Overview
Hariono and colleagues compared proximate quality and metal content in soy milk from an Indonesian producer after cooking in aluminum versus stainless-steel vessels. The paper reports very high measured concentrations for lead (Pb), Cu, Zn, mercury (Hg), and As in finished soy milk, with stainless-steel processing lowering Pb, Cu, and Hg relative to aluminum processing but increasing Zn and arsenic (As). The values are routeable as a small cookware-comparison occurrence study for soy milk, but they should be treated cautiously because the paper reports only one value per treatment, does not disclose replicate statistics or LODs, and appears to use comma decimals in the Indonesian format.
Key numbers
Table 1 and Table 2 report the same metal concentrations in finished soy milk, in ppm, after processing with two cooking-vessel materials:
The paper compares Pb to an Indonesian BPOM ready-to-consume beverage limit of 0.05 mg/kg and states that both treatments exceed that threshold. It compares Cu to a cited minimum/normal reference range of 0.8-1.2 ppm and states that both treatments exceed that range. It compares Hg to a cited beverage threshold of 0.005 ppm and states that both treatments exceed that threshold. The paper states that the maximum As limit is 0.05 mg/kg; both reported As values (0.079 and 0.107 ppm) exceed that cited limit.
The same tables report proximate and pH values: total protein 2.590% in aluminum-pan soy milk and 2.340% in stainless-steel-pan soy milk; fat 0.190% and 0.47%; lactose 3.800% and 4.16%; solid non-fat 7.15% and 7.720%; pH 6.943 and 6.710.
The abstract also says cooking water contributed Pb 0.055 ppm, Cu 0.044 ppm, Zn 0.028 ppm, and As 0.156 ppm. The abstract lists “Pb, Cu, Zn, Hg, and As” but provides only four numeric water-contribution values; the missing fifth value is a source-side ambiguity, not filled in here.
Methods (brief)
The study used a descriptive comparison of soy milk processed in aluminum and stainless-steel cooking vessels. The sample was soy milk from one industrial-scale producer in Sumbersari District, Jember Regency, with testing conducted at the Bioscience Academic Implementation Unit of Jember State Polytechnic on July 26, 2022. The paper states that metal analysis covered Cu, Pb, As, chromium (Cr), Zn, and Hg in soy milk, with atomic absorption spectroscopy using the Shimadzu Atomic Absorption Cook Book method; Cr is named in methods but not reported in the result table, so this source page does not list Cr as a measured result. The methods section does not disclose instrument model, digestion details, LOD/LOQ, blank handling, recovery, certified reference material, or replicate statistics.
Implications
This source may support a narrow context note for soy milk and soy-based plant milk where cookware or process water can dominate the measured metal profile. It is not sufficient by itself for a benchmark distribution because the sample structure is a two-condition processing comparison from one producer, not a market survey. The very high Pb and Cu values should be preserved as source facts but should not be generalized without corroborating Indonesian soy-milk occurrence studies or reanalysis with clearer QA/QC reporting.
Related evidence
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