene pouches and stored at ambient temperature or 15 °C up to 12 months. Cooked samples were prepared from aged raw samples. Kernel colour, total anthocyanin content (TAC) of acidic methanolic extracts as well as total phenolic content (TPC), reducing power (RP) and radical scavenging activity (RSA) of methanolic extracts and enzymatically digested samples were maintained during 12‐month storage, regardless of packaging materials and storage temperatures. Cooked kernels had larger L value, lower a and b values, and greater TAC (dry basis), comparing with the raw rice. Cooking caused drastic decrease in TPC, RP and RSA of methanolic extracts. Nevertheless, less negative impacts of cooking were found for enzymatically digested samples.     

Impacts of Low and Ultra-Low Temperature Freezing on Retrogradation Properties of Rice Amylopectin During Storage

Amylopectin retrogradation is a serious problem in starch-based ready meals. In the current research, rice amylopectin was frozen by low temperature (−20, −30, and −60°C) and ultra-low temperature (−100°C), and then stored at 4°C for 21 days or at −18°C for up to 5 months to evaluate the retrogradation properties. Amylopectin retrogradation enthalpy of rice was determined by a differential scanning calorimetry. The results showed that low temperature and ultra-low temperature freezing can effectively retard amylopectin retrogradation during the freezing process and during frozen storage (−18°C) for at least 5 months. However, rice amylopectin still retrograded after the freezing process during chill storage at 4°C. The methods of low and ultra-low temperature freezing combined with frozen storage might be potentially very useful for food industry to produce high quality starch-based ready to eat meals.     

Effect of storage temperature on rice thermal properties

Study on the gelatinization kinetics of rice showed that gelatinization process was divided into two steps: swelling of the amorphous region and disruption of the crystalline region. Higher temperature storage (37 °C) resulted in an increase in the breaking point temperature suggesting that energy for the disorder of these two regions of starch in rice stored at 37 °C was higher than the rice stored at 4 °C. Storage-induced changes in rice led to significant increases in DSC peak temperature (p < 0.05) and significantly broadened peak width (p < 0.01) for rice stored at 37 °C compared to rice stored at 4 °C. As the peak temperature of rice stored at 37 °C was not influenced by the “annealing” treatment in contrast with the increased peak temperature of rice stored at 4 °C after the “annealing” treatment, the results indicate that the ageing process (37 °C storage) has already re-ordered the rice grain structure and that the annealing process under these conditions has no further effect on starch thermal properties. Because starches isolated from rice grain stored at 4 °C and 37 °C had similar thermal properties, this implies that the effects of storage on thermal properties are associated with the interactions between starch and non-starch components following storage. The gelatinization endotherm shifted to a lower temperature (p < 0.01) and a narrowed peak width was achieved after cellulase and protease treatments of stored rice, which indicates that the changes in cell wall remnants and proteins are responsible for the changes in rice thermal properties during storage. Scanning electron microscopy was applied to visualize the treatments of cellulase and protease on rice.     

Paddy rice stored under hermetic conditions: The effect of relative humidity,temperature and storage time in suppressing Sitophilus zeamais and impact on rice quality

The aim of this study was to analyse the effect of relative humidity in suppressing Sitophilus zeamais, in paddy rice stored under hermetic conditions, during four and seven months, at different average temperatures, as well as the impact on rice quality.Hermetic bags, GrainPro^® SuperGrainbag^® Farm™, were used to store two rice varieties under three different relative humidities: 67%, 75% and 85% RH, and average temperatures of 14 °C, 17 °C and 24 °C, both monitored by Hobo^® Data loggers, with the probe placed inside the bags. CheckpointII Portable O₂ and CO₂ Gas Analyzer was used to assess gas contents on the top and bottom of each bag. At the end of the trials, paddy samples were collected to estimate water activity (a_w). The rheology behaviour of rice pastes prepared with race flour obtained from the different treatments was also evaluated, using a controlled stress rheometer.The results showed that the response of the stored-product insects changes with environmental conditions, O₂ and CO₂ contents. Other parameters were considered; a_w increased with relative humidity and temperature, but decreased with storage time. The relative humidity played an important role, together with the increase of temperature, in suppressing insect populations. A modified atmosphere was naturally produced inside the hermetic bag, under 85% RH, with low O₂ and high CO₂ contents, at different average temperatures, 14 °C and 17 °C. These results demonstrated that S. zeamais can survive, but has no progeny. Under the same conditions, but at the higher average temperature of 24 °C, S. zeamais attained 100% mortality before producing progeny.The increase on respiration rate, registered by CO₂ increase and O₂ decrease, for higher RH values, reduced the viscoelastic functions and changed the starch gelatinization point of Indica and Japonica rice.The results obtained showed that storing paddy hermetically, at low relative humidity, did not change atmospheric content and maintained the viscoelastic functions of the rice pastes.     

Feasibility of detection of infested rice using an electronic nose

Electronic nose (E-nose) technology has a potential to be used for detecting insects in stored rice. It may provide a new method to detect the insect activity by providing smell prints for the headspace volatiles in rice mass. The objective of this research was to study the feasibility of using E-nose to detect infested rice during the storage process. An E-nose instrument (Cyranose 320) consisting of 32 sensors for detecting the volatile components produced in infested rice was used for this study. Storage rice with moisture content of 11.8 ± 0.3% was used for conducting the tests. The rice samples were infested with different numbers of adult insects, including rice weevil (Sitophilus oryzae), lesser grain borer (Rhyzopertha dominica) and red flour beetle (Tribolium castaneum), in containers containing 1 kg of rice. The samples were stored at temperatures of 15 °C and 30 °C for four weeks. Air samples in the containers were taken for measurements every five days. The data were analyzed using the principal component analysis (PCA) method. The results revealed that the E-nose was not able to distinguish the clean rice and infested rice with lesser grain borer. While the E-nose had high response ability to the volatile components produced by rice weevil and red flour beetle after four weeks of storage. Consequently, the E-nose could discriminate the clean and infested rice with above insects after four weeks of storage at temperature of 30 °C. Additionally, under the aforementioned conditions, the E-nose could not distinguish the clean and infested rice during the first, second and third weeks of storage. The classification accuracy of E-nose for clean and infested rice was low at storage temperature of 15 °C for the tested insets. It can be concluded that the E-nose has the capability to detect infested rice after four weeks of storage.     

Degradation kinetics of rebaudioside A in various buffer solutions

Rebaudioside A is a noncaloric high‐intensity sweetener extracted from Stevia rebaudiana. For it to be used in foods, rebaudioside A needs to be stable during processing and storage. This study evaluated the kinetics of rebaudioside A degradation in 0.02 and 0.1 m citrate and phosphate buffer solutions at pH 3, 5 and 7 stored at 20, 30 and 40 °C for 9 months. At pH 3 and temperatures less than 30 °C, degradation was slow (i.e. less than 6% loss in 6 months) and not affected by buffer type or buffer concentration. At pH 7, the degradation of rebaudioside A increased dramatically in phosphate buffer (losses of up to 25% in 6 months at 30 °C), while remaining relatively slow in citrate buffer (less than 5% loss). The degradation rates at pH 7 increased 2.6 times as the concentration of phosphate buffer increased. For optimum stability of beverages containing rebaudioside A, formulations with lower concentrations of citrate buffer stored at lower temperatures are recommended.     

Effects of chitosan and selenium treatments on retention of membrane integrity of guava (Psidium guajava L.) fruits during storage

The present study showed the effect of chitosan and selenium on membrane lipids and fatty acids of guava fruits during storage. The fruits were treated with selenium (0.02 ppm), chitosan (1.5%), and a combination of both and stored at room temperature (20 ± 2°C) and low temperature (5 ± 2°C). The membrane integrity was assessed by analyzing lipid constituents and fatty acids. Moreover, the activity of lipoxygenase was also determined. The total lipids were decreased in correlation with a reduction of polar and nonpolar lipids. In addition, unsaturation index of fatty acids also decreased by 3.7% and 8.9% at low and room temperatures, respectively. The treated fruits showed reduced lipid peroxidation as indicated by 21% lower activity of lipoxygenase enzyme. However, fruits stored at low temperature maintained 18% more lipids. The combined treatment of selenium and chitosan with low temperature storage was effective in the protection of membrane integrity.     

Storage of spinach juice agglomerates: Physical,flow, structural,and thermal properties

The objective of this study was to investigate how the various storage temperatures affected the physical properties, flow characteristics, microstructure, and glass transition temperature of spinach juice agglomerates. For this purpose, spray-dried spinach juice powders were processed to agglomerates by using a modified fluidized bed dryer (1.6 m/s airflow rate, 60°C drying air temperature, 20 min processing time, and with different binder solutions containing agents as maltodextrin, gum Arabic, and whey powder isolate). The analyses were carried out every month throughout 6 months while the spinach juice agglomerates were stored at temperatures of 4, 20, and 35°C. The results revealed that over the storage time, the moisture content and water activity values of the agglomerates were generally under 11% and 0.6, respectively. The color values generally showed a decreasing trend depending on the storage time. The solubility times of the samples stored at 4°C were longer than those of stored at other storage temperatures. The SJA-GA had the lowest HR and CI values and thus the best flowability properties during all storage times. There was no detectable change in the structures of SJA stored at 20°C according to the storage time. Throughout the storage time, it was discovered that the glass transition temperature of all spinach juice agglomerates was remarkably similar. Overall, the investigation revealed that storage at 35°C for 6 months might be suitable because it delivered the intended outcomes such as greater flowability and cohesiveness, and shorter wettability and solubility times.     

Impacts of storage temperature and rice moisture content on color characteristics of rice from fields with different disease management practices

Rice downgrading due to discoloration in storage presents a significant loss to growers and processors. The objective of this study was to investigate impacts of storage temperature and rice moisture content (MC) on color characteristics of milled hybrid rice (cv. XL 745) from fields with differing production practices. Freshly-harvested rough rice from field plots treated with and without fungicide for rice disease control during production were procured and stored at four MC levels (12.5%, 16%, 19% and 21% wet basis), and at five temperatures (10 °C, 15 °C, 20 °C, 27 °C, 40 °C) for 16 weeks, with samples taken every 2 weeks. Kinetics of mold growth and rice color were determined. It was observed that at 12.5% MC, discoloration was abated across all studied temperatures and treatments until 6 weeks of storage and increased not in excess of 20% thereafter 16 weeks. As the storage MC increased to 16%, discoloration increased and became significantly notable at the highest temperature of 40 °C. By week 16, at 40 °C storage temperature, discoloration increased significantly to 87.9% and 73% for sample lots from fungicide and non-fungicide treated plots, respectively. At the highest MC (21%), increase in rice discoloration was notable as early as after 2 weeks, across all storage temperatures, and continued to increase, especially for the highest storage temperature of 40 °C, to as high as 99.1% and 96.47%, after 16 weeks, for sample lots from fungicide and non-fungicide treated plots, respectively. There was more expression of discoloration patterns on samples stored at the highest temperature of 40 °C compared to that at lower temperatures, for both categories of sample treatments and ranges of studied MCs. Although not yet widely used for rice, this study suggested that cooling technology for rice, may have potential to extend rice storability, especially by retarding discoloration in the first few weeks after harvest.     

Accelerated aging of jasmine brown rice by high-temperature fluidization technique

After being cooked, newly harvested brown rice becomes a pasty mass and swells only slightly. To modify these undesirable brown rice properties, the paddy needs to be stored for at least 3–6 months. However, problems arise since brown rice has short shelf-life (3–6 months) due to accumulation of free fatty acids (FFA) leading to rancidity during storage. In the present study, high-temperature fluidized-bed drying technique in combination with tempering step was tested to alleviate the above-mentioned problems. The quality of rice dried at temperatures of 130 and 150 °C and tempered for 30 up to 120 min was compared to that of brown rice stored at ambient temperature (approximately 30 °C) for 7 months. The experimental results showed that the cooking and eating properties of the fluidized bed dried brown rice, i.e., hardness, solid loss, volume expansion and elongation ratio, changed in a similar fashion to those of the conventionally aged brown rice. The drying temperature and tempering time affected significantly the brown rice properties. The texture of cooked thermally treated brown rice was significantly firmer than that of the conventionally aged brown rice. In addition, it was found for the thermally treated brown rice that the contents of free fatty acids increased only slightly during storage while the glycemic index reduced from high to low-medium level.     

The effect of storage temperature and time on the consistency and color of sterilized processed cheese

The effect of sterilization (117 °C for 20 min) on the color and consistency of processed cheeses was evaluated. The sterilization resulted in a darker shade (darker color) and increased firmness and elasticity of processed cheeses (P < 0.05). During the storage period (24 months) of sterilized processed cheeses, their color as well as consistency changed depending on the temperature tested (8 and 23 °C). The color change of sterilized processed cheeses was more significant at a higher storage temperature (23 °C) in comparison with the products kept at cold storage temperature (8 °C) (P < 0.05). The firmness of sterilized processed cheeses stored at 8 °C increased during the 24 months. The rise in firmness achieved in the products stored at 23 °C was followed by its decrease in the second year of storage.     

Effects of storage period and temperature on the technological properties,starch digestibility,and phenolic compounds of mung beans (Vigna radiata L.)

This study aimed to evaluate the effects of storage period (0, 2, 4, and 6 months) and temperature (15 °C, 25 °C, and 35 °C) on the germination, vigor, technological properties, starch digestion, and phenolic compound content of mung beans. The germination, vigor, protein solubility, inhibition of the ABTS radicals, and the total free and bound phenolic compound content reduced while cooking time, leached solids, and electrical conductivity increased during storage. Minor changes were observed in grains stored at 15 °C. Starch digestion was higher in stored grains than in freshly harvested beans; however, it decreased on increasing the temperature. The content of bound gallic acid, bound chlorogenic acid, free and bound ferulic acid, free and bound rutin, and free and bound quercetin contents reduced after storage. In contrast, the content of bound caffeic acid, bound vanillic acid, bound myricetin, free coumaric acid, and free catechin contents increased after storage at 15 °C. These results suggested that mung beans could be cooled at 15 °C to reduce the detrimental effects of storage and maintain the nutritional value and germination viability.     

Evolution of quality parameters of high pressure processing (HPP) pretreated albacore (Thunnus alalunga) during long-term frozen storage

The aim of this work was to study the application of high pressure processing (HPP) before freezing for maintaining as much as possible the fresh characteristics of albacore steaks after long-term storage. HPP treatments were applied at 200 MPa for 0–6 min. Then, samples were immediately frozen (−20 °C) and stored (−20 °C) for up to 12 months. Once thawed (4 °C; 24 h), weight losses, color, texture, lipid oxidation (TBARS) and salt-soluble protein content were analyzed.After 12 months of frozen storage, 200 MPa for 6 min minimized thawing loss inherent to freezing and frozen storage and decreased TBARS (53.9%) with respect to the control. However, it resulted in changes in color (higher L*, b* and ΔE values) and texture (higher adhesiveness and springiness) and decreased the salt-soluble protein content with respect to non-pretreated samples. Nevertheless, after cooking, there were no differences in color and texture between HPP pretreated fish and the controls.