Objective

Assessment of the quantity and chemical type of phosphorus (P) content in cooked ham products with or without preservatives using a novel biochemical procedure.

Methods

We examined the quantity and types of P in 40 samples of cooked ham, including 20 without and 20 with P-containing preservatives, which were purchased randomly from a grocery store in Italy. Food samples were analyzed for dry matter, nitrogen, fat, and P content. Novel spectrophotometric methods were used to measure total P and 3 different P subtypes, that is, water-soluble (inorganic) P including added preservatives and natural P derived from phospholipids and phosphoproteins, separately.

Results

Compared with hams without preservatives, hams with P-containing preservatives had significantly lower dry matter and protein and fat contents. There was 66% more inorganic P (IP) in ham with preservatives than in samples without preservatives (169 ± 36 vs. 102 ± 16 mg/100 g, P < .001, respectively). There were no significant differences in P contents derived from proteins or lipids. The P-to-protein ratio was higher in ham samples with preservatives than in those without preservatives (16.1 ± 4.0 and 9.8 ± 0.8 mg/g, P < .001). The sum of measured IP and P from phospholipids and phosphoproteins was 91% ± 4% of measured total P (207.1 ± 50.7 vs. 227.2 ± 54.4 mg/100 g), indicating a small portion of unspecified P and/or under measurement.

Conclusions

Novel differential dietary P measurement detects added P-containing preservatives. Cooked ham with preservatives has 66% more measurable IP and 64% higher P-to-protein ratio than ham without preservatives. The contribution of food added with P-containing preservatives to global dietary P burden can negatively influence chronic kidney disease outcome and counteract the efficacy of P-binder medications: this is an important topic that warrants additional investigations.

Phosphorus is an important natural nutrient, but high dietary phosphorus intake, including that sourced from added preservatives, is of great concern in renal patients. In this context a reliable analytical method able to quantify differential phosphorus in food could be a valuable tool for monitoring diet composition This paper presents a novel analytical procedure to quantify the following kinds of phosphorus in cooked ham: total (TP), inorganic (IP), from phospholipids (PL), and from phosphoproteins (PP). This technique is based on a suitable sample preparation followed by spectrophotometric analyses. Analytical performances of each method were evaluated, taking advantage also of food industry certified material and in-house reference samples. Limit of detection and limit of quantification values for TP, IP, PP-derived, and PL-derived phosphorus were 13 and 37, 11 and 33, 2 and 20, and 6 and 16 mg P/100 g fresh mass, respectively. Similar results were obtained when this procedure was used to quantify different types of phosphorus present in cooked ham samples. In conclusion, this procedure is effective for quantifying the content of different types of phosphorus present in cooked ham, which can be contributed by different phosphorus-containing ingredients and additives. To the best of the authors' knowledge, this is the first time that simultaneous determination of TP, IP, PL, and PP in cooked ham has been reported.