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Sweetpotatoes (SP) stored for 9-12 mo after harvest were cut into cylindrical pieces and, following factorial experiments and response surface design, were blanched at 50-80°C for 15-274 min. Instrumental textural properties were measured by uniaxial compression and texture profile analysis. Samples of selected blanching treatments were canned in syrup for textural and sensory evaluations. Both blanching temperature and time had significant effects on firmness. Optimal temperature for maximal firmness retention was about 62°C. For canned SP, the 62°C blanched samples were more intact (2-3-fold) and firmer (2-7-fold) than controls. Sensory texture and overall acceptability were greatest for samples blanched at 62°C for 30 or 45 min before canning.

With the increasing demand for freshly cut vegetables, a substantial potential exists in developing minimally processed sweet potato products. This study was undertaken to determine the effects of semipermeable polymeric materials and modified atmosphere packaging (MAP) on quality changes and microbial growth in shredded sweet potatoes under refrigerated storage. Shredded sweet potatoes from two major commercial cultivars (Beauregard and Hernandez) were packed in low and medium O2permeability bags and flushed with gas composed of 5% O2, 4% CO2and 91% N2. Quality changes and microbial growth were monitored in comparison to the samples packed in air using high-O2permeable films. The quality of shredded sweet potatoes could be maintained for 7 days at 4C in air, but extended up to 14 days in MAP. Considering the parameters measured in this investigation, the best results were obtained by MAP using moderately O2-permeable film (7000 cm3/atm/m2/24 h). Shredded sweet potatoes stored in MAP showed less changes in tissue firmness, dry matter, ascorbic acid and starch than shredded sweet potatoes stored in air. The MAP-stored shredded sweet potatoes consistently exhibited fewer total aerobic bacteria and enteric bacteria compared to the shredded sweet potatoes stored in air. Yeasts, molds, lactic acid bacteria, color, beta-carotene and sugars of all stored shredded sweet potatoes did not significantly change, regardless of treatments. Higher ethanol levels were generated in the MAP-stored shredded sweet potatoes after 10 days, but off-odors were not detected in any of the MAP-stored shredded sweet potatoes.

Low-temperature blanching of sweetpotatoes (SP) prior to cooking has been shown to significantly increase firmness retention. This research investigated the effect of blanching on firmness, pectin methylesterase activity (PME), pectin methylation, and galacturonic acid and cell wall material concentrations in SP tissue subjected to blanching and cooking treatments. PME activity decreased 82% after 20 min of blanching in water at 62°C, while sample firmness continued to increase with blanching time (3.5 N for unblanched and 19.0 N for 90 min blanched, and cooked tissue), indicating that firming due to pectin demethylation explains part of the observed increased firmness retention caused by low-temperature blanching, but unknown factors also play a role.

Summary The viscoelastic properties of sweetpotato (SP) puree restructured with alginate were determined and compared with those of non-restructured SP puree. Results from oscillatory shear experiments showed that both purees behaved like a gel with the storage modulus (G′) predominant over the loss modulus (G′′). The addition of a calcium/alginate complex increased the firmness of SP puree. Gel strength of both restructured and non-restructured puree was highest at room temperature (25 °C).

The objectives of this research were to investigate the applicability of using an alginate–calcium gelling system to produce a French fry-type product using high beta-carotene sweetpotato puree as the main ingredient and to compare four instrumental methods of texture measurement for this product type in relation to sensory textural properties. Sweetpotato puree made with Jewel cultivar sweetpotatoes was restructured using optimized alginate–calcium concentrations. A consumer panel scored sweetpotato fries containing 0.35 g alginate/100 g and 0.5 g CaSO4/100 g highest for appearance, texture, flavor, and overall acceptability. A trained texture profile panel described the product with 15 texture notes. Of these attributes, nine sensory notes describing hardness, mastication shear, cohesiveness, springiness, moistness, and oiliness were highly correlated with some instrumental parameters (r=0.79–0.92) for measuring textural properties. The instrumental methods evaluated were instrumental texture profile analysis, three-point bending force, Kramer shear force, and puncture force. Among these instrumental methods, Kramer shear appeared to be the method of choice because of method's simplicity and high precision (coefficient of variation ≤10%).

The objective was to determine the effect of sweet potato (SP) puree preparation methods on the properties of texturized SP products. The treatments were separated into two main types in which sliced SPs were cooked prior to puree preparation, or purees were prepared by grinding raw roots, followed by heat processing using steam injection. Purees from each treatment were texturized into cylinders 12.7 cm long and 5.5 cm in diameter, using an alginate-calcium system, and frozen. We found that cooked purees prepared by steam injection of raw purees had higher viscosities than did purees made from cooked SP. Texture Profile Analysis (TPA) revealed that texturized product made from SP cooked before puree preparation was the most fracturable and least springy of the texturized products. Sensory panelists did not express apreference for texturized product from any of the treatments, but 23% of the panelists noted a grainy texture and/or raw root aroma in products prepared by steam injection of raw purees. In view of these observations and the fact that puree preparation from cooked SP is the simplest process, this process appears to be the best for this type of texturized SP product.

Jewel cultivar SP stored 1, 5, and 10 months after harvest were peeled, cut into pieces, treated, and canned in 15 and 30 deg Brix syrups. Samples were evaluated for degree of disintegration (wholeness), firmness (shear force), chemical composition, and sensory acceptance. Untreated samples (controls) disintegrated as storage time prior to processing increased, while treated samples remained intact; firmness and sensory texture scores declined with increasing storage time. Treated samples were significantly firmer than controls throughout the study, and, although shear force declined over time, sensory panelists did not detect any texture change. Overall sensory acceptance at 10 months was greatest for phosphate-treated samples in 30 deg Brix syrup. Thus, the alkali-neutralization process retains firmness, wholeness, and sensory quality of SP canned after long-term storage. This process will permit commercial processing of SP roots stored for up to 10 months.

Laboratory starches, isolated from seven sweetpotato selections grown at two locations in Peru, and commercially available Peruvian starch were characterized with regard to physicochemical properties. Chemical analyses included determination of nitrogen, ash, and amylose content. Physical characterization was based on results from differential scanning calorimetry (DSC), swelling power, solubility, and rheology of the pastes. We found that nitrogen and amylose content were not affected by location or selection, while ash content was affected by location. Results from the DSC analysis showed that selection identity (SI) did not affect DSC enthalpy, onset, peak, and final temperatures. Location affected only peak temperature. Investigation of starch swelling power showed that SI and location did not affect swelling power above 75°C, and that laboratory starch samples had greater swelling power than commercial samples. Solubility was affected by location, but not by SI. Maximum viscosities of heated starch slurries were not affected by SI or location. Although laboratory and commercial samples did not differ significantly in chemical composition, physical behavior of their pastes was significantly different.

This study compared two instrumental methods, namely uniaxial compression and texture profile analysis (TPA), with sensory evaluation in describing the textural properties of cooked sweetpotatoes. The steamed cooked samples (1.35 × 2.2 cm cylinder) of four cultivars and six selections were subjected to a trained texture profile panel for sensory ratings and the two instrumental methods for determination of the mechanical properties. Factor analysis indicated that the 15 sensory variables were grouped into 3 main factors, namely moistness-firmness (factor 1), particles (factor 2), and fiber (factor 3). Among the instrumental parameters, shear stress of compression and fracturability, hardness, and gumminess of TPA correlated highly (R = 0.73–0.95) with both the mouthfeel and mechanical-type sensory notes. These parameters of the two instrumental methods were linearly related (R2≥ 0.95) and could be converted from one to another with a high degree of reliability. Regression equations based on shear stress significantly explained (R2= 0.71–0.91) eight of the sensory notes. These instrumental parameters can be good predictors of cooked sweetpotato texture.

Strips from five sweetpotato (SP) cultivars (cv.) representing two different texture/flavor types were prepared and frozen. They were fried and their flavor and texture evaluated by sensory panels. Selected physical and compositional analyses were performed on raw and fried SP. An untrained preference panel tended to score the flavor of the sweeter types highest and the texture of the firm types higher than sweet types. A trained profile panel identified and scored flavor notes and texture categories. This research indicated that the intensity of the flavor notes sweetness and starch and the intensity of texture notes first-bite moistness and first-bite hardness were highly correlated with some of the compositional parameters. Correlation between compositional parameters and the flavor and texture note intensities listed above could be developed into a system to predict those sensory properties in newly developed selections without having to resort to sensory analyses. Keywords: Texture profile analysis; ...

A combination of alkali (sodium phosphate or calcium chloride) infiltration and blanching and their order of application were studied for their effect on the sensory and physico-chemical (moisture, fat, sugars, and shear force) quality of sweetpotato French fries (SPFF) made from sweetpotatoes (SP) stored for 3 months or 1 year. Sensory quality (taste, texture, and overall acceptability) were evaluated using a nine-point hedonic scale. Treatment of SP strips with sodium phosphate solutions prior to blanching caused an increase in firmness as compared with untreated strips. For SPFF produced from SP stored 3 months, sensory quality of treated SPFF was indistinguishable from untreated SPFF. However, for SP processed at 1 year of storage, the sensory texture of treated samples was more acceptable than the sensory texture of untreated samples. Shear force data indicated that the firmest samples did not have the most acceptable sensory texture, indicating that there is an optimal level of shear force that gives the “right” amount of resistance to chewing to result in a more acceptable product. This process can be used in the manufacture SPFF from SP stored up to 1 year.

Calcium from a CaCl 2 brine approximately iso-osmotic with cucumber cell sap penetrated cucumber fruit much more slowly than did calcium ions from a Nacl + CaCl 2 brine supra-osmotic with cucumber cell sap. After 96 h calcium that penetrated from the iso-osmotic brine was localized mostly in the exocarp and relatively little in the interior tissues, while calcium that penetrated from the supra-osmotic brine reached higher concentrations and was more evenly distributed among the exocarp, mesocarp, and endocarp sections.

The effect of the emulsifying agents, glycerol monostearate (GMS), sodium steroyl lactylate (SSL), and konjac flour (KF, a texture modifier which releases an aggregated glucomannan polymer in water), on the thermal and physical properties of native, naturally fermented (NF), and mixed-culture fermented (MCF) cassava starches was investigated. GMS and SSL decreased hot water-mediated granule swelling and amylose leaching thereby further increasing internal stability of the starches via formation of an emulsifier−amylose complex and granule surface coating. KF had little effect on the rheological behavior of starch pastes. Both the fermentation process and addition of the emulsifying agents would likely also influence the textural properties of cassava starch or flour pastes. Keywords: Glycerol monostearate; sodium steroyl lactylate; konjac flour; gelatinization; swelling power

Jewel and Beauregard sweetpotatoes were sampled at harvest and after 49, 119, and 217 days of storage. At each sampling date for each cultivar, the concentrations of galacturonic acid (GA), galacturonic methyl esters, and cell wall neutral sugars were determined for both water-soluble and water-insoluble cell wall substances. For both cultivars, the GA content of water-soluble materials increased during storage, but the GA content of water-insoluble substances decreased, reflecting decreases in pectin size. The percent methyl ester content did not change for either cultivar. Cell wall neutral sugar concentrations declined in the order glucose ≫ galactose > xylose > rhamnose > mannose > arabinose > fucose. Changes in cell wall neutral sugars were minimal and were not observed in both cultivars. For both cultivars, the few cell wall sugar changes that occurred over time were best fit to a quadratic model. Thus, the only observed change in cell wall components that is known to affect firmness was the decreas...

The effects and optimum levels of tetrasodium pyrophosphate (TSPP), alginate and calcium sulfate (CaSO 4 ) on physical and sensory characteristics of texturized sweetpotato puree were studied using response surface methodology. Samples were subjected to instrumental texture profile analysis (TPA) and sensory evaluation. Prediction models to describe the effects of ingredients on TPA parameters were used to generate contour plots for optimization using TPA values of baked roots as the limits. The optimum formulations having textural characteristics of the baked roots were within the following identified regions : (a) at 0.12% TSPP, alginate, 0.20-0.25%, and CaSO 4 , 0.40-0.70% ; (b) at 0.18% TSPP, alginate, 0.20-0.55%, and CaSO 4 , 0.22-0.42%. A taste panel scored representative formulations of the optimum regions similar to the baked roots for color, flavor, texture, and overall acceptability.

We evaluated the physical and sensory characteristics of restructured sweetpotato puree texturized with methylcellulose (MC) or methylhy-droxypropylcellulose (MHPC). Samples were studied by instrumental texture profile (TPA), dynamic rheometric and sensory analyses, and scanning electron microscopy. Gelation of the gum-puree mixtures gave maximal values of the storage modulus (G') at 60-70°C. The TPA curves measured at 60°C for the 0.50%MC or MHPC sample were similar to those of baked sweet potatoes (control). A texture profile panel rated the 60°C samples of the 0.25-0.50%MC or MHPC product as nearly equal to baked roots for several texture notes. An untrained acceptability panel scored the 0.25%MC and MHPC samples significantly higher in flavor and overall acceptability than baked roots.

Sweetpotato strips vacuum-infiltrated with 0.01-0.15M solutions of Na 3 PO 4 , Na 2 CO 3 , NH 4 OH, or NaOH prior to heat processing were firmer than untreated, heat-processed strips. Among the bases Na 3 PO 4 and Na 2 CO 3 were most effective. When base-treated, cooked tissue was adjusted to its normal pH range (5.9-6.2) and reheated, the retention of firmness did not decrease. Using calcium chloride solution in conjunction with base treatment further increased firmness retention. This process was applied on strips but could readily be adapted to other types of sweetpotato products ranging from dice to chunks

‘Jewel’ sweet-potato slices 0.5 cm thick were precooked at 100, 125 and 150C for varying periods of time, finish-cooked for 15 min at 150C, and pureed. Selected chemical and physical properties of the purees were compared to a puree prepared from conventionally baked sweet potatoes (1.25 h at 195C). Purees from the controlled heat process were also compared to the baked puree by a sensory panel. Of all the treatments, puree from the 100C, 6-min precook treatment was the most silimar to puree from baked sweet potatoes with respect to chemical and physical characteristics. The sensory panel found the two purees to be different, but were equally divided when asked to express a preference. Subsequent analysis showed that the starch of the baked control had been more completely hydrolyzed than the starch of the other treatments. This was reflected by higher maltose, lower starch content and by decreased starch molecular size and viscosity of the control compared with the other treatments.

The softening of a French fry-type product prepared from‘Jewel’ sweetpotatoes decreased linearly (P ≤ 0.01) when the tissue pH was incrementally lowered from ca. 6 to 3.8 prior to blanching. Tissue pH was decreased by vacuum infiltration of a series of organic and mineral acids of 0.01 to 0.4M. Firmness retention decreased when the ionic strength of the acidulant was increased by addition of NaCl. The structures of the pectic substances were affected by the tissue pH and starch hydrolysis decreased as tissue pH decreased from its normal value of ca. 6, reflecting partial inactivation of endogenous amylolytic enzymes.

Pickling cucumber fruits were stored at 15.5°C and either 62 or 93% relative humidity (rh) for 28 days. Periodically, fruits were removed from both treatments, and weight loss was measured. Mesocarp tissue was analysed for osmotic potential, relative water content, membrane leakage, concentration of acids, sugars, and free amino acids, and cell wall composition.

Wound healing in cucumber fruit (Cucumis sativus L., cv. Calypso) was studied using histological and degradative techniques. A thick exudate appeared at the wounded surface shortly after wounding. This material retarded water loss and possibly aided in the formation of sclerified parenchyma observed 24 hours after wounding. The sclerified material was positive to a modified Weisner stain, indicating lignification was occurring. Wound periderm (cork) was initiated directly beneath the sclerified parenchyma cells within 48 hours after wounding. The cork layers were positive to Sudan IV stain, indicating suberin was being formed. The rate of phellem development decreased by 6 days after wounding. By day 7, younger phellem cells and sclerified parenchyma cells were stained by Sudan IV. Degradation of the wound tissue by chemical procedures demonstrated that relatively large amounts of lignin and suberin were deposited during healing. Fragments from the lignin degradation Indicated that lignin was composed mainly of gualacyl and p-hydroxyphenyl residues. Suberin was found to contain mainly 1,16-hexadecane and 1,18-osctadecene decarboxylic acids detected as the silylated diol derivatives. Wound healing by plants has significant theoretical and prac- tical impact. Successful postharvest storage of plant organs de- pends on the ability of the plant material to resist invasion by pathogenic microorganisms. Commercially important plant or- gans generally are wounded during harvest and handling before storage. The frequency and severity of wounding varies with the 'nature of the harvested material, the environmental condi- tions during harvest, and the implements used for harvest and transporation. Since wounds can serve as avenues for microbial attack and moisture loss, rapid wound healing is required if organ decay and/or desiccation are to be avoided. Wound responses differ with regard to plant species and organ (El Hadidi, 1969; Rittinger et al., 1987). In many dicotyledons, wounds are closed by deposition of biopolymers in cells adja- cent to the wounded area, followed by formation of a wound periderm or cork beneath the sealed area. The deposited material has been shown, in some cases, to be suberin (Cottle and Ko- lattukudy, 1982) and lignin-like in others (Walter and Schadel, 1983). Suberin is believed to contain an aromatic domain, lig- nin-like in nature, that is covalently bonded to the cell wall and an aliphatic domain bonded to the aromatic regions (Kolattu- kudy, 1984). Suberized tissue generally has an affinity for lipid stains such as Sudan IV and, upon reductive depolymerization with Li Al H4, yields a family of mono- and di-alcohols with carbon chain lengths ranging from C16 through C30. Lignified tissue has little affinity for Sudan IV stain, but is highly reactive with Weisner stain (Walter and Schadel, 1983). Reductive de- polymerization yields only small amounts of mpno- and di-al- cohols, while alkaline oxidation gives relatively large amounts of p-hydroxybenz aldehyde and vanillin. Alkaline oxidation of suberized tissue gives similar degradation products, Thus, using

The sugar content of five sweetpotato [Ipomoea batatas (L.) Lam.] cultivars (`Centennial', `Cordner', `Georgia Red', `Jewel', and `Sweet Red') was measured by high-performance liquid chromatography (HPLC) and compared to the sugar content of the cellular sap measured by refractive index (RI). The HPLC and RI sugar contents were measured at harvest, after curing, and during storage. Changes in the sugar content, as determined by the RI, were found to be linearly related to changes in the sugar content of cell sap and tissue, as measured by HPLC, indicating that this method can be used to monitor changes in postharvest total sugar content.

A French-fry-type product was prepared from ‘Jewel’ and ‘Centennial’ sweet potatoes. Samples were prepared from freshly harvested, cured, and stored, cured roots. The roots were peeled, sliced into strips and blanched in hot water. The blanched strips were partially dehydrated by one of five treatments and then frozen at −30°C. Frozen strips were fried in hot peanut oil and evaluated by a sensory panel. Strips prepared by dehydration in a hot air tunnel at 120°C for 5 min were favored by the sensory panel. Blanching removed significant amounts of dry matter and resulted in partial hydrolysis of the starch by endogenous enzymes. Sensory color scores were not affected by reducing sugar content. Sensory flavor scores were related to total sugar content.

Heat penetration effects on sweet potato tissue resulting from three lye peeling treatments were evaluated using light and scanning electron microscopy. Heat-mediated starch gelatinization, cell wall separation, chromoplast disruption, and enzymatic discoloration were observed in varying degrees according to the peeling treatment. Starch gelatinization, cell wall separation, and chromoplast disruption decreased in the order: 15-min peel; 30-min pre-soak (water 78–83°C), followed by a 6-min peel; 6-min peel. Discoloration occurred in significant amounts only in the 6-min peel because heat penetration was sufficient to disrupt lacticifer organization but insufficient to inactivate the polyphenol oxidase (PPO) enzyme. The 30-min pre-soak, 6-min peel treatment provided the most attractive finished product.

‘Jewel’ and ‘Centennial’ sweet potatoes were processed into frozen patties at harvest, after curing I wk, and after curing and storing up to 26 wk. Sugar, starch, and pectin contents were determined on raw roots, cooked slices, and finished patties. The starch content after cooking was correlated with consumer acceptance and is the most important factor in the preparation of a patty of consistent quality from both fresh and stored roots. Scanning electron microscopy showed that in the cooked, pureed sweet potatoes most of the cells had been ruptured and that the patty was held together by an amorphous matrix consisting of added ingredients and spilled cellular contents.

A population of 100 sweet potato seedlings from 7 parent clones was grown for one season in order to evaluate root protein quantity and quality. Protein content of the 100 seedlings ranged from 4.38% to 8.98% with a mean of 6.29%; the 7 parents ranged from 4.96% to 6.53% with a mean of 5.72%. The mean of the seedlings was not significantly different from that of the parents. The 10 seedlings with highest protein (7.40% to 8.98%) were selected for further study of protein quality. Levels of nonprotein nitrogen (NPN) in these high protein selections were not significantly different from those of the parents. The correlation between the percentage of protein and the percentage of NPN was low (r = 0.30). The amino acid pattern in the high protein selections differed significantly from the parents with lower levels of valine, cysteine, methionine, tyrosine, and phenylalanine. Trypsin inhibitor activity (TIA) levels in the selected seedlings did not vary significantly from the parents. TIA and the percentage of protein were not significantly correlated (r = 0.15). The results indicate it is possible to obtain high protein cultivars without increasing the percentages of NPN and TIA. With the exception of valine, the aromatic and sulfur-containing amino acids, the overall protein quality was not changed in the seedlings with increased protein content.

A process using a commercial alpha amylase was developed for producing consistent sweet potato puree independent of age or seasonal variations in the raw roots. The process includes thermal gelatinization of the puree starch, enzyme hydrolysis of a portion of the puree, and subsequent blending of the enzyme-treated portion with the untreated portion. Alcohol insoluble solids decreased as the percentage of enzyme-treated puree in the mixture was increased. Chemical and rheological differences comparing purees made from fresh and stored roots became insignificant when the proportion of enzyme-treated puree was greater than 75%. Sensory texture differences were insignificant if the proportion was greater than 50%.

The α-amylase of the thermophile Bacillus stearothermophilus 1518 was used as a model enzyme to examine the heat resistance of a bacterial amylase at ultrahigh temperature in a starch-based pudding. When heated in the laboratory pudding at 143°C for the equivalent of 22.2 set, approximately 26% of the initial amylolytic activity was retained. The presence or absence of individual ingredient groups (starch, caseinate-nonfat dry milk, oilemulsifiers, salts, or sucrose) of the pudding had no significant effect on amylase heat resistance. A combination of any two of the starch, caseinate-nonfat dry milk, or oil-emulsifier ingredients were found to be important for thermostability. The amylase of the mesophile Xanthomonas campestris 13957–2 exhibited similar thermal inactivation characteristics.

Concentrated cultures of Lactobacillus bulgaricus were prepared by resuspending cells grown in semisynthetic media in sterile 10% non-fat milk solids. The concentrated cultures were frozen in liquid nitrogen for 24 h. The cell suspensions exhibited decreased viability after storage, and the amount of death varied among the different strains tested. Storage stability of all strains examined was improved by supplementing the growth medium with sodium oleate. Radioisotopes were used to study the fate of sodium oleate with L. bulgaricus NCS1. [1- 14 C]sodium oleate was incorporated solely into the lipid portion of the cells, including both neutral and polar lipids. The fatty acid composition of L. bulgaricus NCS1, NCS2, NCS3, and NCS4 grown with and without sodium oleate was studied. The major fatty acids of strains NCS1, NCS2, and NCS3 grown without sodium oleate were dodecanoic, tetradecanoic, hexadecanoic, hexadecenoic, and octadecenoic acids. In addition to these, strain NCS4 contained C 19 cyclopropane fatty acid. The major fatty acids of all strains grown with sodium oleate were tetradecanoic, hexadecanoic, hexadecenoic, octadecenoic, and C 19 cyclopropane fatty acids. All strains grown in broth containing sodium oleate contained larger amounts of octadecenoic and C 19 cyclopropane fatty acid, and less saturated fatty acids than when grown without sodium oleate. Statistical analyses indicated that C 19 cyclopropane fatty acid was most closely related to stability of the lactobacilli in liquid nitrogen. A negative regression line that was significant at P < 0.001 was obtained when the cellular content of this fatty acid was plotted against death.

Roots of three sweet potato [Ipomoea batatas (L.) Lam] cultivars, Centennial, Jewel, and Pope, were harvested at three soil temperature ranges, cured for 1 to 7 days at 30°C and 90% to 95% RH, and stored at 13° to 13.5° and 90% and 95% RH. Wound healing during curing was evaluated using a rapid color test and histochemical methods. The color test was a good indicator of the lignification phase of wound healing for ‘Centennial’ and ‘Jewel’, and a fair indicator for ‘Pope’. Wound healing rates for the cultivars were similar. Roots harvested from the warmest soils (22° to 25°) had higher color scores (most wound lignification) up to 3 days of curing. After 5 days, there were ≈2.7 layers of lignified cells and one layer of wound periderm. After 16 weeks of storage, roots harvested at soil temperatures of 10° to 12° and 22° to 25° had lost more weight and developed more rots than did roots harvested at 15° to 17°, despite the fact that wound healing progress was similar. Thus, factors other than wound healing strongly influence storage stability.

In a two-year study, the flavor and texture profiles and carbohydrate composition of cured, baked‘Jewels’sweet potatoes were compared to baked, uncured‘Jewels’sweet potatoes. Curing increased the rate of production of flavor notes and only slightly influenced development of “moist” mouthfeel. Given sufficient time after harvest, baked, cured roots were indistinguishable from baked, uncured roots. Carbohydrate content was not a sensitive indicator of post-harvest treatment since no statistically significant differences were detected between cured and uncured roots.

Four sets of sweet potato clones obtained by meristem tip culture were used to investigate the effect of feathery mottle virus (FMV) infection on the appearance, sensory quality and chemical composition of the storage roots. This study, encompassing four generations, indicated that FMV infection had a slight effect on carbohydrate metabolism but no effect on the polyphenoloxidase-phenol system. Flavor and texture profile analyses indicated that for one clone, FMV-infected roots were more desirable when baked than healthy roots. Considering the study as a whole, FMV infection did not appear to adversely affect sweet potato sensory properties. Clones produced from the same parent by meristem tip culture might have different compositional and sensory properties.

Sweet potato flakes supplemented with soy flour, soy flour plus DL-methionine, cottonseed flour and wheat gluten flour were prepared. The fortified flakes had higher protein calorie to total calorie ratios but had lower water-binding capacity than flakes with no supplementary material. The amino acid pattern of soy flour, soy plus methionine and cottonseed flour formulations compared favorably with that of non-supplemented flakes. Each formulation was stored at 23° and 40°C under nitrogen for 8.25 months. Although the levels of several amino acids appeared to change significantly during storage, only glycine in the gluten formulation linearly decreased. Tyrosine in the soy formulation appeared to increase during storage. Flakes stored at 40°C appeared to develop off flavors and to lose water-binding capacity.

Freshly harvested sweet potatoes [Ipomoea batatas (L.) Lam. c. Jewel] are cured by holding them at 80–95% relative humidity and 29.4°C for 5 to 7 days. Curing heals wounds inflicted during harvest, thus minimizing loss from microbial decay during subsequent storage. The wound healing process was followed by applying a saturated solution of phloroglucinol in strong acid (PG) to the underside of detached wound tissue and scoring the intensity of the color developed. Microscopic examination of companion tissue with PG showed that color intensity was due to the layers of cells in which PG positive material was deposited. Wound periderm formation was observed to occur simultaneously with development of the most intense color, indicating that the test may be useful in the evaluation of curing progress.

Methods of eliminating color quench in measuring radioactivity of carotenes by liquid scintillation spectrometry were studied. Solutions containing internal 14 C standards and 1 mg of lycopene or beta carotene were counted with about 0.5% efficiency. The pigments were decolorized in a counting vial using benzoyl peroxide and light. After 1–3 hours of decolorization of the pigments, counting efficiencies of over 80% were obtained in PPO-POPOP phosphor. Similar results were obtained in counting 14 C carotenes using an external standard to determine efficiency.

Summary Peroral intestinal biopsies progressively lose weight when stored in test tubes at −20 C, resulting in apparent enzyme activities based on tissue weight that are 60% higher after 7 days of storage and 200% higher after 28 days than activities based on protein content. The weight loss and consequent apparent increase in activity can be prevented by wrapping the biopsies in parafilm. This precaution allows tissue weight to be used as satisfactorily as protein content as the basis of expression of enzyme activity.

Oleuropein, the bitter glucoside in green olives, and products of its hydrolysis were tested for antibacterial action against certain species of lactic acid bacteria involved in the brine fermentation of olives. Oleuropein was not inhibitory, but two of its hydrolysis products, the aglycone and elenolic acid, inhibited growth of the four species of lactic acid bacteria tested. Another hydrolysis product, β-3,4-dihydroxyphenylethyl alcohol, was not inhibitory. The aglycone of oleuropein and elenolic acid were much more inhibitory when the broth medium contained 5% NaCl; 150 μg of either compound per ml prevented growth of Lactobacillus plantarum . A crude extract of oleuropein, tested by paper disk bioassay, was inhibitory to 3 of 17 species of bacteria screened, none of which were lactic acid bacteria. The acid hydrolysate of the extract was inhibitory to 11 of the bacteria, which included four species of lactic acid bacteria and other gram-positive and gram-negative species. Neither crude preparation was inhibitory to growth of the seven species of yeasts tested. A possible explanation is given for the previously reported observation that heating (3 min, 74 C) olives prior to brining renders them more fermentable by lactic acid bacteria. Results of a brining experiment indicated that oleuropein is degraded to antibacterial compounds when unheated olives are brined.

Summary Thirty-seven Puerto Rican patients with untreated tropical sprue all had deficiency of intestinal lactase and two-thirds of them also were deficient for sucrase and maltase. A separate group of 48 patients who had been treated for 3 months to 4 years with folic acid or antibacterial agents were found to have no malabsorption, megaloblastic anemia, or intestinal histological abnormalities and their sucrase and maltase activities were normal. However, 63% still had lactase deficiency, a prevalence 3 times that of a control group. Nineteen patients were studied at the time of diagnosis and serially while receiving therapy. After treatment for 3 to 18 months (mean, 11 months) lactase deficiency continued in 75% of patients as the sole residual manifestation of tropical sprue. Thus it appears that this single enzyme deficiency can be caused by prior intestinal disease or current subclinical illness, and findings of such a deficiency in the absence of other clinical illness may warrant evaluation for an underlying intestinal disease.